ACETIC ACID (ASETİK ASİT)
ACETIC ACID (ASETİK ASİT)
CAS No. : 64-19-7
EC No. : 200-580-7
Synonyms:
Acetic acid ; Asetik asit ; Glasiyal , Asetikasit ; Aseticacid ; asetic acid ; asetik acid ; acetik asit ; ethonik asit , etonik asit ; ethonic asit ; etonik acid ; glacial acid , glasiyal acid ; asetik asit glasiyal ; metan karboksilik asit ; methanekarboksilik asit ; methanecarbocsilic acid ;methycarbocsilic acid ;
Acetic Acid Glacial; ACETIC ACID, GLACIAL; Acide acetique; acido acetico, de una concentracion superior al 10 por ciento, en peso, de acido acetico ; Aci-Jel; E 260; ESSIGSAEURE UEBER 10 BIS 40%; ESSIGSAEURE UEBER 40%; Essigsaure; Ethanoic acid; Ethanoic acid monomer; Ethylic acid; Glacial acetic acid; Methanecarboxylic acid; Vinegar acid Vinegar (when dilute); Hydrogen acetate; Methanecarboxylic acid Ethanoic acid ; Acetic acid (aqueous), Ethanoic acid, Glacial acetic acid (pure compound), Methanecarboxylic acid ; Acetic acid; Ethanoic acid; Ethylic acid; Methanecarboxylic acid; Glacial acetic acid; Vinegar acid Acetic acid, methane carboxylic acid; ethanoic acid ; 200-580-7 64-19-7 Acetic acid Acid, Acetic; Acide acétique Acido acetico ättiksyra azido azetikoa azijnzuur CH3CO2H CH3COOH Essigsäure Ethanoic acid; etikkahappo Glacial acetic acid; EINECS 200-580-7; MeCO2H MeCOOH Methanecarboxylic acid; methyl carboxylic acid; MFCD00036152; MFCD00036287; Molybdic acid Octan barnaty Octowy kwas Octowy kwas; Pyroacetic acid; PYROACETIC ETHER; IODINE CHLORIDE; IODINE MONOCHLORIDE; IODINE MONOCHLORIDE SOLUTION, WIJS; IODINE-MONOCHLORIDE, WIJS; IODINE SOLUTION ACCORDING TO WIJS; IODOCHLORIDE; IODOMONOCHLORIDE; WIJ`S IODINE SOLUTION; WIJS` REAGENT; Acetasol; aceticacid(non-specificname); aceticacid(solutionsgreaterthan10%) ; Glacial acetic acid ; Ethanoic acid ; Ethylic acid ;Acetic acid ; Asetik asit ; Glasiyal , Asetikasit ; Aseticacid ; asetic acid ; asetik acid ; acetik asit ; ethonik asit , etonik asit ; ethonic asit ; etonik acid ; glacial acid , glasiyal acid ; asetik asit glasiyal ; metan karboksilik asit ; methanekarboksilik asit ; methanecarbocsilic acid ;methycarbocsilic acid ; Acetic Acid Glacial; ACETIC ACID, GLACIAL; Acide acetique; acido acetico, de una concentracion superior al 10 por ciento, en peso, de acido acetico ; Aci-Jel; E 260; ESSIGSAEURE UEBER 10 BIS 40%; ESSIGSAEURE UEBER 40%; Essigsaure; Ethanoic acid; Ethanoic acid monomer; Ethylic acid; Glacial acetic acid; Methanecarboxylic acid; Vinegar acid Vinegar (when dilute); Hydrogen acetate; Methanecarboxylic acid Ethanoic acid ; Acetic acid (aqueous), Ethanoic acid, Glacial acetic acid (pure compound), Methanecarboxylic acid ; Acetic acid; Ethanoic acid; Ethylic acid; Methanecarboxylic acid; Glacial acetic acid; Vinegar acid Acetic acid, methane carboxylic acid; ethanoic acid ; 200-580-7 64-19-7 Acetic acid Acid, Acetic; Acide acétique Acido acetico ättiksyra azido azetikoa azijnzuur CH3CO2H CH3COOH Essigsäure Ethanoic acid; etikkahappo Glacial acetic acid; EINECS 200-580-7; MeCO2H MeCOOH Methanecarboxylic acid; methyl carboxylic acid; MFCD00036152; MFCD00036287; Molybdic acid Octan barnaty Octowy kwas Octowy kwas; Pyroacetic acid; PYROACETIC ETHER; IODINE CHLORIDE; IODINE MONOCHLORIDE; IODINE MONOCHLORIDE SOLUTION, WIJS; IODINE-MONOCHLORIDE, WIJS; IODINE SOLUTION ACCORDING TO WIJS; IODOCHLORIDE; IODOMONOCHLORIDE; WIJ`S IODINE SOLUTION; WIJS` REAGENT; Acetasol; aceticacid(non-specificname); aceticacid(solutionsgreaterthan10%) ; Glacial acetic acid ; Ethanoic acid ; Ethylic acid ; Methanecarboxylic acid ; Glacial acetic acid; Acetic acid solution; acetic acid 50%; acetic acid, of a concentration of more than 10 per cent, by weight, of acetic acid; Acetic Acid Glacial BP; Natural Acetic Acid; Acetic acid (36%); Acetic acid,food grade; Acetic Acid Glacial; GAA; Acetic Acid, Glacial; Asetik asit; Acide acetique; Acetic Acid; Acetic Acid; Acetik Acit; Asetik acit; asetik acide; acetik asid; asetic acid; asetic acide; Asetikasit; Asetique asit; Acideacetique; AceticAcid; ASETİK ASİT; ACİDE ACETİQUE; ACETİC ACİD; ACETİC ACİD; ACETİK ACİT; ASETİK ACİT; ASETİK ACİDE; ACETİK ASİD; ASETİC ACİD; ASETİC ACİDE; ASETİKASİT; ASETİQUE ASİT; ACİDEACETİQUE; ACETİCACİD; asetik asit; acide acetique; acetic acid; acetic acid; acetik acit; asetik acit; asetik acide; acetik asid; asetic acid; asetic acide; asetikasit; asetique asit; acideacetique; Methanecarboxylic acid ; Glacial acetic acid; Acetic acid solution; acetic acid 50%; acetic acid, of a concentration of more than 10 per cent, by weight, of acetic acid; Acetic Acid Glacial BP; Natural Acetic Acid; Acetic acid (36%); Acetic acid,food grade; Acetic Acid Glacial; GAA; Acetic Acid, Glacial; Asetik asit; Acide acetique; Acetic Acid; Acetic Acid; Acetik Acit; Asetik acit; asetik acide; acetik asid; asetic acid; asetic acide; Asetikasit; Asetique asit; Acideacetique; AceticAcid; ASETİK ASİT; ACİDE ACETİQUE; ACETİC ACİD; ACETİC ACİD; ACETİK ACİT; ASETİK ACİT; ASETİK ACİDE; ACETİK ASİD; ASETİC ACİD; ASETİC ACİDE; ASETİKASİT; ASETİQUE ASİT; ACİDEACETİQUE; ACETİCACİD; asetik asit; acide acetique; acetic acid; acetic acid; acetik acit; asetik acit; asetik acide; acetik asid; asetic acid; asetic acide; asetikasit; asetique asit; acideacetique; aceticacid; Asetik Asit; Acide Acetique; Acetic Acid; Acetic Acid; Acetik Acit; Asetik Acit; Asetik Acide; Acetik Asid; Asetic Acid; Asetic Acide; Asetikasit; Asetique Asit; Acideacetique; Aceticacid
Asetik asit
Asetik asit
Asetik asit-2D-skeletal.svg
Asetik asit-CRC-GED-3D-balls-B.png
Asetik asit-2D-flat.png
Asetik asit-CRC-GED-3D-vdW-B.png
Asetik asit.jpg
IUPAC adı[gizle]
Asetik asit[1][2]
Sistematik ad[gizle]
Etanoik asit
Diğer adlar[gizle]
Sirke (seyrek olduğunda); Hidrojen asetat; Metankarboksilik asit[3][4]
Tanımlayıcılar
Kısaltmalar AcOH
Asetik asit CAS numarası 64-19-7
PubChem 176
Asetik asit EC numarası 200-580-7
Asetik asit UN numarası 2789
DrugBank DB03166
KEGG D00010
MeSH Acetic+acid
Asetik asit ChEBI 15366
RTECS numarası AF1225000
SMILES
[göster]
Beilstein 506007
Gmelin veritabanı 1380
ChemSpider 171
3DMet B00009
Asetik asit Özellikler
Asetik asit Kimyasal formül C2H4O2
Asetik asit Molekül kütlesi 60,05 g mol-1
Asetik asit Görünüm Renksiz sıvı
Asetik asit Koku Keskin, sirke gibi
Asetik asit Yoğunluk 1.049 g cm-3
Asetik asit Erime noktası
16-17 °C; 61-62 °F; 289-290 K
Asetik asit Kaynama noktası
118-119 °C; 244-246 °F; 391-392 K
Asetik asit Çözünürlük (su içinde) Karışabilir.
log P -0.322
Asitlik (pKa) 4.76[5]
Baziklik (pKb) 9.24 (Asetat iyonunun bazikliği)
Tehlikeler
NFPA 704
NFPA 704.svg230
Parlama noktası 40 °C (104 °F; 313 K)
Öztutuşma
sıcaklığı 427 °C (801 °F; 700 K)
Patlama sınırları 4-16%
ABD maruz
kalma limiti (PEL) TWA 10 ppm (25 mg/m³)
LD50 3.31 g kg-1, oral (sıçan)
Belirtilmiş yerler dışında verilmiş olan veriler, Standart sıcaklık ve basınçtadır. (25 °C, 100 kPa)
Bilgi kutusu kaynakları
Asetik asit veya etanoik asit CH3COOH formüllü bir organik asittir, sirkeye ekşi tadını ve keskin kokusunu vermesiyle bilinir. Karboksilik asitlerin en küçüklerindendir (en küçük olan formik asittir). Doğada karbonhidratların yükseltgenmesiyle oluşur. Sanayide asetik asit hem biyolojik yolla hem de sentetik yolla imal edilir. Tuz ve esterine asetat denir. Suda tamamen çözünür.
Kullanımı
Sirke
Sirke genelde %4-5 oranında asetik asit içerir ama turşu kurmak için kullanılan sirkelerde bu oran %18'e varır. Sirkenin oluşturduğu asitli ortam gıdaların bozulmasına neden olacak çoğu mikroorganizmanın büyümesini engeller. Bu yüzden turşulama sebzelerin ömrünü uzatmak için etkili bir yöntemdir.
Sanayi
Donmuş asetik asit
Sanayide asetik asitin geniş bir kullanım alanı vardır, çoğu kimyasalın üretiminde hammadde olarak kullanılır. En önemli kullanımı vinil asetat üretimidir ve bundan elde edilen polivinil asetat tahta tutkalı olarak kullanılır. Bunu asetik anhidrit ve asetik ester üretimi izler. Sirke üretiminde kullanımı nispeten önemsizdir. Asetik asitin bir diğer önemli kullanımı çözücü olaraktır. PET plastiklerin üretiminde kullanılan tereftalik asit üretiminde asetik asit çözücü olarak kullanılır, bu kullanım asetik asitin tüm kullanımının %5-10'unu oluşturur. Asetik asit gıda sanayisinden tampon özelliğinden dolayı E260 adıyla bir katkı maddesi olarak kullanılır.
Asetik asidin türevlerinin de çeşitli kullanımları vardır. Örneğin, Sodyum asetat dokuma sanayinde ve gıda katkı maddesi olarak (E262) kullanılır. Selüloz asetat fotoğraf filmi üretiminde kullanılır.
Asetik asidin zayıf bir asit olması onun özellikle ev içinde temizleme amacıyla kullanılmasının nedenidir. Seyreltik asetik asit (sirke) çaydanlıkların kireçten arındırılmasında, cam ve diğer parlak yüzeylerdeki madenî birikmeleri temizlemekte kullanılabilir.
Etkileri
Emniyet ikazı
Yoğun asetik asit cildi yakar, göze kalıcı zarar verir ve ciltte kabarcıklar oluşmasına neden olur. Etkileri birkaç saat sonra hissedilir. Bu etkilerden korunmak için nitril koruma eldivenleri giyilir . Asetik asit 39 °C üzerinde tutuşabilir, havayla patlayıcı karışımlar oluşturabilir.
%25'den daha yoğun asetik asit labarutuarlarda çekerocak altında kullanılmalıdır. Seyreltik asetik asit zararsızdır, ama daha kuvvetli çözeltileri insan ve hayvanlar için zararlıdır. Sindirim sistemine ciddi hasar verebilir ve kan asitliğini ölümcül oranda değiştirebilir.
ASETİK ASİT
Görünümü : Renksiz Sıvı Haldedir.
Kimyasal Adı : E260, Sirke Asidi, Etanoik Asit
Kimyasal Formülü : CH3COOH
Ambalaj Şekli : 60 kg. lık Bidonlarda, 1 Tonluk Konteynerlarda
Tanımı ve Kullanım Alanları :
Sanayide biyolojik ve sentetik yollar ile imal edilir. Tuz ve esterine asetat denir. Suda tamamen çözünür. Zayıf bir asittir. Asetik asidin glasiel asetik asit türü % 99,5 saf asetik asit içermektedir. Asetik asidin bu % 99,5'lik glasiel formu 17°C'de katılaşır ve kristalimsi buz taneciklerine benzer bir yapı oluşturur.
Kullanım Alanları
Sirke imalatında kullanılır. Ayrıca turşu yapımında mikroorganizmaların oluşmasını engelleyerek sebzelerin bozulmasını engeller.
Sanayide çoğu kimyasalın üretiminde hammadde olarak kullanılır. Özellikle vinil asetat üretiminde kullanılır, bundan elde edilen polivinil asetat tahta tutkalı olarak kullanılır.
Çözücü olarak sanayide kullanılır. Örneğin, PET plastiklerin üretiminde kullanılan tereftalik asitin üretiminde çözücü olarak kullanılır. Bu kullanım asetik asitin tüm kullanımı içerisinde %5-10 oranındadır.
4. Gıda sektöründe tampon olarak kullanılır. Asitlik sağlayıcı, koruyucu, lezzet verici olarak kullanılır.
Asetik asit, etanoik asit ya da sirke asidi olarak ta anılan, CH3COOH açık formüllü, C2H4O2 kapalı formüllü organik bir asittir. Sirkenin keskin kokusunu ve ekşi tadını veren asittir. Karboksilik asitler arasında en önemlisi ve en küçüğüdür. Karbonhidratların doğada yükseltgenmesiyle elde edilir. Sanayi sektöründe biyolojik ve sentetik olarak elde edilebilir. Suda tamamen çözünen asetik asidin tuz ve esterine asetat adı verilir. Kimya sektöründe etanoik asit olarak anılır. Saf asetik asit keskin, renksiz, iğneleyici bir kokuda olup, 118 derecede kaynar, 16,7 derecede donar. Suya karıştığında suyu çeker, cildi tahriş eder ve metalleri aşındırır. Şarap ya da mayanın mayalanmasıyla elde edilen sirkenin temel maddesi asetik asittir.
Asetik asidin elde edilmesi
Bazı meyve sularında bulunan şeker mayaların etkisiyle birlikte etil alkole dönmektedir. Bu alkol de micoderma denen bakteriyle asetik aside dönüşmektedir. Bu yöntemin dışında asetik asit, etil alkolün oksidasyonuyla, metil alkol reaksiyonuyla elde edilebilir. Eczacılık alanında asetik asit en önemli kimyasaldır. Örneğin aspirin üretiminde kullanılır. Mikrop ve haşere öldüren bakır asetat ile bakır aseto arsenitin başlangıç maddesi asetik asittir. Selüloz triasetat üretiminde kullanılır. Bundan asetat iplikleri oluşturulur. Bunlardan da fotoğraf filmi, ışığı geçiren kağıtlar elde edilir. Yine asetik asitten üretilen etil asetat vernik üretiminde kullanılmaktadır. Matbaa sektöründe kullanılan metal asetatların da başlangıç maddesidir.
Asetik asidin kullanım alanları
Sirke yapımında: Sirkenin içeriği ortalama % 4-5 oranında asetik asit içermektedir. Turşu yapımında kullanılan sirkelerde ise, % 18 oranında asetik asit bulunabilir. Sirke oluşturduğu asitli ortam nedeniyle, besinlerin bozulmasına neden olan mikroorganizmaların büyümesini engellenmektedir. Turşu yapımında gıdaların ömrünü uzatmak için, sirke kullanımı oldukça etkilidir.
Sanayi sektöründe: Sanayide oldukça geniş bir kullanımı olan asetik asit, kimyasalların üretiminde hammadde olarak değerlendirilir. Vinil asetat üretiminde yoğun şekilde kullanılır. Bundan tahta tutkalı elde edilir. Asetik ester ve asetik anhidrit üretiminde de yararlanılır. Ayrıca çözücü olarak kullanılır. Pet plastik üretiminde kullanılan tereftalik asidin üretiminde çözücü olarak kullanılmaktadır. Bu asetik asidin kullanımının yaklaşık % 5-10 kadarını oluşturur. Gıda sektöründe tampon özelliği olduğundan, E260 olarak katkı maddesi olarak kullanılmaktadır. Bunun türevleri de farklı alanlarda kullanılmaktadır. E262 adıyla dokuma sektöründe ve gıda katkısı olarak sodyum asetat kullanılır. Fotoğraf filmi üretiminde selüloz asetat kullanılır. Zayıf bir asit olduğundan, ev temizliğinde yararlanılır. Özellikle çaydanlıkların kireçlerinin temizlenmesinde, parlak yüzeylerde ve camlardaki madeni birikimlerin temizlenmesinde kullanılır.
Asetik asit kullanılırken dikkat edilmesi gerekenler
Yoğun şekilde kullanımı cildi tahriş eder, gözlerde kalıcı hasarlar oluşturabilir, ciltte kabarcıklar meydana getirir. Kullanımdan sonra birkaç saatte bu etkiler görülebilir. Korunmak için nitril eldivenler kullanılmalıdır. 39 derecenin üzerinde tutuşma özelliği vardır. Bu nedenle havayla patlayıcı karışımlar meydana getirebilir. Yoğunluğu % 25 ten fazla olduğunda, keskinliği ve yakıcılığıyla laboratuvarda kullanılması çok zor olur. Seyreltilmiş asetik asit genellikle zararsızdır. Ancak kuvvetli çözeltiler sindirim sistemine hasar verebilir, kandaki asitliği ölümcül seviyede değiştirebilir.
Asetik asit ya da Avrupa Birliğinin verdiği adıyla E260 bitki ve hayvan dokularında doğal olarak bulunan bir organik asittir. Sirkenin başlıca bileşeni olan asetik asit ticari olarak bakteriyel fermentasyon ya da metanoldan kimyasal sentez yoluyla elde edilmektedir. Kimyada bilinirliği çok eski zamanlara dayanan asetik asit ilk defa 8. yüzyılda müslüman bilim adamı Cabir bin Hayyan tarafından sirkeden distilasyon yoluyla konsantre edilerek üretilmiştir. Gıda sanayinde katkı maddesi olarak ve sirke üretiminde kullanılan asetik asit kimya sanayinin çok önemli bir hammaddesidir. Yapışkan, boya ve çeşitli plastiklerin üretiminde kullanılan bileşiklerin elde edilmesinde asetik asit reaktif madde ya da çözücü olarak işlev görmektedir. Gıdalarda kullanımı ile ilgili bir sınırlama olmayan asetik asit ABD Gıda ve İlaç Dairesi tarafından katkı maddeleri için oluşturulan GRAS (Genellikle Güvenli Kabul Edilir) listesinde yer almaktadır.
ASETİK ASİT(ACETIC ACID)
Sistemik olarak adlandırılan etanoik asit olan asetik asit, CH3COOH (CH3CO2H veya C2H4O2 olarak da yazılır) kimyasal formülüne sahip renksiz bir sıvı organik bileşiktir. Seyreltilmemiş zaman, bazen buzlu asetik asit denir. Sirke, hacimce% 4'ten az asetik asittir, asetik asit, sudan başka sirkenin ana bileşenini oluşturur. Asetik asit, kendine özgü bir ekşi tadı ve keskin kokusu vardır. Ev sirkesine ek olarak, esas olarak polivinil asetat ve selüloz asetatın bir öncüsü olarak üretilir. Çözeltide sadece kısmen ayrıştığı için zayıf bir asit olarak sınıflandırılır, ancak konsantre asetik asit aşındırıcıdır ve cilde saldırabilir. Asetik asit ikinci en basit karboksilik asittir (formik asit sonrası). Bir karboksil grubuna bağlı bir metil grubundan oluşur. Öncelikle fotografik film için selüloz asetat, ahşap tutkalı için polivinil asetat ve sentetik elyaf ve kumaş üretiminde kullanılan önemli bir kimyasal reaktif ve endüstriyel kimyasaldır. Hanelerde, seyreltilmiş asetik asit, kireç çözücü ajanlarda sıklıkla kullanılır. Gıda endüstrisinde, asetik asit gıda katkı maddesi kodu E260 tarafından bir asit düzenleyici ve bir baharat olarak kontrol edilir. Biyokimyada, asetik asitten türetilen asetil grubu, tüm yaşam formları için temeldir. Koenzim A'ya bağlandığında, karbonhidrat ve yağ metabolizmasının merkezinde yer alır. Asetik asit için küresel talep yılda yaklaşık 6,5 milyon mt (Mt / a) olup, bunun yaklaşık 1.5 Mt / a geri dönüşüm ile karşılanmasıdır; geri kalan kısım metanolden üretilmiştir. Sirke çoğunlukla fermantasyon ve daha sonra etanolün oksidasyonu ile üretilen, çoğunlukla seyreltik asetik asittir.
Asetik asit en basit karboksilik asitlerden biridir. Plastik meşrubat şişeleri, fotoğraf filmi üretiminde kullanılan önemli bir kimyasal reaktif ve endüstriyel kimyasaldır; ve ahşap tutkalı için birçok sentetik elyaf ve kumaş için polivinil asetat. Evlerde seyreltilmiş asetik asit genellikle temizlik maddesi olarak kullanılır. Gıda endüstrisinde asetik asit bir asit düzenleyici olarak kullanılır. Asetik asitten türetilen asetil grubu, neredeyse tüm yaşam formlarının biyokimyası için temeldir. Koenzim A'ya bağlandığında, karbonhidrat ve yağ metabolizmasının merkezi olur. Bununla birlikte, hücrelerde serbest asetik asitin konsantrasyonu, hücre içeriğinin pH'ının kontrolünü bozmaktan kaçınmak için düşük bir seviyede tutulur. Asetik asit, bazı bakteriler, özellikle de Acetobacter cinsi ve Clostridium acetobutylicum tarafından üretilir ve dışarı atılır. Bu bakteriler genel olarak gıda maddelerinde, suda ve toprakta bulunurlar ve asetik asit, meyveler ve diğer bazı gıdalar bozulduğunda doğal olarak üretilir. Asetik asit aynı zamanda insanlarda ve diğer primatların vajinal yağlanmasının bir bileşenidir ve hafif bir antibakteriyel madde olarak hizmet ettiği görülmektedir. Asetik asitin metabolizmanın doğuştan gelen bir hatası olan fenilketonüri ile ilişkili olduğu bulunmuştur.
Etanoik asit olarak da bilinen asetik asit, sirke ekşi tat ve keskin kokusunu vermek için en iyi tanınan organik bir kimyasal bileşiktir. En basit karboksilik asitlerden biridir (ikinci en basit, formik asit sonrası) ve CH3COOH kimyasal formülüne sahiptir. Saf, asetik asit olarak adlandırılan saf, su içermeyen durumunda, renksiz, higroskopik bir sıvıdır ve 16,7 ° C'nin (62 ° F) altında renksiz bir kristalin katıya kadar donar. Aşındırıcıdır ve buharı gözleri tahriş eder, burunda yanma hissi yaratır ve boğaz ağrısına ve akciğer tıkanıklığına yol açabilir. Asetat terimi, karboksilat anyonuna (CH3COO-) veya asetik asidin tuzlarından veya esterlerinden herhangi birine başvururken kullanılır.
Bu asit, çeşitli sentetik liflerin ve diğer polimerik malzemelerin üretimi için yararlı olan önemli bir kimyasal reaktif ve endüstriyel kimyasaldır. Bu polimerler arasında esas olarak meşrubat şişelerinde kullanılan polietilen tereftalat; çoğunlukla fotografik film için kullanılan selüloz asetat; ve ahşap tutkalı için polivinil asetat. Hanelerde, seyreltilmiş asetik asit, kireç çözücü ajanlarda sıklıkla kullanılır. Gıda endüstrisi, bir asitlik düzenleyici olarak (E260 gıda katkı maddesi kodunun altında) kullanır.
TERMİNOLOJİ
Asil asidin önemsiz adı, Uluslararası Saf ve Uygulamalı Kimya Birliği (IUPAC) tarafından en çok kullanılan ve resmen tercih edilen isimdir. Bu isim asetil, sirke için Latince kelimesinden türemiştir. Eşanlamlı etanoik asit, bazen kimyasal isimlendirmeye girişlerde kullanılan sistematik bir isimdir.
Buzlu asetik asit, su içermeyen asetik asit için önemsiz bir isimdir. Eisessig (tam anlamıyla buz sirkesi) Alman ismine benzer şekilde, isim 16.7 ° C'de (yaklaşık 62 ° F) oda sıcaklığının biraz altında olan buz benzeri kristallerden gelmektedir.
Asetik asit için en yaygın ve resmi kısaltma, AcOH grubu CH3 - C (= O) -; olduğu AcOH veya HOAc'dir. Asit-baz reaksiyonları bağlamında, genellikle Acinstead'in asetat anyonunu (CH3COO-) temsil ettiği, ancak bu kullanımın yanıltıcı olduğu düşünülürse, HAc kısaltması kullanılır. Her iki durumda da, Ac kimyasal element aktinyumunun kısaltması ile karıştırılmamalıdır.
Asetik asit, CH2O ampirik formülüne ve C2H4O2 moleküler formülüne sahiptir. İkincisi genellikle yapısını daha iyi yansıtmak için CH3-COOH, CH3COOH veya CH3CO2H olarak yazılır. Asetik asitin H + kaybından kaynaklanan iyon, asetat anyonudur. Asetat, aynı zamanda, bu anyonu içeren bir tuzu veya asetik asidin bir esteri anlamına da gelebilir.
TARİHÇE
Sirke, medeniyetin kendisi kadar eskidir, belki daha yaşlıdır. Asetik asit üreten bakteriler tüm dünyada mevcuttur ve bira veya şarabın demlenmesini sağlayan herhangi bir kültür kaçınılmaz olarak bu alkollü içeceklerin havaya maruz kalmasının doğal sonucu olarak sirke keşfettiler.
Kimyada asetik asit kullanımı antikliğe kadar uzanır. Üçüncü yüzyılda, Yunan filozof Theophrastos, sirkenin, bakır (II) asetat içeren bakır bir bakır tuzları karışımı olan beyaz kurşun (kurşun karbonat) ve verdigris de dahil olmak üzere, sanatta yararlı pigmentler üretmek için metaller üzerinde nasıl hareket ettiğini tarif etmiştir. Eski Romalılar, sapa adı verilen çok tatlı bir şurup üretmek için kurşun tencerede asitli şarap kaynatmışlardı. Sapa, Roma aristokrasisi arasında kurşun zehirlenmesine katkıda bulunan, kurşun şeker veya Satürn şeker gibi tatlı bir madde olan kurşun asetat açısından zengindi. Sekizinci yüzyıl Farsça simyacı Jabir Ibn Hayyan (Geber), asetik asidi sirkeden distilasyon yoluyla konsantre etti.
Rönesansta, buzlu asetik asit, metal asetatların kuru damıtılmasıyla hazırlandı. On altıncı yüzyılda Alman simyacı Andreas Libavius böyle bir prosedürü tanımladı ve bu yöntemle üretilen buzlu asetik asidi sirke ile karşılaştırdı. Sirkede suyun varlığı asetik asitin özellikleri üzerinde çok büyük bir etkiye sahiptir. Yüzyıllar boyunca birçok kimyager buzul asetik asit ve sirke içinde bulunan asidin iki farklı madde olduğuna inanırlardı. Fransız kimyacı Pierre Adet, onların aynı olduğunu kanıtladı.
1847'de, Alman kimyacı Hermann Kolbe ilk kez inorganik materyallerden asetik asit sentezlemiştir. Bu reaksiyon dizisi karbon disülfidden karbon tetraklorüre klorinasyonu, ardından tetrakloretilene ve sulu klorinasyona trikloroasetik aside kadar pirolizden oluşmaktaydı ve asetik aside elektrolitik indirgeme ile sonlandırıldı.
1910'a gelindiğinde, çoğu buzlu asetik asit, odunun damıtılmasından "pirolitik likör" den elde edildi. Asetik asit bundan sonra kireç sütü ile muamele edilerek izole edilmiş ve sonuçta meydana gelen kalsiyum asetat asetik asidi geri kazanmak için sülfürik asit ile asitleştirilmiştir. Bu sırada Almanya, yaklaşık% 30'u indigo boya üretimi için kullanılan 10.000 tonluk glasiyal asetik asit üretiyordu. [2] [3]
BIOKIMYA
Asetik asitten türetilen asetil grubu, neredeyse tüm yaşam formlarının biyokimyası için temeldir. Koenzim A'ya bağlandığında, karbonhidrat ve yağ metabolizmasının merkezi olur. Bununla birlikte, hücrelerde serbest asetik asitin konsantrasyonu, hücre içeriğinin pH'ının kontrolünü bozmaktan kaçınmak için düşük bir seviyede tutulur. Bazı uzun zincirli karboksilik asitlerin (yağ asitleri) aksine, doğal trigliseritlerde asetik asit oluşmaz. Bununla birlikte, yapay trigliserit triasetin (gliserin triasetat) yaygın bir gıda katkısıdır ve kozmetikte ve topikal ilaçlarda bulunur.
Asetik asit, bazı bakteriler, özellikle de Acetobacter cinsi ve Clostridium acetobutylicum tarafından üretilir ve dışarı atılır. Bu bakteriler genel olarak gıda maddelerinde, suda ve toprakta bulunurlar ve asetik asit, meyveler ve diğer bazı gıdalar bozulduğunda doğal olarak üretilir. Asetik asit aynı zamanda insanlarda ve diğer primatların vajinal yağlanmasının bir bileşeni olup, hafif bir antibakteriyel ajan olarak hizmet ettiği görülmektedir. [7]
Asetik asit, bazı bakteriler, özellikle de Acetobacter cinsi ve Clostridium acetobutylicum tarafından üretilir ve dışarı atılır. Bu bakteriler genel olarak gıda maddelerinde, suda ve toprakta bulunurlar ve asetik asit, meyveler ve diğer bazı gıdalar bozulduğunda doğal olarak üretilir. Asetik asit aynı zamanda insanlarda ve diğer primatların vajinal yağlanmasının bir bileşeni olup, hafif bir antibakteriyel ajan olarak hizmet ettiği görülmektedir. [7]
ÜRETİM
Asetik asit hem sentetik hem de bakteriyel fermantasyon ile üretilir. Bugün, biyolojik rota dünya üretiminin sadece yüzde 10'unu oluşturuyor, ancak dünyadaki gıda saflık yasalarının çoğu gıdalarda kullanılan sirkenin biyolojik kökenli olmasını şart koştuğu için, sirke üretimi için önemini koruyor. Kimyasal endüstrisinde kullanılmak üzere üretilen asetik asitin yaklaşık yüzde 75'i, aşağıda açıklanmış olan metanol karbonilasyon ile yapılmıştır. Alternatif yöntemler diğerlerini açıklar. [8]
Dünya çapında toplam bakire asetik asit üretimi yaklaşık olarak Amerika Birleşik Devletleri'nde yaklaşık olarak yarısı üretilen 5 Mt / a (yılda milyon metrik ton) olarak tahmin edilmektedir. Avrupa üretimi yaklaşık 1 Mt / a seviyesinde ve düşüş gösteriyor ve Japonya'da 0.7 Mt / a üretiliyor. Her yıl 1,5 Mt daha geri dönüştürülmekte ve dünya piyasasını 6,5 Mt / a seviyesine çıkarmaktadır. [9] En büyük iki asetik asit üreticisi Celanese ve BP Chemicals'dır. Diğer önemli üreticiler arasında Millennium Chemicals, Sterling Chemicals, Samsung, Eastman ve Svensk Etanolkemi bulunuyor.
Metanol karbonilasyon
En bakir asetik asit, metanol karbonilasyon ile üretilir. Bu işlemde, metanol ve karbon monoksit kimyasal denkleme göre asetik asit üretmek için reaksiyona girer:
CH3OH + CO → CH3COOH
İşlem, bir ara ürün olarak iyodometanı içerir ve üç aşamada gerçekleşir. Karbonilasyon için genellikle bir metal kompleksi olan bir katalizöre ihtiyaç vardır (aşama 2). (1) CH3OH + HI → CH3I + H2O (2) CH3I + CO → CH3COI (3) CH3COI + H2O → CH3COOH + HI Proses koşullarını değiştirerek aynı bitki üzerinde asetik anhidrit de üretilebilir. Hem metanol hem de karbon monoksit emtia hammaddesi olduğundan, metanol karbonilasyonu uzun zamandır asetik asit üretimi için çekici bir yöntem olarak ortaya çıkmıştır. İngiliz Celanese'deki Henry Drefyus, 1925 yılına kadar bir metanol karbonilasyon pilot tesisi geliştirdi. [10] Ancak, ihtiyaç duyulan yüksek basınçlarda (200 atm veya daha fazla) korozif reaksiyon karışımını içerebilecek pratik malzeme eksikliği, bu yolların bir süredir ticarileştirilmesini engellemiştir. Bir kobalt katalizörü kullanılan ilk ticari metanol karbonilasyon işlemi, 1963 yılında Alman kimya şirketi BASF tarafından geliştirilmiştir. 1968'de, verimli bir şekilde çalışabilen rodyum bazlı bir katalizör (cis- [Rh (CO) 2I2] -) keşfedilmiştir. neredeyse hiç yan ürün içermeyen daha düşük basınç. Bu katalizörü kullanan ilk bitki, 1970 yılında ABD kimya şirketi Monsanto tarafından imal edildi ve rodyum katalizeli metanol karbonilasyonu, asetik asit üretiminin baskın yöntemi haline geldi (Monsanto prosesine bakınız). 1990'ların sonlarında, kimya şirketi BP Chemicals, rutenyum tarafından teşvik edilen Cativa katalizörünü ([Ir (CO) 2I2] -) ticarileştirdi. Bu iridyum katalizli süreç daha yeşil ve daha verimli [11] ve çoğunlukla aynı üretim tesislerinde Monsanto sürecini büyük ölçüde tamamlamıştır.
Asetaldehit oksidasyonu
Monsanto işleminin ticarileştirilmesinden önce asetik asit, asetaldehitin oksidasyonuyla üretildi. Bu, metanol karbonilasyonu ile rekabetsiz olmasına rağmen, ikinci en önemli üretim yöntemi olmaya devam etmektedir. Asetaldehit, bütan veya hafif naftanın oksidasyonu veya etilenin hidratlanması yoluyla üretilebilir. Bütan veya hafif nafta, manganez, kobalt ve kromun da dahil olduğu çeşitli metal iyonlarının varlığında hava ile ısıtıldığında, peroksitler oluşur ve daha sonra kimyasal denkleme göre asetik asit üretmek üzere ayrışırlar.
Bütan veya hafif nafta, manganez, kobalt ve kromun da dahil olduğu çeşitli metal iyonlarının varlığında hava ile ısıtıldığında, peroksitler oluşur ve daha sonra kimyasal denkleme göre asetik asit üretmek üzere ayrışırlar.
2 C4H10 + 5 O2 → 4 CH3COOH + 2 H2O
Tipik olarak, reaksiyon, bütanı bir sıvı hâlâ muhafaza ederken mümkün olduğunca sıcak olacak şekilde tasarlanmış bir sıcaklık ve basınç kombinasyonunda gerçekleştirilir. Tipik reaksiyon koşulları 150 ° C ve 55 atm'dir. Butanon, etil asetat, formik asit ve propionik asit dahil olmak üzere birçok yan ürün de oluşabilir. Bu yan ürünler de ticari olarak değerlidir ve eğer bu ekonomik olarak faydalı ise daha fazla üretmek için reaksiyon koşulları değiştirilebilir. Bununla birlikte, asetik asidin bu yan ürünlerden ayrılması, işlemin maliyetine katkıda bulunur.
Benzer koşullar altında ve bütan oksidasyonu için kullanılan benzer katalizörleri kullanarak, asetaldehit, asetik asit üretmek için havadaki oksijen tarafından oksitlenebilir.
2 CH3CHO + O2 → 2 CH3COOH
Modern katalizörleri kullanarak, bu reaksiyon% 95'ten daha büyük bir asetik asit verimine sahip olabilir. Ana yan ürünler etil asetat, formik asit ve formaldehittir, hepsi asetik asitten daha düşük kaynama noktasına sahiptir ve damıtma ile kolayca ayrılır.
ETİLEN OKSİDASYONU
FERMENTASYON
Oksidatif fermantasyon
İnsanlık tarihinin çoğu için, asetik asit, sirke şeklinde, Acetobacter cinsinden bakteriler tarafından yapılmıştır. Yeterli oksijen verildiğinde, bu bakteriler çeşitli alkollü yiyeceklerden sirke üretebilir. Yaygın olarak kullanılan yemler arasında elma şarabı, şarap ve mayalanmış tahıl, malt, pirinç veya patates ezmesi bulunur. Bu bakteriler tarafından kolaylaştırılan genel kimyasal reaksiyon
C2H5OH + O2 → CH3COOH + H2O
Asetamacter ile aşılanmış ve sıcak, havadar bir yerde tutulan bir seyreltik alkol çözeltisi, birkaç ay boyunca sirke haline gelecektir. Endüstriyel sirke yapım yöntemleri, bakteriye oksijen tedariki geliştirerek bu süreci hızlandırır.
Fermantasyon ile üretilen ilk sirke yığınları, muhtemelen şarap yapım sürecindeki hataları takip etti. Eğer çok yüksek bir sıcaklıkta fermente edilmesi gerekiyorsa, asetobakter, doğal olarak üzümlerde meydana gelen mayayı ezecektir. Mutfak, tıbbi ve sıhhi amaçlar için sirke talebi arttıkça, şarap üreticileri üzümleri olgunlaşmadan ve şaraba hazır hale gelmeden önce sıcak yaz aylarında sirke üretmek için diğer organik malzemeleri kullanmayı çabucak öğrendi. Bununla birlikte, bu yöntem yavaştı, ve hakemler süreci anlamadığı için her zaman başarılı olmadı.
İlk modern ticari süreçlerden biri, ilk olarak 1823'te Almanya'da uygulanan "hızlı yöntem" veya "Alman yöntemi" idi. Bu süreçte fermantasyon, odun talaşı veya odun kömürü ile dolu bir kulede gerçekleşiyor. Alkol içeren yem, kulenin tepesine ve tabanda doğal veya zorlanmış konveksiyonla sağlanan taze havaya damlatılır. Bu işlemde geliştirilmiş hava kaynağı, sirkeyi aylardan haftalara hazırlamak için zamanı kısaltmıştır.
Bugün sirkenin çoğu, 1949 yılında Otto Hromatka ve Heinrich Ebner tarafından tanımlanan, batık tank kültüründe yapılmıştır. Bu yöntemde, alkol sürekli olarak karıştırılmış bir tankta sirke ile fermente edilir ve solüsyondan hava kabarcıklanarak oksijen sağlanır. Bu yöntemi kullanarak, yüzde 15 asetik asit sirkesi sadece iki ila üç gün içinde hazırlanabilir.
Anaerobik fermantasyon
Clostridium cinsinin birkaç üyesi de dahil olmak üzere bazı anaerobik bakteri türleri, ara ürün olarak etanol kullanmadan doğrudan şekerleri asetik aside dönüştürebilir. Bu bakteriler tarafından yürütülen genel kimyasal reaksiyon şu şekilde temsil edilebilir:
C6H12O6 → 3 CH3COOH
Bir endüstriyel kimyacının bakış açısından daha ilginç olarak, bu asetojenik bakterilerin çoğu, metanol, karbon monoksit veya karbon dioksit ve hidrojen karışımı gibi tek karbonlu bileşiklerden asetik asit üretebilir:
2 CO2 + 4 H2 → CH3COOH + 2 H2O
Clostridium'ın şekerleri doğrudan kullanma veya daha az maliyetli girdilerden asetik asit üretme yeteneği, bu bakterilerin asetik asidi potansiyel olarak Acetobacter gibi etanol-oksidizörlerden daha verimli üretebileceği anlamına gelir. Bununla birlikte, Clostridium bakterileri, Acetobacter'den daha az asit toleranslıdır. En asit toleranslı Clostridium suşları bile yüzde 20'ye kadar asetik asit sirkesi üretebilen bazı Asetobacter suşlarına kıyasla, sadece yüzde birkaç asetik asit sirkesi üretebilir. Şu anda, Clostridium kullanarak üretmek ve daha sonra konsantre etmek yerine, Acetobacter kullanarak sirke üretmek için daha uygun maliyetli kalır. Sonuç olarak, 1940'dan beri asetojenik bakteriler bilinmesine rağmen, endüstriyel kullanımları birkaç niş uygulama ile sınırlı kalmaktadır.
UYGULAMALAR
Asetik asit, birçok kimyasal bileşiğin üretimi için kimyasal bir reaktiftir. En büyük tek asetik asit kullanımı, vinil asetat monomeri üretimindedir, bunu takiben asetik anhidrit ve ester üretimi takip eder. Sirke kullanılan asetik asit hacmi nispeten küçüktür.
DİĞER UYGULAMALAR
Asetik asitlerin seyreltilmiş çözeltileri de hafif asitliği için kullanılır. Ev ortamındaki örnekler arasında, fotografik filmlerin geliştirilmesi sırasında bir durdurma banyosunda kullanımı ve kireç çözücü maddelerde musluk ve su ısıtıcılarmdan kireç pulunu çıkarmak bulunmaktadır. Asitlik ayrıca, denizanasının batma hücrelerini devre dışı bırakarak, hemen uygulandığı takdirde ciddi yaralanmayı veya ölümü önleyerek ve Vosol gibi müstahzarlardaki insanlarda dış kulak enfeksiyonlarını tedavi etmek için kutu denizanası sokmasının işlenmesinde kullanılır. Eşdeğer olarak, asetik asit, bakteri ve mantar gelişimini engellemek için canlı hayvan silajı için püskürtmeli bir koruyucu olarak kullanılır.
Buzlu asetik asit de bir siğil ve verruca çıkarıcı olarak kullanılır. Siğilin etrafındaki deriye yayılmasını önlemek için bir halka pellum yağı uygulanır ve siğil veya verrukaya bir veya iki damla buzlu asetik asit uygulanır. Tedavi günlük olarak tekrarlanır. Bu yöntem ağrısızdır ve diğer birçok tedavinin aksine yüksek bir başarı oranına sahiptir. Buzlu asetik asitin emilmesi küçük miktarlarda güvenlidir.
Aşağıdakileri içeren asetik asitten birkaç organik veya inorganik tuz üretilir:
• Sodyum asetat - tekstil endüstrisinde ve gıda koruyucu olarak kullanılır (E262).
• Bakır (II) asetat - bir pigment ve bir fungisit olarak kullanılır.
• Alüminyum asetat ve demir (II) asetat - boyalar için mordan olarak kullanılır.
• Palladium (II) asetat - Heck reaksiyonu gibi organik bağlanma reaksiyonları için bir katalizör olarak kullanılır.
Üretilen ikame edilmiş asetik asitler şunları içerir:
• Monokloroasetik asit (MCA), dikloroasetik asit (bir yan ürün olarak kabul edilir) ve trikloroasetik asit. MCA, indigo boya üretiminde kullanılır.
• Reaktif etil bromoasetat üretmek için esterlenen Bromoasetik asit.
• Organik sentezde ortak bir reaktif olan trifloroasetik asit.
Bu diğer uygulamalarda (TPA dışında) kullanılan asetik asit miktarları, dünya çapında asetik asit kullanımının yüzde 5-10'unu oluşturmaktadır. Bununla birlikte, bu uygulamaların TPA üretimi kadar büyümemesi beklenmemektedir.
Emniyet
Konsantre asetik asit aşındırıcıdır ve bu nedenle cilt yanıkları, kalıcı göz hasarı ve mukoza zarında tahrişe neden olabileceğinden uygun bakım ile kullanılmalıdır. Bu yanıklar veya kabarcıklar, maruziyetten birkaç saat sonra ortaya çıkmayabilir. Lateks eldivenler koruma sağlamaz, bu yüzden bileşiği kullanırken nitril kauçuktan yapılmış eldivenler gibi özel olarak dayanıklı eldivenler giyilmelidir. Konsantre asetik asit, laboratuvarda bazı zorluklarla ateşlenebilir. Ortam sıcaklığı 39 ° C'yi (102 ° F) aşarsa yanıcı bir risk haline gelir ve bu sıcaklığın üzerinde hava ile patlayıcı karışımlar oluşturabilir (patlayıcı limitler:% 5.4-16).
Asetik asit çözeltilerinin tehlikeleri konsantrasyona bağlıdır.
ACETIC ACID
Overview
Description
Product Information
Applications
Physicochemical Information
Toxicological Information
Safety Information according to GHS
Safety Information
Storage and Shipping Information
Transport Information
Specifications
Key Spec Table
Pricing & Availability
Key Spec Table
CAS # EC Number Hill Formula Chemical Formula Molar Mass
64-19-7 200-580-7 C₂H₄O₂ CH₃COOH 60.05 g/mol
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Description
Catalogue Number 818755
Synonyms Ethanoic acid
Product Information
CAS number 64-19-7
EC index number 607-002-00-6
EC number 200-580-7
Hill Formula C₂H₄O₂
Chemical formula CH₃COOH
Molar Mass 60.05 g/mol
HS Code 2915 21 00
Structure formula Image Structure formula Image
Quality Level MQ200
Applications
Application Acetic acid 99-100% for synthesis. CAS No. 64-19-7, EC Number 200-580-7.
Physicochemical Information
Boiling point 116 - 118 °C (1013 hPa)
Density 1.05 g/cm3 (20 °C)
Explosion limit 4 - 19.9 %(V)
Flash point 40 °C
Ignition temperature 485 °C
Melting Point 17 °C
pH value 2.5 (50 g/l, H₂O, 20 °C)
Vapor pressure 15.4 hPa (20 °C)
Viscosity kinematic 1.17 mm2/s (20 °C)
Solubility 602.9 g/l soluble
Acetic Acid is a synthetic carboxylic acid with antibacterial and antifungal properties. Although its mechanism of action is not fully known, undissociated acetic acid may enhance lipid solubility allowing increased fatty acid accumulation on the cell membrane or in other cell wall structures. Acetic acid, as a weak acid, can inhibit carbohydrate metabolism resulting in subsequent death of the organism.
NCI Thesaurus (NCIt)
Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical that is used in the production of plastic soft drink bottles, photographic film; and polyvinyl acetate for wood glue, as well as many synthetic fibres and fabrics. In households diluted acetic acid is often used as a cleaning agent. In the food industry acetic acid is used as an acidity regulator. The acetyl group, derived from acetic acid, is fundamental to the biochemistry of virtually all forms of life. When bound to coenzyme A it is central to the metabolism of carbohydrates and fats. However, the concentration of free acetic acid in cells is kept at a low level to avoid disrupting the control of the pH of the cell contents. Acetic acid is produced and excreted by certain bacteria, notably the Acetobacter genus and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and acetic acid is produced naturally as fruits and some other foods spoil. Acetic acid is also a component of the vaginal lubrication of humans and other primates, where it appears to serve as a mild antibacterial agent. Acetic acid is found to be associated with phenylketonuria, which is an inborn error of metabolism.
Human Metabolome Database (HMDB)
Acetic acid is a simple monocarboxylic acid containing two carbons. It has a role as a protic solvent, a food acidity regulator, an antimicrobial food preservative and a Daphnia magna metabolite. It is a conjugate acid of an acetate.
Acetic acid /əˈsiːtɪk/, systematically named ethanoic acid /ˌɛθəˈnoʊɪk/, is a colourless liquid organic compound with the chemical formula CH3COOH (also written as CH3CO2H, C2H4O2, or HC2H3O2). When undiluted, it is sometimes called glacial acetic acid. Vinegar is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. Acetic acid has a distinctive sour taste and pungent smell. In addition to household vinegar, it is mainly produced as a precursor to polyvinyl acetate and cellulose acetate. It is classified as a weak acid since it only partially dissociates in solution, but concentrated acetic acid is corrosive and can attack the skin.
Acetic acid is the second simplest carboxylic acid (after formic acid). It consists of a methyl group attached to a carboxyl group. It is an important chemical reagent and industrial chemical, used primarily in the production of cellulose acetate for photographic film, polyvinyl acetate for wood glue, and synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry, acetic acid is controlled by the food additive code E260 as an acidity regulator and as a condiment. In biochemistry, the acetyl group, derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats.
The global demand for acetic acid is about 6.5 million metric tons per year (Mt/a), of which approximately 1.5 Mt/a is met by recycling; the remainder is manufactured from methanol.[9] Vinegar is mostly dilute acetic acid, often produced by fermentation and subsequent oxidation of ethanol.
Contents
1 Nomenclature
2 Properties
2.1 Acidity
2.2 Structure
2.3 Solvent properties
2.4 Biochemistry
3 Production
3.1 Methanol carbonylation
3.2 Acetaldehyde oxidation
3.3 Ethylene oxidation
3.4 Oxidative fermentation
3.5 Anaerobic fermentation
4 Uses
4.1 Vinyl acetate monomer
4.2 Ester production
4.3 Acetic anhydride
4.4 Use as solvent
4.5 Medical use
4.6 Foods
5 Reactions
5.1 Organic chemistry
5.2 Reactions with inorganic compounds
5.3 Other derivatives
6 History
6.1 Interstellar medium
7 Health effects and safety
8 See also
9 References
10 External links
Nomenclature
The trivial name acetic acid is the most commonly used and preferred IUPAC name. The systematic name ethanoic acid, a valid IUPAC name, is constructed according to the substitutive nomenclature.[10] The name acetic acid derives from acetum, the Latin word for vinegar, and is related to the word acid itself.
Glacial acetic acid is a name for water-free (anhydrous) acetic acid. Similar to the German name Eisessig (ice vinegar), the name comes from the ice-like crystals that form slightly below room temperature at 16.6 °C (61.9 °F) (the presence of 0.1% water lowers its melting point by 0.2 °C).[11]
A common symbol for acetic acid is AcOH, where Ac is the pseudoelement symbol representing the acetyl group CH
3-C(=O)-; the conjugate base, acetate (CH
3COO-), is thus represented as AcO-.[12] (The Ac is not to be confused with the symbol for the element actinium; the context prevents confusion among organic chemists). To better reflect its structure, acetic acid is often written as CH
3-C(O)OH, CH
3-C(=O)OH, CH
3COOH, and CH
3CO
2H. In the context of acid-base reactions, the abbreviation HAc is sometimes used,[13] where Ac in this case is a symbol for acetate (rather than acetyl). Acetate is the ion resulting from loss of H+
from acetic acid. The name acetate can also refer to a salt containing this anion, or an ester of acetic acid.[14]
Properties
Acetic acid crystals
Acidity
The hydrogen centre in the carboxyl group (-COOH) in carboxylic acids such as acetic acid can separate from the molecule by ionization:
CH3COOH ⇌ CH3CO2- + H+
Because of this release of the proton (H+), acetic acid has acidic character. Acetic acid is a weak monoprotic acid. In aqueous solution, it has a pKa value of 4.76.[15] Its conjugate base is acetate (CH3COO-). A 1.0 M solution (about the concentration of domestic vinegar) has a pH of 2.4, indicating that merely 0.4% of the acetic acid molecules are dissociated.[16] However, in very dilute (< 10-6 M) solution acetic acid is >90% dissociated.
Deprotonation equilibrium of acetic acid in water
Cyclic dimer of acetic acid; dashed green lines represent hydrogen bonds
Structure
In solid acetic acid, the molecules form chains, individual molecules being interconnected by hydrogen bonds.[17] In the vapour at 120 °C (248 °F), dimers can be detected. Dimers also occur in the liquid phase in dilute solutions in non-hydrogen-bonding solvents, and a certain extent in pure acetic acid,[18] but are disrupted by hydrogen-bonding solvents. The dissociation enthalpy of the dimer is estimated at 65.0-66.0 kJ/mol, and the dissociation entropy at 154-157 J mol-1 K-1.[19] Other carboxylic acids engage in similar intermolecular hydrogen bonding interactions.[20]
Solvent properties
Liquid acetic acid is a hydrophilic (polar) protic solvent, similar to ethanol and water. With a moderate relative static permittivity (dielectric constant) of 6.2, it dissolves not only polar compounds such as inorganic salts and sugars, but also non-polar compounds such as oils as well as polar solutes. It is miscible with polar and non-polar solvents such as water, chloroform, and hexane. With higher alkanes (starting with octane), acetic acid is not miscible at all compositions, and solubility of acetic acid in alkanes declines with longer n-alkanes.[21] The solvent and miscibility properties of acetic acid make it a useful industrial chemical, for example, as a solvent in the production of dimethyl terephthalate.[9]
Biochemistry
At physiological pHs, acetic acid is usually fully ionised to acetate.
The acetyl group, formally derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats. Unlike longer-chain carboxylic acids (the fatty acids), acetic acid does not occur in natural triglycerides. However, the artificial triglyceride triacetin (glycerine triacetate) is a common food additive and is found in cosmetics and topical medicines.[22]
Acetic acid is produced and excreted by acetic acid bacteria, notably the genus Acetobacter and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and acetic acid is produced naturally as fruits and other foods spoil. Acetic acid is also a component of the vaginal lubrication of humans and other primates, where it appears to serve as a mild antibacterial agent.[23]
Production
Purification and concentration plant for acetic acid in 1884
Acetic acid is produced industrially both synthetically and by bacterial fermentation. About 75% of acetic acid made for use in the chemical industry is made by the carbonylation of methanol, explained below.[9] The biological route accounts for only about 10% of world production, but it remains important for the production of vinegar because many food purity laws require vinegar used in foods to be of biological origin. Other processes are methyl formate isomerization, conversion of syngas to acetic acid, and gas phase oxidation of ethylene and ethanol.[24] Acetic acid is often a side product of different reactions, i.e. during heterogeneous catalytic acrylic acid synthesis[25][26][27] or fermentative lactic acid production.[28] As of 2003-2005, total worldwide production of virgin acetic acid[29] was estimated at 5 Mt/a (million tonnes per year), approximately half of which was produced in the United States. European production was approximately 1 Mt/a and declining, while Japanese production was 0.7 Mt/a. Another 1.5 Mt were recycled each year, bringing the total world market to 6.5 Mt/a.[30][31] Since then the global production has increased to 10.7 Mt/a (in 2010), and further; however, a slowing in this increase in production is predicted.[32] The two biggest producers of virgin acetic acid are Celanese and BP Chemicals. Other major producers include Millennium Chemicals, Sterling Chemicals, Samsung, Eastman, and Svensk Etanolkemi.[33]
Methanol carbonylation
Most acetic acid is produced by methanol carbonylation. In this process, methanol and carbon monoxide react to produce acetic acid according to the equation:
Methanol formylation.png
The process involves iodomethane as an intermediate, and occurs in three steps. A catalyst, metal carbonyl, is needed for the carbonylation (step 2).[34]
CH3OH + HI → CH3I + H2O
CH3I + CO → CH3COI
CH3COI + H2O → CH3COOH + HI
Two related processes for the carbonylation of methanol: the rhodium-catalyzed Monsanto process, and the iridium-catalyzed Cativa process. The latter process is greener and more efficient[35] and has largely supplanted the former process, often in the same production plants. Catalytic amounts of water are used in both processes, but the Cativa process requires less, so the water-gas shift reaction is suppressed, and fewer by-products are formed.
By altering the process conditions, acetic anhydride may also be produced on the same plant using the rhodium catalysts.[36]
Acetaldehyde oxidation
Prior to the commercialization of the Monsanto process, most acetic acid was produced by oxidation of acetaldehyde. This remains the second-most-important manufacturing method, although it is usually not competitive with the carbonylation of methanol. The acetaldehyde can be produced by hydration of acetylene. This was the dominant technology in the early 1900s.[37]
Light naphtha components are readily oxidized by oxygen or even air to give peroxides, which decompose to produce acetic acid according to the chemical equation, illustrated with butane:
2 C4H10 + 5 O2 → 4 CH3CO2H + 2 H2O
Such oxidations require metal catalyst, such as the naphthenate salts of manganese, cobalt, and chromium.
The typical reaction is conducted at temperatures and pressures designed to be as hot as possible while still keeping the butane a liquid. Typical reaction conditions are 150 °C (302 °F) and 55 atm.[38] Side-products may also form, including butanone, ethyl acetate, formic acid, and propionic acid. These side-products are also commercially valuable, and the reaction conditions may be altered to produce more of them where needed. However, the separation of acetic acid from these by-products adds to the cost of the process.[39]
Under similar conditions and using similar catalysts as are used for butane oxidation, the oxygen in air to produce acetic acid can oxidize acetaldehyde.[39]
2 CH3CHO + O2 → 2 CH3CO2H
Using modern catalysts, this reaction can have an acetic acid yield greater than 95%. The major side-products are ethyl acetate, formic acid, and formaldehyde, all of which have lower boiling points than acetic acid and are readily separated by distillation.[39]
Ethylene oxidation
Acetaldehyde may be prepared from ethylene via the Wacker process, and then oxidised as above.
In more recent times, chemical company Showa Denko, which opened an ethylene oxidation plant in Ōita, Japan, in 1997, commercialised a cheaper single-stage conversion of ethylene to acetic acid.[40] The process is catalyzed by a palladium metal catalyst supported on a heteropoly acid such as silicotungstic acid. Similar process use the same metal catalyst on silicotungstic acid and silica:[41]
C2H4 + O2 → CH3CO2H
It is thought to be competitive with methanol carbonylation for smaller plants (100-250 kt/a), depending on the local price of ethylene. The approach will be based on utilizing a novel selective photocatalytic oxidation technology for the selective oxidation of ethylene and ethane to acetic acid. Unlike traditional oxidation catalysts, the selective oxidation process will use UV light to produce acetic acid at ambient temperatures and pressure.
Oxidative fermentation
For most of human history, acetic acid bacteria of the genus Acetobacter have made acetic acid, in the form of vinegar. Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes. The overall chemical reaction facilitated by these bacteria is:
C2H5OH + O2 → CH3COOH + H2O
A dilute alcohol solution inoculated with Acetobacter and kept in a warm, airy place will become vinegar over the course of a few months. Industrial vinegar-making methods accelerate this process by improving the supply of oxygen to the bacteria.[42]
The first batches of vinegar produced by fermentation probably followed errors in the winemaking process. If must is fermented at too high a temperature, acetobacter will overwhelm the yeast naturally occurring on the grapes. As the demand for vinegar for culinary, medical, and sanitary purposes increased, vintners quickly learned to use other organic materials to produce vinegar in the hot summer months before the grapes were ripe and ready for processing into wine. This method was slow, however, and not always successful, as the vintners did not understand the process.[43]
One of the first modern commercial processes was the "fast method" or "German method", first practised in Germany in 1823. In this process, fermentation takes place in a tower packed with wood shavings or charcoal. The alcohol-containing feed is trickled into the top of the tower, and fresh air supplied from the bottom by either natural or forced convection. The improved air supply in this process cut the time to prepare vinegar from months to weeks.[44]
Nowadays, most vinegar is made in submerged tank culture, first described in 1949 by Otto Hromatka and Heinrich Ebner.[45] In this method, alcohol is fermented to vinegar in a continuously stirred tank, and oxygen is supplied by bubbling air through the solution. Using modern applications of this method, vinegar of 15% acetic acid can be prepared in only 24 hours in batch process, even 20% in 60-hour fed-batch process.[43]
Anaerobic fermentation
Species of anaerobic bacteria, including members of the genus Clostridium or Acetobacterium can convert sugars to acetic acid directly without creating ethanol as an intermediate. The overall chemical reaction conducted by these bacteria may be represented as:
C6H12O6 → 3 CH3COOH
These acetogenic bacteria produce acetic acid from one-carbon compounds, including methanol, carbon monoxide, or a mixture of carbon dioxide and hydrogen:
2 CO2 + 4 H2 → CH3COOH + 2 H2O
This ability of Clostridium to metabolize sugars directly, or to produce acetic acid from less costly inputs, suggests that these bacteria could produce acetic acid more efficiently than ethanol-oxidizers like Acetobacter. However, Clostridium bacteria are less acid-tolerant than Acetobacter. Even the most acid-tolerant Clostridium strains can produce vinegar in concentrations of only a few per cent, compared to Acetobacter strains that can produce vinegar in concentrations up to 20%. At present, it remains more cost-effective to produce vinegar using Acetobacter, rather than using Clostridium and concentrating it. As a result, although acetogenic bacteria have been known since 1940, their industrial use is confined to a few niche applications.[46]
Uses
Acetic acid is a chemical reagent for the production of chemical compounds. The largest single use of acetic acid is in the production of vinyl acetate monomer, closely followed by acetic anhydride and ester production. The volume of acetic acid used in vinegar is comparatively small.[9][31]
Vinyl acetate monomer
The primary use of acetic acid is the production of vinyl acetate monomer (VAM). In 2008, this application was estimated to consume a third of the world's production of acetic acid.[9] The reaction consists of ethylene and acetic acid with oxygen over a palladium catalyst, conducted in the gas phase.[47]
2 H3C-COOH + 2 C2H4 + O2 → 2 H3C-CO-O-CH=CH2 + 2 H2O
Vinyl acetate can be polymerised to polyvinyl acetate or other polymers, which are components in paints and adhesives.[47]
Ester production
The major esters of acetic acid are commonly used as solvents for inks, paints and coatings. The esters include ethyl acetate, n-butyl acetate, isobutyl acetate, and propyl acetate. They are typically produced by catalyzed reaction from acetic acid and the corresponding alcohol:
H3C-COOH + HO-R → H3C-CO-O-R + H2O, (R = a general alkyl group)
Most acetate esters, however, are produced from acetaldehyde using the Tishchenko reaction. In addition, ether acetates are used as solvents for nitrocellulose, acrylic lacquers, varnish removers, and wood stains. First, glycol monoethers are produced from ethylene oxide or propylene oxide with alcohol, which are then esterified with acetic acid. The three major products are ethylene glycol monoethyl ether acetate (EEA), ethylene glycol monobutyl ether acetate (EBA), and propylene glycol monomethyl ether acetate (PMA, more commonly known as PGMEA in semiconductor manufacturing processes, where it is used as a resist solvent). This application consumes about 15% to 20% of worldwide acetic acid. Ether acetates, for example EEA, have been shown to be harmful to human reproduction.[31]
Acetic anhydride
The product of the condensation of two molecules of acetic acid is acetic anhydride. The worldwide production of acetic anhydride is a major application, and uses approximately 25% to 30% of the global production of acetic acid. The main process involves dehydration of acetic acid to give ketene at 700-750 °C. Ketene is thereafter reacted with acetic acid to obtain the anhydride:[48]
CH3CO2H → CH2=C=O + H2O
CH3CO2H + CH2=C=O → (CH3CO)2O
Acetic anhydride is an acetylation agent. As such, its major application is for cellulose acetate, a synthetic textile also used for photographic film. Acetic anhydride is also a reagent for the production of heroin and other compounds.[48]
Use as solvent
Glacial acetic acid is an excellent polar protic solvent, as noted above. It is frequently used as a solvent for recrystallization to purify organic compounds. Acetic acid is used as a solvent in the production of terephthalic acid (TPA), the raw material for polyethylene terephthalate (PET). In 2006, about 20% of acetic acid was used for TPA production.[31]
Acetic acid is often used as a solvent for reactions involving carbocations, such as Friedel-Crafts alkylation. For example, one stage in the commercial manufacture of synthetic camphor involves a Wagner-Meerwein rearrangement of camphene to isobornyl acetate; here acetic acid acts both as a solvent and as a nucleophile to trap the rearranged carbocation.[49]
Glacial acetic acid is used in analytical chemistry for the estimation of weakly alkaline substances such as organic amides. Glacial acetic acid is a much weaker base than water, so the amide behaves as a strong base in this medium. It then can be titrated using a solution in glacial acetic acid of a very strong acid, such as perchloric acid.[50]
Medical use
Main article: Acetic acid (medical use)
Acetic acid injection into a tumor has been used to treat cancer since the 1800s.[51][52]
Acetic acid is used as part of cervical cancer screening in many areas in the developing world.[53] The acid is applied to the cervix and if an area of white appears after about a minute the test is positive.[53]
Acetic acid is an effective antiseptic when used as a 1% solution, with broad spectrum of activity against streptococci, staphylococci, pseudomonas, enterococci and others.[54][55][56] It may be used to treat skin infections caused by pseudomonas strains resistant to typical antibiotics.[57]
While diluted acetic acid is used in iontophoresis, no high quality evidence supports this treatment for rotator cuff disease.[58][59]
As a treatment for otitis externa, it is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.[60]
Foods
Main article: Vinegar
Acetic acid has 349 kcal per 100 g.[61] Vinegar is typically no less than 4% acetic acid by mass.[62][63][64] Legal limits on acetic acid content vary by jurisdiction. Vinegar is used directly as a condiment, and in the pickling of vegetables and other foods. Table vinegar tends to be more diluted (4% to 8% acetic acid), while commercial food pickling employs solutions that are more concentrated. The proportion of acetic acid used worldwide as vinegar is not as large as commercial uses, but is by far the oldest and best-known application.[65]
Reactions
Organic chemistry
acetyl chloride
Acetyl chloride.svg
SOCl2
Leftward reaction arrow
acetic acid
Acetic acid Structural Formula V1.svg
(i) LiAlH4, ether
Rightward reaction arrow
(ii) H
3O+
ethanol
Ethanol Skelett.svg
Two typical organic reactions of acetic acid
Acetic acid undergoes the typical chemical reactions of a carboxylic acid. Upon treatment with a standard base, it converts to metal acetate and water. With strong bases (e.g., organolithium reagents), it can be doubly deprotonated to give LiCH2CO2Li. Reduction of acetic acid gives ethanol. The OH group is the main site of reaction, as illustrated by the conversion of acetic acid to acetyl chloride. Other substitution derivatives include acetic anhydride; this anhydride is produced by loss of water from two molecules of acetic acid. Esters of acetic acid can likewise be formed via Fischer esterification, and amides can be formed. When heated above 440 °C (824 °F), acetic acid decomposes to produce carbon dioxide and methane, or to produce ketene and water:[66][67][68]
CH3COOH → CH4 + CO2
CH3COOH → CH2CO + H2O
Reactions with inorganic compounds
Acetic acid is mildly corrosive to metals including iron, magnesium, and zinc, forming hydrogen gas and salts called acetates:
Mg + 2 CH3COOH → (CH3COO)2Mg + H2
Because aluminium forms a passivating acid-resistant film of aluminium oxide, aluminium tanks are used to transport acetic acid. Metal acetates can also be prepared from acetic acid and an appropriate base, as in the popular "baking soda + vinegar" reaction:
NaHCO3 + CH3COOH → CH3COONa + CO2 + H2O
A colour reaction for salts of acetic acid is iron(III) chloride solution, which results in a deeply red colour that disappears after acidification.[69] A more sensitive test uses lanthanum nitrate with iodine and ammonia to give a blue solution.[70] Acetates when heated with arsenic trioxide form cacodyl oxide, which can be detected by its malodorous vapours.[71]
Other derivatives
Organic or inorganic salts are produced from acetic acid. Some commercially significant derivatives:
Sodium acetate, used in the textile industry and as a food preservative (E262).
Copper(II) acetate, used as a pigment and a fungicide.
Aluminium acetate and iron(II) acetate-used as mordants for dyes.
Palladium(II) acetate, used as a catalyst for organic coupling reactions such as the Heck reaction.
Halogenated acetic acids are produced from acetic acid. Some commercially significant derivatives:
Chloroacetic acid (monochloroacetic acid, MCA), dichloroacetic acid (considered a by-product), and trichloroacetic acid. MCA is used in the manufacture of indigo dye.
Bromoacetic acid, which is esterified to produce the reagent ethyl bromoacetate.
Trifluoroacetic acid, which is a common reagent in organic synthesis.
Amounts of acetic acid used in these other applications together account for another 5-10% of acetic acid use worldwide.[31]
History
Vinegar was known early in civilization as the natural result of exposure of beer and wine to air, because acetic acid-producing bacteria are present globally. The use of acetic acid in alchemy extends into the 3rd century BC, when the Greek philosopher Theophrastus described how vinegar acted on metals to produce pigments useful in art, including white lead (lead carbonate) and verdigris, a green mixture of copper salts including copper(II) acetate. Ancient Romans boiled soured wine to produce a highly sweet syrup called sapa. Sapa that was produced in lead pots was rich in lead acetate, a sweet substance also called sugar of lead or sugar of Saturn, which contributed to lead poisoning among the Roman aristocracy.[72]
In the 16th-century German alchemist Andreas Libavius described the production of acetone from the dry distillation of lead acetate, ketonic decarboxylation. The presence of water in vinegar has such a profound effect on acetic acid's properties that for centuries chemists believed that glacial acetic acid and the acid found in vinegar were two different substances. French chemist Pierre Adet proved them identical.[72][73]
glass beaker of crystallised acetic acid
Crystallised acetic acid.
In 1845 German chemist Hermann Kolbe synthesised acetic acid from inorganic compounds for the first time. This reaction sequence consisted of chlorination of carbon disulfide to carbon tetrachloride, followed by pyrolysis to tetrachloroethylene and aqueous chlorination to trichloroacetic acid, and concluded with electrolytic reduction to acetic acid.[74]
By 1910, most glacial acetic acid was obtained from the pyroligneous liquor, a product of the distillation of wood. The acetic acid was isolated by treatment with milk of lime, and the resulting calcium acetate was then acidified with sulfuric acid to recover acetic acid. At that time, Germany was producing 10,000 tons of glacial acetic acid, around 30% of which was used for the manufacture of indigo dye.[72][75]
Because both methanol and carbon monoxide are commodity raw materials, methanol carbonylation long appeared to be attractive precursors to acetic acid. Henri Dreyfus at British Celanese developed a methanol carbonylation pilot plant as early as 1925.[76] However, a lack of practical materials that could contain the corrosive reaction mixture at the high pressures needed (200 atm or more) discouraged commercialization of these routes. The first commercial methanol carbonylation process, which used a cobalt catalyst, was developed by German chemical company BASF in 1963. In 1968, a rhodium-based catalyst (cis-[Rh(CO)2I2]-) was discovered that could operate efficiently at lower pressure with almost no by-products. US chemical company Monsanto Company built the first plant using this catalyst in 1970, and rhodium-catalyzed methanol carbonylation became the dominant method of acetic acid production (see Monsanto process). In the late 1990s, the chemicals company BP Chemicals commercialised the Cativa catalyst ([Ir(CO)2I2]-), which is promoted by iridium[77] for greater efficiency. This iridium-catalyzed Cativa process is greener and more efficient[35] and has largely supplanted the Monsanto process, often in the same production plants.
Interstellar medium
Interstellar acetic acid was discovered in 1996 by a team led by David Mehringer[78] using the former Berkeley-Illinois-Maryland Association array at the Hat Creek Radio Observatory and the former Millimeter Array located at the Owens Valley Radio Observatory. It was first detected in the Sagittarius B2 North molecular cloud (also known as the Sgr B2 Large Molecule Heimat source). Acetic acid has the distinction of being the first molecule discovered in the interstellar medium using solely radio interferometers; in all previous ISM molecular discoveries made in the millimetre and centimetre wavelength regimes, single dish radio telescopes were at least partly responsible for the detections.[78]
Health effects and safety
Concentrated acetic acid is corrosive to skin.[79][80] These burns or blisters may not appear until hours after exposure.
Prolonged inhalation exposure (eight hours) to acetic acid vapours at 10 ppm can produce some irritation of eyes, nose, and throat; at 100 ppm marked lung irritation and possible damage to lungs, eyes, and skin may result. Vapour concentrations of 1,000 ppm cause marked irritation of eyes, nose and upper respiratory tract and cannot be tolerated. These predictions were based on animal experiments and industrial exposure.
In 12 workers exposed for two or more years to acetic acid airborne average concentration of 51 ppm (estimated), produced symptoms of conjunctive irritation, upper respiratory tract irritation, and hyperkeratotic dermatitis. Exposure to 50 ppm or more is intolerable to most persons and results in intensive lacrimation and irritation of the eyes, nose, and throat, with pharyngeal oedema and chronic bronchitis. Unacclimatised humans experience extreme eye and nasal irritation at concentrations in excess of 25 ppm, and conjunctivitis from concentrations below 10 ppm has been reported. In a study of five workers exposed for seven to 12 years to concentrations of 80 to 200 ppm at peaks, the principal findings were blackening and hyperkeratosis of the skin of the hands, conjunctivitis (but no corneal damage), bronchitis and pharyngitis, and erosion of the exposed teeth (incisors and canines).[81]
The hazards of solutions of acetic acid depend on the concentration. The following table lists the EU classification of acetic acid solutions:[82]
Concentration
by weight Molarity Classification R-Phrases
10-25% 1.67-4.16 mol/L Irritant (Xi) R36/38
25-90% 4.16-14.99 mol/L Corrosive (C) R34
>90% >14.99 mol/L Corrosive (C) Flammable (F) R10, R35
Concentrated acetic acid can be ignited only with difficulty at standard temperature and pressure, but becomes a flammable risk in temperatures greater than 39 °C (102 °F), and can form explosive mixtures with air at higher temperatures (explosive limits: 5.4-16%).
Acetic acid, systematically named ethanoic acid, is a colourless liquid organic compound with the chemical formula CH3COOH (also written as CH3CO2H or C2H4O2). When undiluted, it is sometimes called glacial acetic acid. Vinegar is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. Acetic acid has a distinctive sour taste and pungent smell. In addition to household vinegar, it is mainly produced as a precursor to polyvinyl acetate and cellulose acetate. It is classified as a weak acid since it only partially dissociates in solution, but concentrated acetic acid is corrosive and can attack the skin.
Acetic acid is the second simplest carboxylic acid (after formic acid). It consists of a methyl group attached to a carboxyl group. It is an important chemical reagent and industrial chemical, used primarily in the production of cellulose acetate for photographic film, polyvinyl acetate for wood glue, and synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry, acetic acid is controlled by the food additive code E260 as an acidity regulator and as a condiment. In biochemistry, the acetyl group, derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats.
The global demand for acetic acid is about 6.5 million metric tons per year (Mt/a), of which approximately 1.5 Mt/a is met by recycling; the remainder is manufactured from methanol. Vinegar is mostly dilute acetic acid, often produced by fermentation and subsequent oxidation of ethanol.
Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical that is used in the production of plastic soft drink bottles, photographic film; and polyvinyl acetate for wood glue, as well as many synthetic fibres and fabrics. In households diluted acetic acid is often used as a cleaning agent. In the food industry acetic acid is used as an acidity regulator. The acetyl group, derived from acetic acid, is fundamental to the biochemistry of virtually all forms of life. When bound to coenzyme A it is central to the metabolism of carbohydrates and fats. However, the concentration of free acetic acid in cells is kept at a low level to avoid disrupting the control of the pH of the cell contents. Acetic acid is produced and excreted by certain bacteria, notably the Acetobacter genus and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and acetic acid is produced naturally as fruits and some other foods spoil. Acetic acid is also a component of the vaginal lubrication of humans and other primates, where it appears to serve as a mild antibacterial agent. Acetic acid is found to be associated with phenylketonuria, which is an inborn error of metabolism.
Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. It is one of the simplest carboxylic acids (the second-simplest, after formic acid) and has the chemical formula CH3COOH. In its pure, water-free state, called glacial acetic acid, it is a colorless, hygroscopic liquid that freezes below 16.7°C (62°F) to a colorless crystalline solid. It is corrosive, and its vapor irritates the eyes, produces a burning sensation in the nose, and can lead to a sore throat and lung congestion. The term acetate is used when referring to the carboxylate anion (CH3COO-) or any of the salts or esters of acetic acid.
This acid is an important chemical reagent and industrial chemical useful for the production of various synthetic fibers and other polymeric materials. These polymers include polyethylene terephthalate, used mainly in soft drink bottles; cellulose acetate, used mainly for photographic film; and polyvinyl acetate, for wood glue. In households, diluted acetic acid is often used in descaling agents. The food industry uses it (under the food additive code E260) as an acidity regulator.
NOMENCLATURE
The trivial name acetic acid is the most commonly used and officially preferred name by the International Union of Pure and Applied Chemistry (IUPAC). This name derives from acetum, the Latin word for vinegar. The synonym ethanoic acid is a systematic name that is sometimes used in introductions to chemical nomenclature.
Glacial acetic acid is a trivial name for water-free acetic acid. Similar to the German name Eisessig (literally, ice-vinegar), the name comes from the ice-like crystals that form slightly below room temperature at 16.7°C (about 62°F).
The most common and official abbreviation for acetic acid is AcOH or HOAc where Acstands for the acetyl group CH3-C(=O)-;. In the context of acid-base reactions the abbreviation HAc is often used where Acinstead stands for the acetate anion(CH3COO-), although this use is regarded by many as misleading. In either case, the Ac is not to be confused with the abbreviation for the chemical element actinium.
Acetic acid has the empirical formula CH2O and the molecular formula C2H4O2. The latter is often written as CH3-COOH, CH3COOH, or CH3CO2H to better reflect its structure. The ion resulting from loss of H+ from acetic acid is the acetate anion. The name acetate can also refer to a salt containing this anion or an ester of acetic acid.
HISTORY
Vinegar is as old as civilization itself, perhaps older. Acetic acid-producing bacteria are present throughout the world, and any culture practicing the brewing of beer or wine inevitably discovered vinegar as the natural result of these alcoholic beverages being exposed to air.
The use of acetic acid in chemistry extends into antiquity. In the third century B.C.E., Greek philosopher Theophrastos described how vinegar acted on metals to produce pigments useful in art, including white lead(lead carbonate) and verdigris, a green mixture of copper salts including copper(II) acetate. Ancient Romans boiled soured wine in lead pots to produce a highly sweet syrup called sapa. Sapa was rich in lead acetate, a sweet substance also called sugar of lead or sugar of Saturn, which contributed to lead poisoning among the Roman aristocracy. The eighth-century Persian alchemist Jabir Ibn Hayyan (Geber) concentrated acetic acid from vinegar through distillation.
In the Renaissance, glacial acetic acid was prepared through the dry distillation of metal acetates. The sixteenth-century German alchemist Andreas Libavius described such a procedure, and he compared the glacial acetic acid produced by this means to vinegar. The presence of water in vinegar has such a profound effect on acetic acid's properties that for centuries many chemists believed that glacial acetic acid and the acid found in vinegar were two different substances. The French chemist Pierre Adet proved them to be identical.
In 1847, the German chemist Hermann Kolbe synthesized acetic acid from inorganic materials for the first time. This reaction sequence consisted of chlorination of carbon disulfide to carbon tetrachloride, followed by pyrolysis to tetrachloroethylene and aqueous chlorination to trichloroacetic acid, and concluded with electrolytic reduction to acetic acid.
By 1910, most glacial acetic acid was obtained from the "pyroligneous liquor" from distillation of wood. The acetic acid was isolated from this by treatment with milk of lime, and the resultant calcium acetate was then acidified with sulfuric acid to recover acetic acid. At this time Germany was producing 10,000 tons of glacial acetic acid, around 30 percent of which was used for the manufacture of indigo dye.[2][3]
BIOCHEMISTRY
The acetyl group, derived from acetic acid, is fundamental to the biochemistry of virtually all forms of life. When bound to coenzyme A it is central to the metabolism of carbohydrates and fats. However, the concentration of free acetic acid in cells is kept at a low level to avoid disrupting the control of the pH of the cell contents. Unlike some longer-chain carboxylic acids (the fatty acids), acetic acid does not occur in natural triglycerides. However, the artificial triglyceride triacetin (glycerin triacetate) is a common food additive, and is found in cosmetics and topical medicines.
Acetic acid is produced and excreted by certain bacteria, notably the Acetobacter genus and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and acetic acid is produced naturally as fruits and some other foods spoil. Acetic acid is also a component of the vaginal lubrication of humans and other primates, where it appears to serve as a mild antibacterial agent.[7]
PRODUCTION
Acetic acid is produced both synthetically and by bacterial fermentation. Today, the biological route accounts for only about 10 percent of world production, but it remains important for vinegar production, as many of the world food purity laws stipulate that vinegar used in foods must be of biological origin. About 75 percent of acetic acid made for use in the chemical industry is made by methanol carbonylation, explained below. Alternative methods account for the rest.[8]
Total worldwide production of virgin acetic acid is estimated at 5 Mt/a (million metric tons per year), approximately half of which is produced in the United States. European production stands at approximately 1 Mt/a and is declining, and 0.7 Mt/a is produced in Japan. Another 1.5 Mt are recycled each year, bringing the total world market to 6.5 Mt/a.[9] The two biggest producers of virgin acetic acid are Celanese and BP Chemicals. Other major producers include Millennium Chemicals, Sterling Chemicals, Samsung, Eastman, and Svensk Etanolkemi.
Methanol carbonylation
Most virgin acetic acid is produced by methanol carbonylation. In this process, methanol and carbon monoxide react to produce acetic acid according to the chemical equation:
CH3OH + CO → CH3COOH
The process involves iodomethane as an intermediate, and occurs in three steps. A catalyst, usually a metal complex, is needed for the carbonylation (step 2).
(1) CH3OH + HI → CH3I + H2O
(2) CH3I + CO → CH3COI
(3) CH3COI + H2O → CH3COOH + HI
By altering the process conditions, acetic anhydride may also be produced on the same plant. Because both methanol and carbon monoxide are commodity raw materials, methanol carbonylation long appeared to be an attractive method for acetic acid production. Henry Drefyus at British Celanese developed a methanol carbonylation pilot plant as early as 1925.[10] However, a lack of practical materials that could contain the corrosive reaction mixture at the high pressures needed (200 atm or more) discouraged commercialisation of these routes for some time. The first commercial methanol carbonylation process, which used a cobalt catalyst, was developed by German chemical company BASF in 1963. In 1968, a rhodium-based catalyst (cis-[Rh(CO)2I2]-) was discovered that could operate efficiently at lower pressure with almost no by-products. The first plant using this catalyst was built by U.S. chemical company Monsanto in 1970, and rhodium-catalysed methanol carbonylation became the dominant method of acetic acid production (see Monsanto process). In the late 1990s, the chemicals company BP Chemicals commercialised the Cativa catalyst ([Ir(CO)2I2]-), which is promoted by ruthenium. This iridium-catalysed process is greener and more efficient[11] and has largely supplanted the Monsanto process, often in the same production plants.
Acetaldehyde oxidation
Prior to the commercialisation of the Monsanto process, most acetic acid was produced by oxidation of acetaldehyde. This remains the second most important manufacturing method, although it is uncompetitive with methanol carbonylation. The acetaldehyde may be produced via oxidation of butane or light naphtha, or by hydration of ethylene.
When butane or light naphtha is heated with air in the presence of various metal ions, including those of manganese, cobalt and chromium, peroxides form and then decompose to produce acetic acid according to the chemical equation
2 C4H10 + 5 O2 → 4 CH3COOH + 2 H2O
Typically, the reaction is run at a combination of temperature and pressure designed to be as hot as possible while still keeping the butane a liquid. Typical reaction conditions are 150 °C and 55 atm. Several side products may also form, including butanone, ethyl acetate, formic acid, and propionic acid. These side products are also commercially valuable, and the reaction conditions may be altered to produce more of them if this is economically useful. However, the separation of acetic acid from these by-products adds to the cost of the process.
Under similar conditions and using similar catalysts as are used for butane oxidation, acetaldehyde can be oxidised by the oxygen in airto produce acetic acid
2 CH3CHO + O2 → 2 CH3COOH
Using modern catalysts, this reaction can have an acetic acid yield greater than 95%. The major side products are ethyl acetate, formic acid, and formaldehyde, all of which have lower boiling points than acetic acid and are readily separated by distillation.
ETHYLNE OXIDATION
FERMENTATION
Oxidative fermentation
For most of human history, acetic acid, in the form of vinegar, has been made by bacteria of the genus Acetobacter. Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes. The overall chemical reaction facilitated by these bacteria is
C2H5OH + O2 → CH3COOH + H2O
A dilute alcohol solution inoculated with Acetobacter and kept in a warm, airy place will become vinegar over the course of a few months. Industrial vinegar-making methods accelerate this process by improving the supply of oxygen to the bacteria.
The first batches of vinegar produced by fermentation probably followed errors in the winemaking process. If must is fermented at too high a temperature, acetobacter will overwhelm the yeast naturally occurring on the grapes. As the demand for vinegar for culinary, medical, and sanitary purposes increased, vintners quickly learned to use other organic materials to produce vinegar in the hot summer months before the grapes were ripe and ready for processing into wine. This method was slow, however, and not always successful, as the vintners did not understand the process.
One of the first modern commercial processes was the "fast method" or "German method," first practised in Germany in 1823. In this process, fermentation takes place in a tower packed with wood shavings or charcoal. The alcohol-containing feed is trickled into the top of the tower, and fresh air supplied from the bottom by either natural or forced convection. The improved air supply in this process cut the time to prepare vinegar from months to weeks.
Most vinegar today is made in submerged tank culture, first described in 1949 by Otto Hromatka and Heinrich Ebner. In this method, alcohol is fermented to vinegar in a continuously stirred tank, and oxygen is supplied by bubbling air through the solution. Using this method, vinegar of 15 percent acetic acid can be prepared in only two to three days.
Anaerobic fermentation
Some species of anaerobic bacteria, including several members of the genus Clostridium, can convert sugars to acetic acid directly, without using ethanol as an intermediate. The overall chemical reaction conducted by these bacteria may be represented as:
C6H12O6 → 3 CH3COOH
More interestingly from the point of view of an industrial chemist, many of these acetogenic bacteria can produce acetic acid from one-carbon compounds, including methanol, carbon monoxide, or a mixture of carbon dioxide and hydrogen:
2 CO2 + 4 H2 → CH3COOH + 2 H2O
This ability of Clostridium to utilise sugars directly, or to produce acetic acid from less costly inputs, means that these bacteria could potentially produce acetic acid more efficiently than ethanol-oxidisers like Acetobacter. However, Clostridium bacteria are less acid-tolerant than Acetobacter. Even the most acid-tolerant Clostridium strains can produce vinegar of only a few per cent acetic acid, compared to some Acetobacter strains that can produce vinegar of up to 20 percent acetic acid. At present, it remains more cost-effective to produce vinegar using Acetobacter than to produce it using Clostridium and then concentrating it. As a result, although acetogenic bacteria have been known since 1940, their industrial use remains confined to a few niche applications.
APPLICATIONS
Acetic acid is a chemical reagent for the production of many chemical compounds. The largest single use of acetic acid is in the production of vinyl acetate monomer, closely followed by acetic anhydride and ester production. The volume of acetic acid used in vinegar is comparatively small.
OTHER APPLICATIONS
Dilute solutions of acetic acids are also used for their mild acidity. Examples in the household environment include the use in a stop bath during the development of photographic films, and in descaling agents to remove limescale from taps and kettles. The acidity is also used for treating the sting of the box jellyfish by disabling the stinging cells of the jellyfish, preventing serious injury or death if applied immediately, and for treating outer ear infections in people in preparations such as Vosol. Equivalently, acetic acid is used as a spray-on preservative for livestock silage, to discourage bacterial and fungal growth.
Glacial acetic acid is also used as a wart and verruca remover. A ring of petroleum jelly is applied to the skin around the wart to prevent spread, and one to two drops of glacial acetic acid are applied to the wart or verruca. Treatment is repeated daily. This method is painless and has a high success rate, unlike many other treatments. Absorption of glacial acetic acid is safe in small amounts.
Several organic or inorganic salts are produced from acetic acid, including:
• Sodium acetate-used in the textile industry and as a food preservative (E262).
• Copper(II) acetate-used as a pigment and a fungicide.
• Aluminium acetate and iron(II) acetate-used as mordants for dyes.
• Palladium(II) acetate-used as a catalyst for organic coupling reactions such as the Heck reaction.
Substituted acetic acids produced include:
• Monochloroacetic acid (MCA), dichloroacetic acid (considered a by-product), and trichloroacetic acid. MCA is used in the manufacture of indigo dye.
• Bromoacetic acid, which is esterified to produce the reagent ethyl bromoacetate.
• Trifluoroacetic acid, which is a common reagent in organic synthesis.
Amounts of acetic acid used in these other applications together (apart from TPA) account for another 5-10 percent of acetic acid use worldwide. These applications are, however, not expected to grow as much as TPA production.
SAFETY
Concentrated acetic acid is corrosive and must therefore be handled with appropriate care, since it can cause skin burns, permanent eye damage, and irritation to the mucous membranes. These burns or blisters may not appear until several hours after exposure. Latex gloves offer no protection, so specially resistant gloves, such as those made of nitrile rubber, should be worn when handling the compound. Concentrated acetic acid can be ignited with some difficulty in the laboratory. It becomes a flammable risk if the ambient temperature exceeds 39 °C (102 °F), and can form explosive mixtures with air above this temperature (explosive limits: 5.4-16 percent).
The hazards of solutions of acetic acid depend on the concentration.
Acide acétique
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Page d'aide sur l'homonymie « Acétique » redirige ici. Pour l'article homophone, voir Ascétique.
Acide acétique
Formule développée de l'acide acétique Représentation 3D de l'acide acétique
Formule topologique et représentation 3D de l'acide acétique
Identification
Nom UICPA acide acétique
Nom systématique acide éthanoïque
Synonymes
acide acétique glacial
acide éthylique, acide méthanecarboxylique
No CAS 64-19-7
No ECHA 100.000.528
No CE 200-580-7
No RTECS AF1225000
Code ATC G01AD02 S02AA10
DrugBank DB03166
PubChem 176
ChEBI 15366
No E E260
FEMA 2006
SMILES
[Afficher]
InChI
[Afficher]
Apparence liquide incolore, d'odeur âcre et fortement vinaigrée1.
Propriétés chimiques
Formule brute C2H4O2 [Isomères]
Masse molaire5 60,052 ± 0,0025 g/mol
C 40 %, H 6,71 %, O 53,29 %,
pKa 4,76 à 25 °C2
Moment dipolaire 1,70 ± 0,03 D3
Diamètre moléculaire 0,442 nm4
Propriétés physiques
T° fusion 16,64 °C6
T° ébullition 117,9 °C6
Solubilité Miscible avec l'eau, l'acétone, l'alcool, le benzène, le glycérol, l'éther, le tétrachlorure de carbone; Pratiquement insol. dans le disulfure de carbone2
Totalement miscible à l'hexane, au toluène.
Paramètre de solubilité δ 20,7 MPa1/2 (25 °C)7;
18,9 J1/2·cm-3/2 (25 °C)4;
12,4 cal1/2·cm-3/28
Masse volumique 1,0492 g·cm-3 (liquide,20 °C)6
[+]
T° d'auto-inflammation 465 °C10
Point d'éclair 39 °C (coupelle fermée)1
Limites d'explosivité dans l'air 5,4-16 %vol1
Pression de vapeur saturante 1,5 kPa à 20 °C1
[+]
Viscosité dynamique 1,22 mPa·s à 25 °C
Point critique 4,53 MPa à 319,56 °C10
Thermochimie
S0gaz, 1 bar 282,848 J·mol-1·K-111
S0liquide, 1 bar 158,0 J·mol-1·K-111
ΔfH0gaz -433 kJ·mol-111
ΔfH0liquide -483,52 kJ·mol-111
ΔfusH° 11,728 kJ·mol-1 à 16,75 °C11
ΔvapH° 23,7 kJ·mol-1 à 117,95 °C11
Cp 123,1 J·mol-1·K-1 (liquide,25 °C)
63,44 J·mol-1·K-1 (gaz,25 °C)11
[+]
PCS 874,2 kJ·mol-113 (liquide)
PCI -875,16 kJ·mol-111
Propriétés électroniques
1re énergie d'ionisation 10,65 ± 0,02 eV (gaz)14
Cristallographie
Classe cristalline ou groupe d'espace Pna21 15
Volume 297,27 Å315
Propriétés optiques
Indice de réfraction {\displaystyle n_{D}^{20}}n^{ 20 }_{ D } 1,37206
Précautions
SGH16,17
SGH02 : InflammableSGH05 : Corrosif
Danger
H226, H314, P280, P305, P310, P338, P351,
[+]
SIMDUT18
B3 : Liquide combustibleE : Matière corrosive
B3, E,
[+]
NFPA 704
Symbole NFPA 704
230
Transport
83
2789
[+]
80
2790
[+]
Écotoxicologie
DL50 3,31 g·kg-1 (rat, oral)
525 mg·kg-1 (souris, i.v.)19
LogP -0,311
Seuil de l'odorat bas : 0,03 ppm
haut : 0,15 ppm20
Composés apparentés
Isomère(s) Glycolaldéhyde
Autres composés
Anhydride acétique
Unités du SI et CNTP, sauf indication contraire.
modifier Consultez la documentation du modèle
L'acide acétique ou acide éthanoïque est un acide carboxylique avec une chaîne carbonée théorique en C2, analogue à l'éthane, de masse molaire 60 g/mol et de formule chimique brute C2H4O2 ou semi-développée CH3-CO-OH. L'adjectif du nom courant provient du latin acetum, signifiant vinaigre. En effet, l'acide acétique représente le principal constituant du vinaigre après l'eau, puisqu'il lui donne son goût acide et son odeur piquante détectable à partir d'1 ppm22.
La distillation du vinaigre, attestée dès l'époque médiévale en Europe, a permis d'obtenir l'acide acétique pur, liquide combustible incolore à forte odeur de vinaigre, de masse volumique de l'ordre d'1,05 g·cm-3 à 20 °C qui se solidifie par simple immersion dans un bain eau-glace23. Il est encore connu sous le nom d'acide acétique glacial ou autrefois de vinaigre fort. C'est le premier acide industriel connu.
Ce liquide très faiblement conducteur, incolore, inflammable et hygroscopique représente à température ambiante un des plus simples acides monocarboxyliques, avec l'acide formique. Son acidité caractérisée en solution aqueuse par un pKa = 4,76 vient de sa capacité à perdre temporairement le proton de sa fonction carboxylique, le transformant ainsi en ion acétate CH3COO-. C'est un acide faible.
Cet acide coagule le latex et a des propriétés bactériostatiques, ce qui permet de l'utiliser comme désinfectant. Il est également utilisé comme composant d'insecticides et d'agent de nettoyage pour la fabrication de semi-conducteurs22. Il est corrosif et ses vapeurs sont irritantes pour le nez et les yeux.
Très corrosif vis-à-vis des tissus organiques et vivants, il doit être manipulé avec soin. Bien qu'il n'ait pas été jugé cancérogène ou dangereux pour l'environnement, il peut causer des brûlures ainsi que des dommages permanents à la bouche, au nez, à la gorge et aux poumons. À certaines doses et en co-exposition chronique avec un produit cancérogène, son caractère irritant en fait un promoteur tumoral de tumeurs (bénignes et malignes)22. Ceci a été démontré expérimentalement chez le rat22.
Dans le corps humain, l'acide acétique est normalement produit après la consommation d'alcool : l'éthanol est converti en acétaldéhyde qui est alors converti en acide acétique sous l'influence de l'enzyme acétaldéhyde déshydrogénase et ensuite en acetyl-coA par la ligase acétate-CoA.
Production
La demande mondiale d'acide acétique est d'environ 6,5 millions de tonnes par an (Mt/a). Industriellement, il est produit par l'oxydation en phase liquide du n-butane, ou il est récupéré dans la production d'acétate de cellulose ou d'alcool polyvinylique.
Usages
C'est un réactif très utilisé dans l'industrie ou les laboratoires notamment :
comme solvant : miscible à l'eau et à divers solvants organiques tels l'éthanol, l'éther diéthylique, le glycérol22 mais insoluble dans le disulfure de carbone22, c'est aussi un bon solvant des gommes, résines, du phosphore, du soufre et d'acides halogénohydriques22 ? ;
dans la production d'anhydride acétique, acétate de cellulose, d'acétate de vinyle monomère, et d'autres acétates, ainsi que de médicaments, pesticides, colorants, la fabrication de produits photographiques22 ;
dans l'alimentation (production de vinaigres de fruit22...), additif alimentaire ;
les textiles22 ;
comme agent de nettoyage (de semi-conducteurs22) ;
coagulant (du latex naturel22) ;
bactériostatique (en solution22) ;
dans la fabrication de plastiques tels le polytéréphtalate d'éthylène (PET) ou l'acétate de cellulose, utile à la production d'acétate de vinyle (peintures, adhésifs) et de solvants organiques ;
comme additif dans les produits dérivés du tabac (arôme).
mordançage lors de colorations de coupes histologiques (ex : coloration au carmino-vert)
processus d'hydrolyse24, de condensation24 et/ou de gélification pour la fabrication de catalyseur ou lors du procédé sol-gel25
antibactérien et acidification gastrique dans l'élevage notamment porcin26.
Nomenclature
Le nom trivial ancien, acide acétique, dérive d'acetum, mot latin qui désigne le vinaigre ou aceti-vinum. Il est encore le plus utilisé dans l'espace francophone et anglophone mais l'IUPAC a normalisé le terme acide éthanoïque, à la place de l'ancien nom chimique français acide éthylique. Plus tolérant que la nomenclature IUPAC en 1960, les Chemical Abstracts ont conservé néanmoins les noms courants pour les deux premiers acides carboxyliques en C1 et C2, soit l'acide formique et l'acide acétique.
Acide acétique glacial reste aussi un nom trivial qui désigne communément l'acide acétique pur au laboratoire. Similaire au nom allemand « Eisessig » (littéralement : vinaigre glacé), ce nom s'explique par les cristaux d'acide acétique semblables à de la glace qui se forment à une température légèrement inférieure à la température ambiante (à moins de 17 °C, température de fusion de l'acide acétique pur).
L'abréviation la plus courante pour l'acide acétique est AcOH ou HOAc, Ac désignant le groupe fonctionnel acétyle CH3-CO-.
La formule brute de l'acide acétique est C2H4O2. On l'écrit également souvent CH3COOH ou CH3CO2H afin de mieux traduire sa structure. L'ion résultant de la perte du proton H+ porte le nom d'acétate. Acétate peut également faire référence à un sel contenant cet anion ou à un ester de l'acide acétique.
Historique
Acide acétique cristallisé
Le vinaigre fort est connu en Mésopotamie il y a plus de 3 000 ans av. J.-C.27. Les bactéries acétiques produisant l'acide acétique à partir du vin et d'oxygène ont été décrites par le chimiste Louis Pasteur. Elles sont présentes partout dans le monde civilisé, et toute culture pratiquant le brassage de la bière ou du vin a inévitablement découvert le vinaigre, résultat naturel de l'évolution de ces boissons alcoolisées laissées à l'air libre.
L'usage de l'acide acétique en chimie remonte à l'Antiquité. Au iiie siècle av. J.-C., le philosophe grec Théophraste décrit comment le vinaigre agit sur le métal et produit ainsi des pigments utiles pour l'art, incluant le plomb blanc (carbonate de plomb) et vert-de-gris, un mélange vert de sels de cuivre incluant l'acétate de cuivre II (tous produits toxiques). Les anciens Romains faisaient bouillir le « vin aigre » dans des récipients de plomb pour produire un sirop très sucré appelé sapa. Le sapa était riche en acétate de plomb, une substance sucrée appelée sucre de plomb ou sucre de Saturne, et qui provoqua de nombreux empoisonnements au plomb dans l'aristocratie romaine, la maladie correspondant à une intoxication aiguë ou chronique par le plomb est notamment nommée saturnisme. L'alchimiste perse Jabir Ibn Hayyan (Geber) concentra l'acide acétique à partir du vinaigre par distillation[réf. nécessaire].
Durant la Renaissance, l'acide acétique « glacial » était préparé par distillation sèche d'acétates de métal. Au xvie siècle, l'alchimiste allemand Andreas Libavius en décrivit la procédure, et compara l'acide pur ainsi produit au vinaigre. La présence d'eau dans le vinaigre a tant d'influence sur les propriétés de l'acide acétique que pendant des siècles de nombreux chimistes ont cru que l'acide acétique glacial et l'acide présent dans le vinaigre étaient deux substances différentes. C'est le chimiste français Pierre Auguste Adet qui prouva qu'ils étaient le même composé chimique.
En 1847, le chimiste allemand Hermann Kolbe synthétisa l'acide acétique à partir de matières inorganiques pour la première fois. La séquence de cette réaction consistait en la chloration de disulfure de carbone en tétrachlorométhane, suivie d'une pyrolyse en tétrachloroéthylène, puis d'une chloration aqueuse en acide trichloroacétique, et enfin conclure par une réduction par électrolyse pour obtenir l'acide acétique28.
Vers 1910, la majorité de l'acide acétique glacial était obtenue à partir de la « liqueur pyroligneuse » issue de la distillation du bois27. L'acide acétique était isolé grâce à un traitement à l'hydroxyde de calcium, et l'acétate de calcium ainsi obtenu était alors acidifié par un ajout d'acide sulfurique pour reformer l'acide acétique. L'Allemagne en produisait à l'époque 10 000 tonnes par an, dont 30 % était utilisé pour la production de colorant indigo29,30.