Sodium dodecylbenzenesulfonate (linear alkylbenzene sulfonate or LAS) is a series of organic compounds with the formula C12H25C6H4SO3Na. It is a colourless salt with useful properties as a surfactant. It is usually produced as a mixture of related sulfonates. It is a major component of laundry detergent.Most sodium dodecylbenzenesulfonates are a member of the linear alkylbenzenesulfonates, meaning that the dodecyl group (C12H25) is unbranched. This dodecyl chain is attached at the 4-position of the benzenesulfonate group. Linear dodecyl-4-benzenesulfonate anions can exist in six isomers (ignoring optical isomers), depending on the carbon of the dodecyl group that is attached to the benzene ring. The isomer shown below left is 4-(5-dodecyl)benzenesulfonate (4 indicating the position of the benzene ring, 5 indicating the position on the dodecane chain). Branched isomers, e.g. those derived from tetramerized propylene, are also known (below right) but are not as widely used because they biodegrade too slowly.Further complicating the description of the commercial materials, sodium dodecylbenzenesulfonate is one component of a mixture of compounds that feature variable alkyl chain lengths aside from C12, mainly ranging from C10-C16. Dodecylbenzenesulfonate is considered representative of the entire class of compounds, since the mean number of alkyl carbon atoms in the alkylbenzenesulfonates is 12. Billions of kilograms are produced annually. Alkylbenzenesulfonates have been prepared by many methods.[2] In the most common route, benzene is alkylated by long chain monoalkenes (e.g. dodecene) using hydrogen fluoride as a catalyst. The purified dodecylbenzenes (and related derivatives) are then sulfonated with sulfur trioxide to give the sulfonic acid. The sulfonic acid is subsequently neutralized with sodium hydroxide.
