| Sodium dodecylbenzenesulfonate | |
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sodium dodecylbenzenesulfonate |
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Other names
dodecylbenzenesulfonic acid, sodium salt; LAS; linear alkylbenzene sulfonate |
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| Identifiers | |
| CAS number | 25155-30-0 |
| Properties | |
| Molecular formula | C18H29NaO3S |
| Molar mass | 348.48 g/mol |
| Solubility in water | 20% |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Sodium dodecylbenzenesulfonate 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.[1]
Contents |
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 to the right 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 (see figure to left) but are not as widely used because they biodegrade too slowly.
Further complicating the description of the commercial materials, sodium dodecylbenzenesulfonate is but 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. Given the large scale of the application, the 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.[1]
The salt has an LD50 of 2.3 mg/liter for fish, about 4x more toxic than the branched tetrapropylenebenzenesulfonate. It is however biodegraded more rapidly. Oxidative degradation initiates at the alkyl chain.[1]