Sodium dodecylbenzenesulfonate

Sodium dodecylbenzenesulfonate
IUPAC name sodium dodecylbenzenesulfonate
Other names dodecylbenzenesulfonic acid, sodium salt, labs
Identifiers
CAS number	[http://www.commonchemistry.org/ChemicalDetail.aspx?ref=25155-30-0, [68081-81-2 (mixture mainly C10-C16), 68411- 30-3 (mixture mainly C10-C13) 25155-30-0, [68081-81-2 (mixture mainly C10-C16), 68411- 30-3 (mixture mainly C10-C13)] Y
Properties
Molecular formula	C18H29NaO3S
Molar mass	348.48 g/mol
Solubility in water	20%
Y dodecylbenzenesulfonate (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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]

Alkylbenzenesulfonates

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.

A branched dodecylbenzenesulfonate, which has been phased out in developed countries.

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.

Production

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]

Environmental considerations

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]

References

1. ^ ^{a b c} Kurt Kosswig,"Surfactants" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, 2005, Weinheim. doi:10.1002/14356007.a25_747
2. ^ "5th World Conference on Detergents" Arno Cahn, ed., 2003. ISBN 1-893997-40-5.