Sodium dodecylbenzenesulfonate

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Sodium dodecylbenzenesulfonate
Natriumdodecylbenzolsulfonat.svg
Identifiers
CAS number 25155-30-0 N
PubChem 23667983
Jmol-3D images Image 1
Properties
Molecular formula C18H29NaO3S
Molar mass 348.48 g mol−1
Solubility in water 20%
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 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]

Alkylbenzenesulfonates[edit]

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.

Production[edit]

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.[1]

Environmental considerations[edit]

Biodegradability has been well studied,[3] and is affected by the isomerization (branching). 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[edit]

  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.
  3. ^ Zhang, C.; Valsaraj, K. T.; Constant, W. D.; Roy, D. (1999). "Aerobic biodegradation kinetics of four anionic and nonionic surfactants at sub- and supra-critical micelle concentrations (CMCs)". Water Research 33: 115. doi:10.1016/S0043-1354(98)00170-5.  edit