α-Olefin sulfonate
Class of chemical compounds
From Wikipedia, the free encyclopedia
α-Olefin sulfonates (also: alpha-olefin sulfonates or AOS) are a group of anionic surfactants, which are used as detergents.[1] The compounds contain a - mostly linear, primary - alkyl R and a monovalent cation M, preferably sodium.[2] The most frequently used example of this group of substances is sodium α-olefin sulfonate (INCI: Sodium C14-16 Olefin Sulfonate).[3]
R= Alkyl, M= Na+, n = 1 or 2
Production and composition
α-Olefin sulfonates are produced by sulfonation of alpha-olefins, typically using sulfur trioxide. This reaction produces two groups of products: (1) allylic and homoallylic sulfonic acids and (2) 5- and 6-membered cyclic sulfate esters. Base hydrolysis of the mixture gives alkene sulfonates (derived from simple deprotonation of allylic and homoallylic sulfonic acids) and 3- and 4-hydroxyalkanesulfonates (derived from the cyclic sulfate esters).[4] A typical mixture consists of 60-65% alkene sulfonates and 35-40% hydroxyalkane sulfonates. The commercially available olefin sulfonates are supplied as solutions containing about 40% active ingredient content.[5][6]
Description
In addition to a longer hydrocarbon chain in which there must be at least one double bond (hence the name "olefin"), it has an anionic sulfonate headgroup with a sodium ion as a counterion. The sulfonate group is negative in aqueous solution, which is why the α-olefin sulfonates are among the anionic surfactants. In contrast to most other surfactants in which the C12-alkyl chains have the highest surface activity, olefin sulfonates shows maximal activity when using C14and C16-olefins.[5]
Usage
α-Olefin sulfonates with linear alkenyl radicals from C12 to C18 are used as anionic surfactants in various areas of application due to their pronounced foam formation[clarification needed] and foam stability (even with high water hardness), excellent fat-dissolving power and oil dissolving power as well as a favorable ecological profile and low aquatic toxicity and human toxicity.[7][8] They are typically used in detergents and cleaning agents, for degreasing, in the emulsion polymerization, the conditioning of concrete and mortar as well as in the formulation of pesticides.[2][9]
Sodium C14-16 olefin sulfonate is being introduced in some shampoos as an alternative to sodium laureth sulfate. Some groups and sellers suggest that it is healthier, but this claim lacks evidence.[10]