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Category name:
Alkylbenzene derivatives

Justifications and discussions

Category definition:
The two major types of substances included in this category are linear alkylbene (LAB) and linear alkyl benzene sulfonic acids, branched alkylbenzene sulfonic acids and their salts (LABS, LABS Na, HiMo LAB, HiMo LABS and TSA C20-24).
LAB is a mixture of phenylalkanes with the attachent of the alkyl chain occurring on any of the internal carbons. LAB derivatives are precursors to produce the surfactant LABS after addition of a sulfonyl group. LABS are based on the reaction of an alpha olefin with benzene, in the presence of sulphuric acis, with or without a catalyst. Sodium hydroxide or some other salt is used to neutralize. They consist of a sulfonated aromatic ring and a linear alkyl chain at the para position. They are anionic surfactants and are characterized by the presence of both a hydrophilic group and a hydrophobic group (alkyl chain) leading to amphophilic properties. Chain lengths can vary but are predominantly in the range of C10 to C14. Most commercial LABS products are mixtures. They are the major cleaning agent or surfactant used in various household detergents. HiMo LAB is produced from alkylation reaction of alpha olefins with excessive benzene at high temperature. High molecular weight LABS or HiMo LABS is a co-production stream for use in lubricant detergents such as oils and industrial applications. One type of branched alkyl benzene sulfonic acid derivative is TSA C20-24. This is similar to hiMoLABS, but has a branched alkyl chain and an additional merhylgroup attached to the benzene group.
Category rationale:
The chemicals in this category are salts or acids of structurally related linear alkylbenzene (LAB) and sulfonates (LABS). These molecules are characterized that are molecules characterised by a hydrophobic tail and a hydrophilic head. All the chemicals in this group consist of a benzene ring with or without a sulfonic acid substituent group and an alkyl chain that can vary in length and extent of branching. LABS are manufactured by reacting the alkylbenzenes with sulfuric acid or sulfur trioxide to give the corresponding sulfonic acid, which is neutralized to form the desired salt (IPCS, 1996).
All substances within the category are considered to have similar physicochemical properties, such as low water solubility; low vapour pressure; high viscosity, density and melting points; and relatively high molecular weights. The solubility could potentially differ based on the alkyl chain length, usually decreasing with increasing chain length. Although the carbon chain length in this group of chemicals varies, they all are expected to have essentially similar physicochemical properties.
Most of the chemicals in this group have similar end uses, typically in lubricating oils and cleaning products. The salts are expected to dissociate almost completely below the critical micelle concentration. The chemicals in this group are expected to have similar toxicity, which is primarily due to the alkylbenzene sulfonate anion.

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