Alkyl benzyl sulphonates/ Alkyl benzene sulphonates (ABS)
Main components of anionic detergents-surface active with polar (water soluble) sulphate and nonpolar alkyl end
Aid in emulsification of fatty substances and cleaning occurs while these molecules make a monolayer around lipophilic droplets or particles.
Their molecules orient with their nonpolar end towards the lipophilic substance and the sulphonate end towards water.
Nonlinear alkylbenzene sulphonates or Branched alkylbenzene sulfonates (BAS) are recalcitrants and resistant to biodegradation and cause foaming problems in sewage treatment and in the rivers.
ABS are easier to manufacture and bear superior detergent properties but the methyl branching of alkyl chain in them interferes with biodegradation of ABS, because tertiary carbon atom blocks the normal β-oxidation.
Nonlinear alkylbenzyl sulphonates or Branched alkylbenzene sulfonates (BAS) were replaced with linear alkylbenzene sulfonates (LAS) during the 1960s due to environmental concerns
LAS (linear alkylbenzyl sulphonates) are biodegradable
It is biodegraded rapidly under aerobic conditions within weeks- oxidative degradation initiates at the alkyl chain.
Under anaerobic conditions it degrades very slowly or not at all, accumulates in sewage sludge, but once oxygenated, it will rapidly degrade
Thus, BAS to LAS conversion is a story where a synthetic molecule was redesigned to remove obstacles to biodegradation, while preserving the other useful characteristics of the compound.
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