Synthesis and chemical hydrolysis of surface‐active esters

Abstract

AbstractA series of four homologous pure nonionic surfactants, all monoesters of tetra(ethylene glycol), were synthesized. The ester surfactants varied in the degree of substitution on the α‐carbon of the acyl chain, from no substitution to 2‐methyl, to 2‐ethyl, and on to 2,2‐dimethyl. All surfactants were based on C8‐acids except the 2‐methyl‐substituted, which was based on a C7‐acid. The ester surfactants were characterized by critical micelle concentration (CMC) and cloud point. Base‐catalyzed hydrolysis was investigated by using 1H NMR and tensiometry. The surfactants showed a pronounced difference in hydrolytic reactivity; the nonsubstituted surfactant was 90 times more reactive than the disubstituted, and the reactivity of the methyl‐substituted surfactant was 14 times more reactive than the ethyl‐substituted. Hydrolysis studies above the CMC revealed that the ester bond of the aggregated surfactant is protected from attack by hydroxide ions; thus, only surfactants in monomeric form are being cleaved.