MCPA-butyl is produced by first generating and purifying technical-grade MCPA acid through the standard industrial sequence of para-cresol chlorination followed by carboxylation to form the phenoxyacetic acid. The purified acid is then esterified with n-butanol in the presence of an acid catalyst, with the reaction typically run under conditions that continuously remove water so the equilibrium favours formation of the butyl ester. Once the desired conversion is reached, the mixture is neutralised and washed to remove residual catalyst and unreacted alcohol, and the crude ester is refined, often by vacuum distillation, to meet technical specifications.
