MCPA-butotyl is produced by first manufacturing 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 the branched C4 alcohol sec-butanol (the “butotyl” alcohol) in the presence of an acid catalyst, with the reaction run under conditions that continuously remove water so the equilibrium favours ester formation. After the desired conversion is reached, the reaction mixture is neutralised and washed to remove residual catalyst and unreacted alcohol, and the crude ester is refined, often by vacuum distillation, before being formulated.
