Kinetics of the reaction of benzoyl chloride and β‐methylalanine under inverse phase transfer catalysis

Abstract

The reactions of benzoyl chloride (PhCOCl) and sodium salts of five α‐amino acids ((R'NH)CHRCOOH) in a two‐phase H2O/CH2C12medium under inverse phase‐transfer catalysis (IPTC) were investigated. Pyridine (Py), Pyridine 1‐oxide (PNO) and 4‐dimethylamino‐pyridine (DMAP) were used as the inverse phase‐transfer catalysts. A high yield (85–100%) of the main product PhCO(NR')RCOOH was generally obtained. The order of reactivities of amino acids toward reaction with PhCOCl is (N‐methylglycine, L‐proline)≫glycine≫DL‐α‐alanine>β‐methylalanine≫acetic acid. The characteristics of the PNO‐catalyzed reaction of PhCOCl and sodium salts of β‐methylalanine are similar to those of the PNO‐catalyzed reaction of PhCOCl and sodium benzoate. The PNO‐catalyzed reaction of benzoyl chloride and sodium salts of β‐methylalanine follows a pseudo‐first order kinetics. The observed rate coefficient is a linear function of the concentration of pyridine 1‐oxide (PNO). The order of reactivities of catalysts in catalyzing the two‐phase reaction of PhCOCl and /3‐methylalanine is DMAP>PNO>Py. The experimental results are rationalized.