Kinetics of the reaction of benzoyl chloride andβ‐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 H 2 O/CH 2 C1 2 medium under inverse phase-transfer catalysis (IPTC) were investigated. Pyridine (Py), Pyridine 1-oxide (PNO) and 4-dimethylaminopyridine (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.