Kinetics of the reaction of some 3- and 5-substituted 2-furoyl and ortho- and para-substituted benzoyl chlorides with m-chloroaniline in benzene

Abstract

The rate of the reactions of some 3- and 5-substituted 2-furoyl chlorides and corresponding ortho- and para- substituted benzoyl chlorides with m-chloroaniline in benzene was measured. The log k values at 25° were correlated with Brown's σ⁺ constants and a slope greater than that for benzoylation was found. The results are in agreement with a two-step S_AN mechanism where the rate-determining step is the attack of the lone pair of the electrons of the amino-group on the carbonyl carbon atom. A variable σ⁺ value for the 2-furyl group was obtained. The substituent in the 3-position in the furan ring does not exert a steric effect on the rate.