Nucleophilic substitution reactions of cinnamoyl chlorides with anilines in acetonitrile and acetonitrile–methanol mixtures

Abstract

Kinetic studies on the solvolysis (in McOH–MeCN mixtures) and aminolysis (with anilines in McCN) of cinnamoyl chlorides have been carried out at 25.0 °C. The relatively large negative values of ρ_Y⁺=–0.9 ∼–1.5 for the methanolysis are consistent with a dissociative S_N2-like mechanism. For the aminolysis, the ρ_Y values are positive (ρ_Y= 0.52 ∼ 1.64) and ρ_X values range from –1.68 to –2.51 in acetonitrile. The positive values of β_X= 0.6–0.9 and ρ_XY= 0.88 in acetonitrile, and isotope effect data suggest that the aminolysis proceeds by a stepwise mechanism with rate-limiting breakdown of the tetrahedral intermediate, T^±. It is noted that in the acyl-transfer reactions proceeding by rate-limiting departure of the leaving group from the tetrahedral intermediate the signs of both ρ_Y and ρ_XY are positive and the reactivity–selectivity principle (RSP) is valid in general.