Mechanism on the Hydrolysis of Cinnamonitrile in Strong Acid

Rate constants for the hydrolysis of cinnamonitrile in the concentration range of 1 ∼ 5M of perchloric acid at 25C have been determined by UV spectrophotometry and from the Bunnett equations, hydration parameters ( = 9.8, = 0.42 & =1.6) were obtained. CNDO/2 MO calculations were performed to determine relative stability, net charges, and overlap population of various conformational isomers. The results show that the (E)-planar is more stable than the (Z)-planar and protonation is favored on the nitrogen atom. On the basis of above findings, the acid hydrolysis is initiated by the protonation of the nitrogen atom of cinnamonitrile and then water molecule acting as nucleophile and as a proton transfer agent in the rate determining step. In the transition state of the acid hydrolysis, nucleophilic addition of water molecule occurs by sigma approach to the positively charged ) atom of the conjugate acid. As the results, we may conclude that the hydrolysis of cinnamonitrile in the strong acidic media proceeds through the A-2 type mechanism