61166-15-2Relevant articles and documents
EFFECT OF STRUCTURAL FACTORS ON THE KINETICS OF FORMATION AND REACTIVITY OF THE INTERMEDIATE PRODUCT IN ACYL TRANSFER REACTIONS CATALYZED BY IMIDAZOLES
Dadali, V. A.,Zubareva, T. M.,Litvinenko, L. M.,Simanenko, Yu. S.
, p. 1543 - 1551 (2007/10/02)
During the stage-by-stage investigation of the aminolysis of benzoyl halides catalyzed by N-substituted imidazoles in low-polarity media the effects of the structure of the reagents and of the intermediate product on the rate constants for the forward and reverse reactions and on the equilibrium constant of the first reversible stage were studied.The rate (k2) of the reaction of the intermediate product with the arylamines at the second rate-determining stage was also investigated.Compared with the noncatalytic reaction the first stage of the catalytic reaction is characterized by the formation of an earlier transition state, similar to a tetrahedral intermediate product.The equilibrium constants for the formation of the intermediate product do not depend on the effect of the substituent in the benzoyl fragment (which is due to the identical sensitivity of the forward and reverse reactions to this effect) but varies in relation to the basicity of the imidazole and the character of solvation of the anion in the intermediate product.The transition state of the k2 reaction is reagent-like with a small degree of formation and cleavage of bonds.A theory is formulated in with the reactivity of the acyl-ammonium halides in low-polarity media is determined by two factors: a) The "dipositive" character of the C-N bond, due to its "destabilization;" b) the additional stabilization of the transition state through general-base assistance from the anion.