title: Acid-catalyzed reactions of twisted amides in water solution: competition between hydration and hydrolysis.
abstract: The acid-catalyzed reactions of twisted amides in water solution were investigated by using cluster-continuum model calculations. In contrast to the previous widely suggested concerted hydration of the C=O group, our calculations show that the reaction proceeds in a practically stepwise manner, and that the hydration and hydrolysis channels of the C-N bond compete. The Eigen ion (H(3)O(+)) is the key species involved in the reaction, and it modulates the hydration and hydrolysis reaction pathways. The phenyl substitution in the twisted amide not only activates the N-CO bond, but also stabilizes the hydrolysis product through n(N)→π(phenyl) delocalization, leading exclusively to the hydrolysis product of the ring-opened carboxylic acid. Generally, the twisted amides are more active than the planar amides, and such a rate acceleration results mainly from the increase in exothermicity in the first N-protonation step; the second step of the nucleophilic attack is less affected by the twisting of the amide bond. The present results show good agreement with the available experimental observations.
authors: State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 360015, PR China.
authors: Binju
authors: B
authors: Wang
authors: Zexing
authors: Z
authors: Cao
mesh_terms: D000143:Acids / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry*; D002384:Catalysis; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D011789:Quantum Theory; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D000143:Acids; D000577:Amides; D012996:Solutions; D014867:Water; D002248:Carbon Monoxide