title: DFT Study and Monte Carlo Simulation on the Aminolysis of XC(O)OCH3 (X = NH2, H, and CF3) with Monomeric and Dimeric Ammonias.
abstract: The aminolysis of substituted methylformates (XC(O)OCH3, X = NH2, H, and CF3) in the gas phase and acetonitrile are investigated by the density functional theory B3LYP/6-311+G(d,p) method and Monte Carlo (MC) simulation with free energy perturbation (FEP) techniques. The direct and the ammonia-assisted aminolysis processes are considered, involving the monomeric and dimeric ammonia molecules, respectively. In each case, two different pathways, the concerted and stepwise, are explored. The calculated results show that, for the direct aminolysis, the activation barrier of the concerted path is lower than that of the rate-controlling step of the stepwise process for all three reaction systems. In contrast, for the ammonia-assisted mechanism, the stepwise process is more favorable than the concerted pathway. The substituent effects at the carboxyl C atom of methylformate are discussed. This aminolysis of substituted methylformates is more favored for X = CF3 than for X = H and NH2 in the gas phase for both the direct and the ammonia-assisted processes. Solvent effects of CH3CN on the reaction of HC(O)OCH3 + nNH3 (n = 1, 2) are determined by Monte Carlo simulation. The potential energy profiles along the minimum energy paths in the gas phase and in acetonitrile are obtained. It is shown that CH3CN lowers the energy barriers of all reactions.
authors.affiliation: College of Chemistry, Key Laboratory of Green Chemistry and Technology in Ministry of Education, Sichuan University, Chengdu 610064, P. R. China, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P. R. China, and Department of Chemistry, Inha University, Inchon 402-751, Korea.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Xia
authors.affiliation: College of Chemistry, Key Laboratory of Green Chemistry and Technology in Ministry of Education, Sichuan University, Chengdu 610064, P. R. China, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P. R. China, and Department of Chemistry, Inha University, Inchon 402-751, Korea.
authors.forename: Chenghua
authors.initials: C
authors.lastname: Zhang
authors.affiliation: College of Chemistry, Key Laboratory of Green Chemistry and Technology in Ministry of Education, Sichuan University, Chengdu 610064, P. R. China, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P. R. China, and Department of Chemistry, Inha University, Inchon 402-751, Korea.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xue
authors.affiliation: College of Chemistry, Key Laboratory of Green Chemistry and Technology in Ministry of Education, Sichuan University, Chengdu 610064, P. R. China, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P. R. China, and Department of Chemistry, Inha University, Inchon 402-751, Korea.
authors.forename: Chan Kyung
authors.initials: CK
authors.lastname: Kim
authors.affiliation: College of Chemistry, Key Laboratory of Green Chemistry and Technology in Ministry of Education, Sichuan University, Chengdu 610064, P. R. China, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P. R. China, and Department of Chemistry, Inha University, Inchon 402-751, Korea.
authors.forename: Guosen
authors.initials: G
authors.lastname: Yan