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Theoretical study on the reaction mechanism of the alcoholysis of isocyanates
Author(s) -
Tang MingSheng,
Fu XiaoYuan
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560420303
Subject(s) - chemistry , isocyanate , methanol , computational chemistry , reaction mechanism , ab initio , isocyanic acid , nucleophile , reaction rate constant , acceptor , photochemistry , organic chemistry , kinetics , catalysis , polyurethane , physics , quantum mechanics , condensed matter physics
In this paper, the reactions of HNCO or CH 3 NCO with methanol have been studied using the ab initio MO method. The geometries of the reactants and products have been optimized by the energy gradient method. The calculated results are in accordance with experiment. Using Powell's method, by the minimization of the Euclidean norm σ of the gradient, the structures of the transition state ( TS ) for the two reactions were obtained. The structures have been further confirmed as TS by finding that there is one and only one negative eigenvalue for their force constant matrix. The imaginary vibration mode corresponding to the TS was also discussed. The calculated activation barriers of these two reactions are 96.02 and 95.13 kJ/mol, respectively. It can be concluded that the alcoholysis reaction of isocyanate is a nucleophilic addition reaction with methanol as an electronic donor and isocyanate as an acceptor and that the hydroxyl hydrogen of CH 3 OH plays an important role in the reaction.