Theoretical study on the mechanism of formation of cyanate resins

Ab initio Calculations of a formation reaction of a triazine ring were perf ormed. From the model substrate, methyl cyanate, a concerted association pa th with C-3h symmetry was first examined. In terms of energy changes, this path was found to be unlikely. Second, a stepwise path assisted by a water cluster was tested. But, this path was found to be of a relatively high amo unt of activation energy in the first additional step. Third, a zinc format e was used as a catalyst, and the reaction was computed to have a reasonabl e stepwise route for formation of the six-membered triazine ring. Fourth, t he reaction promoted by a hydronium ion was shown to generate a ring-closur e mechanism similar to that caused by the zinc catalyst. Thus, the crucial role of catalysts coordinated to the sigma lone-pair orbital of the cyanate nitrogen atom was verified.