Pathways of the reaction of nucleophilic addition of ammonia to formaldehyde in the gas phase and in the complex with formic acid: ab initio calculations

The gradient pathways of the reaction of nucleophilic addition of ammonia to formaldehyde were calculated for free molecules and in the NH3-H2CO-HC(O)OH complex by the ab initio RHF/6-31G**, MP2(fc)/6-31G**, and MP2(full)/6-311++G** methods. Both reactions proceed concertedly. In the first case, the reaction successively passes through two transitional states with an energy barrier exceeding 35 kcal mol(-1). In the case of the complex with formic acid, the reaction follows a conventional pathway, although its activation barrier calculated by the RHF/6-31G** and MP2(fc)/6-31G** methods decreases to 12.6 and 3.8 kcal mol(-1), respectively.