Exploring the potential energy surface of the catalyzed isomerization of nitrosomethane to formaldoxime

The mechanism of the isomerization of nitrosomethane to formaldoxime catalyzed by neutral molecule (H₂O and HCOOH) has been investigated at the level of B3LYP/6-311+G**. Calculated results indicate that the rearrangement from nitrosomethane to more stable irans-formaldoxime can proceed via two different reaction channels, but the favorable reaction pathway catalyzed by water and formic acid is different from the one in the catalyst-free reaction. It is more favorable that the tautomeric reaction involves the formation of cis-formaldoxime and a subsequent rotation about the N-O bond to form iroris-formaldoxime in the catalyzed reaction. The activation energy of rate-determining step was reduced from 197.9kJ/mol to 138.7kJ/mol in the water-catalyzed reaction and 79.6kJ/mol in the formic acid-catalyzed reaction, respectively, clue to the catalysis of hydroxylic groups, but the catalysis of more acidic hydroxyl group in the latter system has been shown to be more efficient. © World Scientific Publishing Company.