An Ab initio study of tautomerism between formhydroxamic acid and formhydroximic acid

AbstractAb initio MO calculations including electron correlation with the 4‐31G and 4‐31G** basis sets were performed in order to study the formhydroxamic acid‐formhydroximic acid tautomerism. The geometries, relative energies, and activation energy of the tautomer and transition state were determined. Based on total‐energy calculations at the MP4/4‐31G**//RHF/4‐31G** plus the scaled zero‐point vibration energy level, the energy of formhydroxamic acid is determined to be lower than that of formhydroximic acid by 40.7 kJ/mol. The activation energy of the formhydroxamic acid‐formhydroximic acid tautomerism via a 1,3‐intramolecular hydrogen shift is 151.4 kJ/mol. © 1992 John Wiley & Sons, Inc.