Intramolecular hydrogen transfer of N-substituted formamides has been examined by ab initio theoretical
calculation. The potential surfaces, the global isomeric structures, and the transition geometries of intramolecular
hydrogen transfer were determined at the MP2/6-31+G** level of calculation. The energy was further analyzed
by a single point calculation, MP2/6-311++G**//MP2/6-31+G**, and the use of G2 theory. There are E
and Z conformations in each substituted derivative. The calculated energy barrier for the intramolecular
hydrogen transfer (carbon−hydrogen to the carbonyl oxygen) of formamide is 76.14 kcal/mol. The Z form
of N-substituted formamides (regardless of the type of substituents, CH3, OH, and OCH3) all have lower
barriers; nevertheless, the E form counterparts show significant substitution effect. The methyl group decreases
the barrier by 1.35 kcal/mol, while the hydroxy and methoxy groups increase the barriers by 2.40 and 1.69
kcal/mol, respectively. The catalytic effect achieved by the added H2O or NH3 molecule to the formamides
is substantial. Energy barriers decrease around 26.5∼30.1 kcal/mol in most of the complexes and the transfer
mechanism of each complex is concerted.