Ab initio study of tautomerism and hydrogen bonding of beta-carbonylamine in the gas phase and in water solution

All the possible conformations of the three tautomeric isomers of simple be ta-carbonylamine were Fully optimized at ab initio MP2/6-31G** and B3LYP/63 1G** levels in order to determine the conformational equilibrium and the en ergies of the O-H ... N and O ... H-N hydrogen bridges. For the most intere sting conformations, further calculations in water solution were also carri ed out. It was found that carbonylamine is the most stable tautomer, follow ed by enolimine and carbonylimine. This order of stability does not change in solution. O-H ... N is the strongest hydrogen bridge, but in solution it s energy as well as that of the O ... H-N one are dramatically lowered. The deprotonation energy was also calculated and discussed.