Stability of hydroxylamine isomers in aqueous solution: Ab initio study using continuum, cluster-continuum and Shells Theory of Solvation

The relative stability of the NH2OH and NH3O isomers of hydroxylamine in aqueous solution was investigated at ab initio CCSD(T)/TZVPP+diff level for gas phase energy and Shells Theory of Solvation (STS) method for solvation contribution. Our calculations point out that the zwitterionic form (NH3O) is only 3.5 kcal mol−1 less stable than the normal isomer (NH2OH). The solvation contribution obtained by the SM8 and SM8AD models are in close agreement with the STS calculations, whereas the PCM (or CPCM) and cluster-continuum methods need small cavities for predicting the correct stability value.