At the B3LYP/6-311＋＋G(d,p) level, the first time computational study was performed on the interconversion mechanism between a series of double-substituted ammonium oxide (R2HNO) and double-substituted hydroxylamine (R2NOH) isomers with R＝CH3, NH2, OH, F, CH2CH3, CH(CH3)2 and C(CH3)3. Comparisons were made with the mechanism of H3NO and H2NOH. It was shown that relative to the double-substitued hydroxylamine (R2NOH), the increase of the electronegativity of R in the order of H＜CH3＜NH2＜OH＜F could raise both the thermodynamic and kinetic stability of the double-substituted ammonium oxide (R2HNO). In addition, for the alkyl substituents R [R＝CH3, CH2CH3, CH(CH3)2 and C(CH3)3], the greater steric effect would result in the higher thermodynamic stability, and also certainly increased kinetic stability, though not so noticeable. For the newly considered seven substituents [R＝CH3, NH2, OH, F, CH2CH3, CH(CH3)2 and C(CH3)3], the conversion barrier from R2HNO to R2NOH is as large as 27.0～56.3 kcal/mol. This indicates that all of them might be probably characterized in gas-phase.

Key words: R2HNO, R2NOH, isomer, thermodynamic stability, dynamic stability