Abstract: The isomerization reaction of hydroxylamine H_2NOH rearrangement to ammonia oxide H_3NO was investigated by ab initio MO calculations using RHF/4-31G basis set. The energy gradient method was used to optimize the equilibrium geometries of H_2NOH, H_3NO and the transition state. The activation enthalpy, activation energy, frequency factor, free energy of activation , reaction rate constant and equilibrium constant were calculated. The reaction ergodography was analyzed by means of intrinsic reaction coordinate (IRC) method. The vibrational analyses of H_2NOH, H_3NO, and the reaction coordinate have been made by the numerical differentiation method. The vibrational frequency correlation diagram along the IRC has been plotted and a vibrational excited state of OH bond is anticipated before the transition state.

Key words: Hydroxylamine, Rearrangement reaction, Ab initio