Density functional theory (DFT) and ab initio methods were used to study gas phase pyrolytic reaction mechanisms of N ethyl, N isopropyl and N t butyl substituted 2 aminopyrazine at B3LYP/6 31G * and MP2/6 31G *, respectively. Single point energies of all optimized molecular geometries were calculated at B3LYP/6 311+G(2d,p) level. Results show that the pyrolytic reactions were carried out through a unimolecular first order mechanism which were caused by the migration of atom H(17) via a six member ring transition state. The activation energies which were verified by vibrational analysis and correlated with zero point energies along the reaction channel at B3LYP/6 311+G(2d,p) level were 252.02 kJ·mol -1 ( N ethyl substituted), 235.92 kJ·mol -1 ( N isopropyl substituted) and 234.27 kJ·mol -1 ( N t butyl substituted), respectively. The results were in good agreement with available experimental data. Density functional theory (DFT) and ab initio methods were used to study gas phase pyrolytic reaction mechanisms of N ethyl, N isopropyl and Nt butyl substituted 2 aminopyrazine at B3LYP / 6 31G * and MP2 / 6 31G *, respectively. Single point energies of all optimized molecular geometries were calculated at B3LYP / 6 311 + G (2d, p) level. Results show that the pyrolytic reactions were carried out through a unimolecular first order mechanism which were caused by the migration of atom H (17) via a The activation energies which were verified by vibrational analysis and correlated with zero point energies along the reaction channel at B3LYP / 6 311 + G (2d, p) level were 252.02 kJ · mol -1 (N ethyl substituted) , 235.92 kJ · mol -1 (N isopropyl substituted) and 234.27 kJ · mol -1 (N t butyl substituted), respectively. The results were in good agreement with available experimental data.