Theoretical Study on the Pyrolysis of Sulphonyl Oximes in the Gas Phase

초록

The reaction mechanism of the pyrolysis of sulphonyl oximes (XC6H4-S(O)2O-N=C(H)-C6H4Y in the gas phase has been studied theoretically at HF/3-21G, ONIOM (B3LYP/6-31G** : HF/3-21G) and ONIOM (MP2/6-31G** : HF/3-21G) levels. All the calculations show that the thermal decomposition of sulphonyl oximes is a concerted asynchronous process via a six-membered cyclic transition state. The activation energies (Ea) predicted by ONIOM (B3LYP/6-31G** : HF/3-21G) method are in good agreement with those experimental results for a series of tosyl arencarboxaldoximes. Four substituents, X, Y=p-CH3, p-Cl, m-Cl and p-NO2, were used to investigate the substituent effect on the elimination. The interaction between two substituents, X and Y, was discussed.