Five mono cycle β Lactams’ structures were optimized by semi empirical AM1 method of quantum chemistry.The ring opening reaction mechanism of mono cycle β Lactams in the presence of base were studied.The geometric configurations of reaction transition states and reaction products were calculated.At the same time,the law of electronic transference in reaction was found.
The reaction of the CH3 radical with molecular HNCO was examined using MP2 method at the 6311++g**basis set level.The geometry configures of reactants,intermediates,transition states and products were optimized.The result shows that the reaction CH3+HNCO→CH4+NCO is an absorbing hydrogen atomprocess,and there is a hydrogenbond complex(M) produced by the interaction of reactants,the energy of which is 813kJ/mol,less than that of the reactants.
UMP2 method was performed to study the reaction mechanism of CH2 with HNCO.The geometrical configurations of reactants,intermediates,transition states and products were optimized by UMP2 method at the 6-311++G（d,p）level.The energies of stationary points along the pathways were calculated at QCISD（T）/6-311++G（d,p）.Intermediates and transition states were confirmed by the results of vibration analysis and IRC calculation.From the results of the reaction mechanism of CH2 with HNCO,it is shown that in this reaction there exist three pathways,which are CH2（S）+HNCO→IM1→TS1→CH3+NCO;CH2（S）+HNCO→IM2→TS2→CH2CONH,CH2（T）+HNCO→IM3→TS3→CH2NH+CO,and CH2（T）+HNCO→IM3→TS3→CH2NH+CO.
