Spiro Compound Ring Stress, Heat Of Formation And Theoretical Study On The Rearrangement

The ring strain energies, heats of formation and rearrangement mechanism of the selected spiro-compounds were investigated by using DFT methods. In this thesis, we systematically studied the 1-Methylene-2-vinylcyclopropane,3-methylenecyclopentene, 1-cyclopropylidene-2-vinylcyclopropane and 4-methylenespiro[2,4]hept-5-ene systems. The reaction models were employed to calculate the ring strain energies of the selected systems. The computational results indicated that the ring strain energies of the systems which were computed at the B3LYP/6-311G(d,p) level by using the Hyperhomodesmotic model have good agreements with the experimental values. We have a prediction that if the structure of the spiro-compounds contains the cycloalkene, the ring strain energy declines with increasing ring number, and while the stability of the system also increases. Twelve methods were used to compute the formation heat of the system. By comparison with the experimental values, among the 12 methods, the computational results indicated that the formation heat of the system calculated by the B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and B3LYP/6-311++G(2df,2p) methods are more close to the experimental values, and the computational results coming from the B3LYP/6-311++G(2df,2p) method has the best agreement with the experimental values among the three methods. According to the results, we can also know that the rearrangements of 1-Methylene-2-vinylcyclopropane to 3-methylenecyclopentene, 1-cyclopropylidene-2-vinylcyclopropane to 4-methylenespiro[2,4]hept-5-ene are single-step channels.