A Theoretical Study On The 1,3-Dipolar Cycloaddition Of C, N-Dimethyl Nitron And Acrylonitrile

The 1,3-dipolar cycloaddition reaction is very important in the synthese of the organic and functional molecule, and it is significant to ravel its reaction mechanism. It can foreshow the constitute of products and redound to the design of compose routes. The 1,3-dipolar cycloaddition reaction of C,N-dimethyl nitron and acrylonitrile has been caculated at MP2/6-31G levels by using ab initio molecular orbital theory. The structures of the reactants , transition states and products are are completely optimized by the Berny energy gradient technique and the transition states are characterized by vibration frequency analysis. The two reactions are found to proceed via a concerted mechanism and are nitron(HOMO) and acrylonitrile (LUMO) controlled. This reaction can lead to four products of endo-4, exo-4, endo-5 and exo-5 and the energy barriers of four reactions are 23.78,33.06,6.31and7.82kJ mol-1 respectively .Two H-bond complexes were produced first when C,N-dimethyl nitron approaching to acrylonitrile, and their relative energies are -52.67 and -52.50 kJ mol-1.The theoretical study results show that the substituent at 4- position can proceed more easily than that at 5-position having a good regio-selectivity. The energy barrier of the reaction forming endo product is not much more than that of exo one, so the reaction should be a competitive mechanism. This paper consists of four parts: The first part of the paper is preface ,it describes the significance of quantumn chemistry and it introduces briefly the content that will be discussed. The second part of the paper makes a introduction of the backround and the content of the theoty that will be used in the paper. The third part of the paper expounds the theory and application of transition states. The fourth part of the paper makes the Theoretical Study on the 1,3-Dipolar Cycloaddition of C,N-Dimethyl Nitron and Acrylonitrile.