Study on D-A Reaction Mechanisms of 1,3 Cyclohexa-diene with Propionitrile

Six possible Diels-Alder reaction channels of 1,3 cyclohexa-diene with propionitrile leading to two types of exo and endo products have been studied by using ab initio method at 3-21G level.The calculated results show that the favorite path for both exo and enso products is a stepwise process,in which the terminal carbon of propionitrile attacks the carbon in ring at the first step.The actibation barrers for the rate-detdrmining steps to form exo and endo products are 50 17 and 50 67kJ/mol,respectively and the exo one is slightly lower than endo one.