مشخصات پژوهش

The Diels–Alder (DA) reaction is one of the most valuable reactions in preparative organic synthesis between a conjugated diene and a dienophile.1-3In this work the DA reactions of X2C=NNH2 (X= H, F, Cl, Br) with 1,3-butadiene was theoretically studied. At first, the influence of various substituents on the activation barriers these reactions were studied. Then the relationship between activation energies these reactions and distortion energies of fragments in cycloaddition was investigated. The distortion energy is defined as the energy required to distort the fragments into the geometry they possess in the transition state, without allowing interaction between the fragments.4-6 Thus, the activation energy of a reaction can be expressed as the sum of the distortion energy and the interaction energy between addends involved in the transition state. The results show that the fluorine more than other substituents, decreases the activation barrier of formation of DA reaction X2C=NNH2 (X= H, F, Cl, Br) with 1,3-butadiene. The results also show that there is a good correlation between activation energies and distortion energies for all the DA reactions studied here (Scheme 1).