Density functional theory study of the intramolecular [2 + 3] cycloaddition of azide to nitriles.

Density functional theory calculations using the hybrid functional B3LYP have been performed to study tetrazole formation by intramolecular [2 + 3] dipolar cycloaddition of organic azides and nitriles. Experimental reactivity trends are explained and rationalized in terms of a number of parameters, such as strain, tether length, and solvation and entropy effects. Interestingly, no correlation was found between the overall free energies and the free energies of activation of the reactions, due to the significant difference in strain and geometry between the transition states and products.