A Theoretical Study of the Relationship between the Electrophilicity ω Index and Hammett Constant σ in [3+2] Cycloaddition Reactions of Aryl Azide/Alkyne Derivatives.

The relationship between the electrophilicity ω index and the Hammett constant σ has been studied for the [2+3] cycloaddition reactions of a series of -substituted phenyl azides towards -substituted phenyl alkynes. The electrophilicity ω index-a reactivity density functional theory (DFT) descriptor evaluated at the ground state of the molecules-shows a good linear relationship with the Hammett substituent constants σ. The theoretical scale of reactivity correctly explains the electrophilic activation/deactivation effects promoted by electron-withdrawing and electron-releasing substituents in both azide and alkyne components.