Substituent Effects in Nonaromatic Unsaturated Systems

Sigma- and Pi-Electron Delocalization: Focus on Substituent Effects

“…However the most common problems involving the substituent effects are those in which the substituent affects the chemical or physicochemical properties associated with some functional group (often named a reaction site) attached to the same molecular moiety, most frequently a cyclic π-electron system. For the noncyclic π-systems, see ref . Sometimes a different treatment is in use, where a functional group being attached to various positions of the benzenoid hydrocarbons exhibits changes in its physicochemical characteristic.…”

On differences in substituent effects in substituted ethene and acetylene derivatives and their boranyl analogs

“…where ρ is the so-called reaction constant that describes the sensitivity of the reaction under study (physicochemical process) to the effect of X. Hammett substituent constants represent the numerical characteristics of electron accepting/donating properties of substituents and have become a very convenient way for describing most of substituent effects encountered in physical organic chemistry. Then, an avalanche of papers has appeared that have undertaken these problems presented and summarized in a numerous reviews and monographs [3][4][5][6][7][8][9][10][11].…”

“…In the studies presented here, 27 X substituents with the full spectrum of electronic properties are used, from strongly electron-withdrawing to strongly electron donating, as described by the Hammett σ p constant. As for historical reasons [1,2], the substituent constants are commonly used only to describe substituent effects on various benzene derivatives [3][4][5][6][7][8][9][10][11][12], one of the main and most interesting aims of this research is to investigate the applicability of the substituent constant σ p in describing substituent effects in X-substituted ethene and acetylene derivatives. This is the first study of this issue.…”