The effect of substituents on the Lewis acidity of α-cyanostilbenes

Abstract

The effect of substituents in the two aromatic rings of α-cyanostilbene on the Lewis acidities of these compounds towards alkoxide ions has been examined. Substituents in the β ring produce effects on the acidity which correlate with the σ values of the substituents and yield an average ρ value of + 2.22. Substituents in the α ring, however, are correlated by the σ− values and yield an average ρ value of + 4.62. A p-nitro group in the α ring exhibits a greatly enhanced σ− value (+ 1.73).