ON THE VALIDITY OF THE CONSTANTS OF IONIC SUBSTITUENTS - SUBSTITUENT EFFECTS ON THE CYANO STRETCHING FREQUENCIES AND INTENSITIES TRANS-ALPHA-PHENYL-BETA-ARYLACRYLONITRILES

Fourier-transform IR frequencies v(C drop N) and integrated intensitie s A(C drop N) of the cyano groups of a series of trans-alpha-phenyl-be ta-arylacrylonitriles (51 compounds) have been measured. Both v(C drop N) and the square roots of A(C drop N) of the neutral m- and p-substi tuted compounds (34 examples) have been found to correlate satisfactor ily with sigma(+) substituent constants, as well as according to the e quation of Yukawa-Tsuno. Diortho-substituted compounds deviate strongl y from the correlation lines because of the steric ortho-effects mainl y. sigma(+) (and other) constants of ionic substituents (seven example s) have proved satisfactorily valid in the series studied. The transmi ssion coefficient of the C=C double bond in the series has been estima ted to be 0.7.