Etude par spectrométrie de masse de l'ionisation de benzonitriles, de phénylacétonitriles et de N,N‐diméthylanilines substitués

Molecular ionization potentials for series of compounds of the type XC 6 H 4 CN, XC 6 H 4 CH 2 CN and XC 6 H 4 N(CH 3 ) 2 have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σ p + constants than through Hammett's σ p values. No meta ‐ para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron‐releasing power of the original substituent. Ionization potentials calculated by using the semi‐empirical method of equivalent orbitals are in good agreement with the experimental values.