Electron‐impact studies. LXXXIV—Substituent effects in the negative ion mass spectra of aryl esters

Linear plots may be obtained for the fragmentations of aryl p ‐cyanobenzoates using the McLafferty approach, but the correlations are not as satisfactory as those observed 1 for aryl nitrobenzoates. Some satisfactory correlations of substituent effects are noted in the negative ion spectra of substituted benzyl‐ p ‐nitrobenzoates and substituted phenyl‐( p ‐nitrophenyl)acetates. Pronounced rearrangement peaks are observed in the spectra of substituted phenyl‐( p ‐nitrophenyl)acetates. Appearance potential studies suggest that the similarities in ρ values obtained 1 for the fragmentations of aryl m‐ and p ‐nitrobenzoate molecular anions are probably due to the correspondence between Hammett σ values and appearance potentials in the two series.