ortho-Effects on ordering factors in mass spectral rearrangements. Loss of keten from halogenated phenyl acetates and acetanilides

Abstract

Williams's adaptation of the early form of the dependence of rate constant on energy used in quasi-equilibrium theory is employed to evaluate trends in factors influencing rates when substituents are introduced ortho to the functional group of phenyl acetate or acetanilide. In the phenyl acetates, the greatest tightening of the activated complex for loss of keten is found when the ortho-substituent is fluorine. The loss of keten from acetanilides is affected by two opposing trends due to ortho-substitution; the greatest retardation by an ortho-substituent occurs when the halogen is chlorine. An assignment of effects is attempted. It seems possible to document steric effects in molecules of moderate complexity in this way in the same fashion as differences between appearance potential and ionisation potential are now used to document electronic effects of substituents on mass spectral reactions.