Kinetic shift in some para-substituted acetophenones

An Atlas CH4 mass spectrometer has been used in conjunction with the electron ‘Energy Distribution Difference’ technique to investigate the kinetic shift associated with the process of elimination of CH₃ from acetophenone, p-methylacetophenone, p-chloroacetophenone, p-fluoroacetophenone and p-methoxy-acetophenone. The heats of formation of the ions investigated have been calculated.