The ‘preference factor’ and isotope effect in the loss of hydrogen or deuterium from labeled toluenes

Metastable ion decompositions involving the loss of hydrogen and deuterium from partially deuterated toluene ions were studied using a double focusing mass spectrometer. The electric sector voltage was adjusted so that the only ions transmitted were those which lost a particular fraction of their kinetic energy in decompositions taking place in front of the electric sector. Transitions involving loss of mass 1 or mass 2 from the molecular ions of toluene‐α‐ d 3 and toluene‐2,3,4,5,6‐ d 5 were studied. The results showed that in these slow reactions, the ‘preference factor’ defined as the ratio of the probability of loss of a hydrogen atom from a side‐chain position to loss of a hydrogen atom from a ring position was 1.00. The ‘isotope factor,’ defined as the ratio of the probability of loss of a hydrogen atom from any position to that for the loss of a deuterium atom from the same position was found to be 3·50.