(adamantene), at least at the rate-determining transition state The ratio of CF3C!OOD/CF3COOH loss (m/z 134/m/z 135) is essentially constant at 0.8 over the time interval 140-1 320 ps. This value is reasonably taken as the kinetic isotope effect for a McLafferty rearrangement, since it is only marginally greater than the values 0.88 and 0.92 quoted for aliphatic esters6 On the other hand, the sig- nificant loss of deuterium from the position adjacent to the trifluoracetoxy ...