A field ionization study of octan-2-one

H/D randomization is not observed within the octan-2-one-1,1,1,3,3-d₅ molecular ion at times less than 7 × 10^?10 sec following field ionization. Partial H/D randomization is observbed at 10^?6 to 10^?5 sec. It is deduced that the curves of microscopic rate constant k against internal excitation energy E for the reactions effecting randomization and for the McLafferty rearrangement intersect. The field ionization kinetics (FIK) for the McLafferty rearrangement in octan-2-one-1,1,1,3,3-d₅ are investigated over a time range extending from 10^?11 to 10^?6 sec. The maximum microscopic rate constant k for the reaction is estimated as 5 × 10¹⁰ sec^?1. It is suggested that FIK measurements with a double focusing mass spectrometer be made by sweeping the blade potential rather than by the alternative technique of sweeping the electric sector analyzer potential. The ‘normnal’ FI mass spectra of octan-2 one and octan-2-one and octan-2-one-1,1,1,3,3-d₅ are presented and discussed. It is proposed that the m/e 56 species in the ‘normal’ FI mass spectrum of octan-2-one represents a doubly charged ion formed by loss of oxygen in a surface process.