A PULSED ION SOURCE FOR THE STUDY OF UNIMOLECULAR AND BIMOLECULAR REACTIONS OF GAS-PHASE IONS

A pulsed ion source has been constructed for use with a magnetic-deflection mass spectrometer. With this source the time between ion formation and withdrawal for analysis can be controlled and varied in a known manner. The design and operating characteristics of the source are discussed and a technique is described for the measurement of ion withdrawal times using the pulsing technique. The rate constant for the ion molecule reaction[Formula: see text]has been determined for the reaction of thermal energy ions using reaction time as the experimental variable. The equivalent reactions in the deuteriomethanes have also been studied. Preliminary results obtained in the study of the unimolecular fragmentation of the cyclohexadiene, toluene, and spiroheptadiene parent ions are presented.

AN ELECTRON IMPACT STUDY OF SOME C8HI0 ISOMERS

The mass spectra of 1-, 2-, and 6-methylspiro[2.4]hepta-1,3-diene have been measured and found to be very similar to the spectra of 7-methylcycloheptatriene and the isomeric alkyl benzenes. It is concluded that in all cases the major part of the fragmentation occurs by identical paths involving identical intermediates. This conclusion is supported by deuterium labelling and appearance potential data. On the other hand the mass spectrum of 2,5-dimethyl-1,5-hexadien-3-yne, an acyclic C8H10 isomer, shows a number of significant differences in its fragmentation pattern. These differences are reflected in the energetics of ion formation and it is concluded that in this case the fragmentation proceeds through different intermediates.

IONIZATION POTENTIALS OF METHYL-SUBSTITUTED BENZENES AND CYCLOPENTADIENES

The ionization potentials of a number of methyl-substituted benzenes and cyclopentadienes have been measured by electron impact. The experimental results are compared to calculations based on a group orbital method.

AN ELECTRON IMPACT STUDY OF METHYL PHENYL ETHERS

The mass spectra of anisole, anisole-methoxy-d3, meta and para methylanisole, meta and para methyl-d3-anisole, and meta and para niethylanisole-methoxy-d3 have been recorded. From the deuterium labelling and appearance potential studies, the main fragmentation paths on electron impact have been elucidated. The energetics of formation of the CH3OC7H6+ ion from the methylanisoles, benzyl methyl ether, 7-methoxycycloheptatriene, and the ethylanisoles have been studied.

AN ELECTRON IMPACT STUDY OF METHYLMERCAPTOBENZYL CHLORIDES

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