THE STRUCTURE AND MOBILITY IN AIR OF PROTONATED KETONES

The mobility in air, at 200-degrees-C, of protonated ketones was studied by ion mobility spectrometry. A linear correlation was found between the inverse reduced mobilities of these ions and their masses. However, more subtle effects from which structural information could be derived were also observed. With regard to alkyl ketones the protonated 2-ketones, had lower mobilities than their isomers, and branched alkyls were more mobile than their normal isomers. Alkyl-aryl ketones, cyclic ketones and alkoxy ketones had higher mobilities than isobaric alkyl ketones. These results resemble those observed for protonated aliphatic and aromatic amines, and indicate that the more compact the structure of the ion the higher its relative mobility.