Hydrogen migrations in mass spectrometry. IV—formation of [C6H7]+ in the chemical ionization mass spectra of alkylbenzenes

✍ Scribed by Hei-Wun Leung; Alex. G. Harrison

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 450 KB
• Volume: 12
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210120912

✦ Synopsis

Using specific deuterium labelling the mechanisms of the olefin elimination reactions leading to formation of [C,H,]+ in the H, and CH, chemical ionization mass spectra of ethylbenzene and n-propylhenzene (and to [C,H,C,HJ+ in the CH, chemical ionization mass spectra) have been investigated. The results show that the reaction does not occur by specific migration of H from the f3 position of the alkyl group to the benzene ring. For ethylbenzene 23-29% of the migrating H originates from the a-position, while for n-propylbenzene H migration from all propyl positions is observed in the approximate ratio, position 1:position 2:position 3=0.30:0.22:0.48. It is proposed that the results can be explained on the basis of competing H migration from each alkyl position involving cyclic transition states of different ring sizes, rather than by H randomization within the alkyl chain.