Electron Ionization Mass Spectra of 1-(1-Naphthyl)ethyl Phenylacetates: a Study of Radical Cation Rearrangements

✍ Scribed by Stuart Grossert, J.; Bradley Yhard, G.; Pincock, James A.; Curtis, Jonathan M.

• Book ID: 102646246
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 530 KB
• Volume: 31
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199607)31:7<761::aid-jms351>3.0.co;2-i

✦ Synopsis

A series of esters, including three specifically deuterated esters, was prepared from 1-(1-naphthy1)ethanol and phenylacetic acids having different phenyl substituents. The electron ionization (EL) mass spectra revealed the formation of the expected cleavage ions, plus two types of rearrangement ions. The formation of one type of rearrangement ion from M+' is shown to involve a process in which a benzylic hydrogen atom migrates to the naphthyl side of the ester. Subsequent cleavage results in a radical cation, a, whose structure was investigated by tandem mass spectrometric (MS/MS) experiments. The other type of rearrangement ion, b, is apparently formed by a regular McLafferty-type process with hydrogen transfer from the ethyl chain to the acid side of the ester. An MS/MS experiment on molecular ions from 1-(1-naphthyl)ethanol, which are isobaric with a, showed the presence of two fragmentation pathways, one pathway being similar to that seen for the esterderived ion u and the other a simple a-cleavage process. The mechanistic study was supported by accurate mass measurements on all relevant ions.