Spontaneous and catalyzed isomerizations of the acetamide radical cation

✍ Scribed by Philippe Mourgues; Julia Chamot-Rooke; Hristo Nedev; Henri-Edouard Audier

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 136 KB
• Volume: 36
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.106

✦ Synopsis

Spontaneous and catalyzed isomerizations of the acetamide radical cation

The use of mass spectrometry for the study of peptides (sequencing, cationization, H-D exchanges, etc.) is a rapidly growing field. 1 Therefore, the chemistry of ionized amides, studied by mass spectrometry, is of considerable interest. This letter reports some new findings concerning the unimolecular and bimolecular chemistry of ionized acetamide, mainly focused on spontaneous and catalyzed 1,3-H migrations, resulting in tautomerization of the acetamide radical cation.

Among the four possible tautomers 1-4 of ionized acetamide (Scheme 1), only 1 and 2 have been experimentally described, 2 although no definitive proof was given of their structures. Structure 1 was assigned on the basis of direct electron ionization of acetamide, and structure 2 was logically given to the m/z 59 ion from ionized hexanamide, as the most stable fragment resulting from the McLafferty rearrangement.