Stereospecific Fragmentation of 3-Dimethylaminocyclohexanols upon Electron Impact Ionization

✍ Scribed by Vais, V.; Mandelbaum, A.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 339 KB
• Volume: 32
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199707)32:7<750::aid-jms527>3.0.co;2-y

✦ Synopsis

Stereoisomeric cisand trans-1-butyl-3-dimethylaminocyclohexanols have been previously reported to exhibit different electron impact (EI) mass spectra. The m/z 100 ion is obtained only from the cis-isomer. The [ C 6 H 14 N ] results of a collision-induced dissociation study are inconsistent with the previously proposed protonated dimethylaminocyclobutane structure (ion a) and suggest the N,N-dimethyl-1-butaneimmonium structure (ion b) for this ion. The mechanistic pathway proposed for this highly (CH 3 CH 2 CH 2 CHxN`(CH 3

) 2 ) stereospeciÐc process involves initial hydrogen migration from the hydroxy group to the radical site at the charged amino group as the stereospeciÐc step, this being possible only for the cis-amino alcohol. The EI mass spectra of the corresponding stereoisomeric methyl ethers exhibit preferential elimination of formaldehyde from the cis-isomer, which is explained by initial hydrogen migration from the methoxy group to the N atom. The unsubstituted cisand trans-1-methoxy-3-dimethylaminocyclohexanes do not show any stereospeciÐcity in their behavior under EI.

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