Stereospecificity of the Hofmann elimination in the gas phase. Issue 1 (February 2018)

• Record Type: Journal Article
• Authors: Figadére, Bruno; Cao, Tangyuan; Morton, Thomas H
• Is Part Of: European journal of mass spectrometry. Volume 24:Issue 1(2018)
• Page Start: 49
• Page End: 53
• Publication Date: 2018-02
• Subjects: Stereochemistry -- deuteration -- even-election ion -- fragmentation -- isotope effect; Mass spectrometry -- Periodicals; Mass Spectrometry; Mass spectrometry; Periodicals; Periodicals; 543.6505
• DOI: 10.1177/1469066717729536
• Languages: English
• ISSNs: 1469-0667

Abstract

The Hofmann elimination of ammonium ions having a single positive charge is demonstrated to exhibit stereospecificity with regard to expulsion of neutral alkene. For the 3-hexyl series of threo and erythro 4-monodeuterated ions (3-hexylammonium ion; N, N, N- trimethyl- d 3 -3-hexylammonium ion; N- ethyl-3-hexylammonium ion; N- methyl, N- ethyl-3-hexylammonium ion; N, N- dimethyl, N- ethyl-3-hexylammonium ion), the upper limit of the E:Z ratio of the expelled alkene (r) approaches 2 (the stereospecificity) with a deuterium isotope effect close to 2.0, although the effects of isotopic substitution diminish the E:Z ratio somewhat. Two fragmentations compete with that reaction: hydride shift (which gives the same products but with hydrogen scrambling) and loss of a neutral amine to give an alkyl cation. These competing reactions render our calculation approximate, but the results suggest a value not too far from the upper limit.