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The [M−H−CO 2 ] − anion from glycyl glycine undergoes rearrangement in the gas phase
Author(s) -
Styles Michelle L.,
O’Hair Richard A. J.
Publication year - 1998
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19980715)12:13<809::aid-rcm238>3.0.co;2-x
Subject(s) - chemistry , rearrangement reaction , carbanion , ion , intramolecular force , fragmentation (computing) , transition state , glycine , gas phase , ab initio , nitrogen , medicinal chemistry , computational chemistry , stereochemistry , organic chemistry , amino acid , catalysis , biochemistry , computer science , operating system
The [M−H−CO 2 ] − anion derived from collision induced loss of CO 2 from the [M−H] − ion of glycyl glycine has been examined using various tandem mass spectrometry (MS/MS) experiments. Using 15 N isotopically labelled glycyl glycine, these MS/MS experiments reveal that the initially formed carbanion [H 2 NCH 2 C(O)NHCH 2 ] − ( A ) undergoes rearrangement to the nitrogen anion [HNCH 2 C(O)NHCH 3 ] − ( B ). The latter ion is responsible for the subsequent fragmentation reactions. In addition, high level ab initio calculations (at the MP2/6‐31+G * level of theory) have been carried out on the rearrangement of A to B , which reveal that this intramolecular rearrangement process proceeds via a six centred transition state with a modest activation energy (11.1 kcal mol −1 ) and is overall exothermic by 3.2 kcal mol −1 thereby favouring the formation of the product B . © 1998 John Wiley & Sons, Ltd.