ISSN:
0306-042X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
This study reports a rearrangement process observed in electron capture negative ion chemical ionization mass spectrometry of pentafluoropropionate and heptafluorobutyrate derivatives of some β-hydroxylated amines. The pentafluoropropionate derivatives of a number of these substituted amines yield a prominent anion of mass 145 (195 in the corresponding heptafluorobutyrate derivatives). In the pentafluoropropionate derivatives of ethanolamine and β-hydroxyphenethylamine this anion was quantitatively displaced to m/z 146 when the γ-hydrogen (relative to the derivatized hydroxyl group) was substituted by deuterium. We postulate an initial 6-membered transition state to produce a pentafluoropropionic acid anion (not observed) which then eliminates either a hydrogen atom to give m/z 163 or a fluorine atom to give m/z 145. The former remains at mass 163 in the γ-deuterated compounds examined. The proposed rearrangement is the negative ion analogue of the McLafferty rearrangement process of positive ion electron impact mass spectrometry. However, the negative ion rearrangement is not as general as its positive ion electron impact counterpart because the former is critically dependent upon the substitution present on the α and β carbon and nitrogen atoms, respectively, of the β-hydroxyamine-PFP (or HFB) derivatives. In this regard we examined the effects on m/z 145 anion formation of methyl substitution on the nitrogen and α and β carbon atoms of these pentafluoropropionate derivatives. The results suggest that electron capture methane negative ion chemical ionization mass spectra of β-hydroxylated PFP derivatives could be used as diagnostic tool for structural assignments within this group of compounds.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bms.1200110408
