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Mass spectral study of O ‐ and S ‐aryl dimethylthiocarbamates under electron impact conditions: Newman‐Kwart rearrangement in the gas phase
Author(s) -
Prabhakar S.,
Kar Paramita,
Mirza S. P.,
Lakshmi V. V. S.,
Nagaiah K.,
Vairamani M.
Publication year - 2001
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/rcm.490
Subject(s) - chemistry , aryl , electron ionization , mass spectrum , fragmentation (computing) , substituent , polyatomic ion , moiety , ion , mass spectrometry , bond cleavage , medicinal chemistry , stereochemistry , crystallography , ionization , organic chemistry , catalysis , alkyl , chromatography , computer science , operating system
The electron impact (EI) mass spectra of isomeric S ‐ and O ‐aryl (2‐naphthyl, R‐Ph‐ = aryl, where R = H, NO 2 , COOCH 3 , COCH 3 and OCH 3 ) dimethylthiocarbamates have been studied in detail. The EI spectra of O ‐aryl dimethylthiocarbamates include some of the fragment ions that are characteristic of the corresponding S ‐aryl isomer, which could be explained by a Newman‐Kwart rearrangement in the ion source of the mass spectrometer, after ionization. The EI mass spectra of S ‐aryl dimethylthiocarbamates showed specific fragment ions resulting from cleavage of the molecular ion involving the bond between sulfur and the carbonyl group of the carbamate moiety (α‐cleavage). The EI mass spectra of O ‐aryl dimethylthiocarbamates, however, showed the fragmentation of the molecular ion by α‐cleavage involving the bonds on both sides of oxygen atom. Further, the EI mass spectra of O ‐aryl dimethylthiocarbamates containing an electron‐withdrawing substituent (‐R) on the aryl group showed a characteristic fragment ion corresponding to [M − R] + . Copyright © 2001 John Wiley & Sons, Ltd.