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Quinoxalinol derivatives of aliphatic 2‐oxocarboxylic acids . Infrared and mass spectra of the O ‐trimethylsilylated compounds
Author(s) -
Langenbeck U.,
Möhring H. U.,
Hinney B.,
Spiteller M.
Publication year - 1977
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200040402
Subject(s) - chemistry , mass spectrometry , derivatization , mass spectrum , alkyl , pyridine , reagent , infrared spectroscopy , gas chromatography , ether , chromatography , ethylene , organic chemistry , medicinal chemistry , catalysis
In acidic media o ‐phenylenediamine and 2‐oxoacids react to yield quinoxaline derivatives. On derivatization in pyridine with silylating reagents quinoxalinol‐ O ‐TMS ethers or O ‐TMS‐ether‐TMS‐esters are formed exclusively as shown by gas chromatography infrared spectrometry and gas chromatography mass spectrometry. These derivatives have very favourable properties for gas chromatographic detection and quantitation of the parent 2‐oxoacids. The mass spectra have characteristic fragments which facilitate easy identification. In addition, ‘single ion monitoring’ of all aliphatic 2‐oxoacids can be performed with only three fragments at m / e 217, 232 and 245. In some aspects the mass spectra resemble those of other heterocyclic compounds which contain an O ‐alkyl sidechain. The fragmentation mechanisms were deduced by low resolution mass spectrometry with and without deuteration, high resolution mass spectrometry and metastable ion evidence. A new type of rearrangement α‐β‐elimination of ethylene or propylene from the aliphatic sidechain, is proposed for some O ‐TMS quinoxalinols.