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Evaluation of nitric oxide chemical ionization mass spectra of substituted benzenes
Author(s) -
Daishima Shigeki,
Lida Yoshio,
Kanda Fujihiro
Publication year - 1991
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210260521
Subject(s) - substituent , chemistry , mass spectrum , toluene , ionization , medicinal chemistry , spectral line , electrophile , analytical chemistry (journal) , mass spectrometry , chemical ionization , ion , stereochemistry , organic chemistry , physics , chromatography , astronomy , catalysis
Nitric oxide chemical ionization mass spectra of substituted benzenes obtained with the Townsend discharge technique were studied. There were four kinds of base peaks in the mass spectra, i.e. [M + NO] + ˙, M + ˙, [M − H] + and [M − OR] + (R = H, CH 3 ). The formation of the specific ion [M + NO] + ˙ was highly dependent on the kind of substituent, and it was produced more abundantly in the case of substitutions involving electron‐accepting groups. The measure of [M + NO] + ˙ production was evaluated from the value of the ratio [M + NO] + ˙/M + ˙. In mono‐substitutions, it was clarified that the ratios of [M + NO] + ˙/M + ˙ were correlated with the Hammett substituent constant s̀ p or the electrophilic substituent constant s̀ p + . Monosubstitutions (C 6 H 5 R) and toluene substitutions (CH 3 C 6 H 4 R) could be classified into six groups in terms of base peak species, [M + NO] + ˙/M + ˙ ratios and substituents. In disubstitutions, the mass spectral patterns were governed by the combination of substituents. Mass spectral distinctions among ortho, meta and para isomers could be made in many cases.