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Evidence for an ortho specific loss of OH· in some aromatic aldoximes from examination of metastable peak shapes
Author(s) -
Vijfhuizen Peter C.,
Terlouw Johan K.
Publication year - 1976
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.1210110815
Subject(s) - chemistry , protonation , metastability , ring (chemistry) , ion , deuterium , substituent , isocyanide , photochemistry , crystallography , stereochemistry , computational chemistry , organic chemistry , physics , quantum mechanics
The mechanism for loss of an OH radical from the molecular ions of the ortho substituted compounds 2‐methyl‐, 2‐hydroxy‐, 2‐amino‐ and 2‐methoxybenzaldoxime has been studied. It is inferred from the examination of the first field free region (composite) metastable peak shapes that two distinct mechanisms are operating. Based upon additional deuterium labelling experiments it is proposed that loss of OH involves both participation of the ortho substituent in the formation of a 5‐membered heterocyclic ring and the formation of a protonated isocyanide type ion via a 3‐membered ring transition state. Loss of OCH3 from the corresponding O‐methyl ethers probably occurs by similar mechanisms. The formation of a 5‐membered ring is also proposed to be the driving force for the loss of H2NO in the spectrum of 2‐methoxybenzaldoxime.