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Electron‐impact induced skeletal re‐arrangement of 2‐methoxy‐3‐methylpyrazine and 2‐methylthio‐3‐methylpyrazine
Author(s) -
Kolor Michael G.,
Rizzo Donald J.
Publication year - 1971
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.1210050808
Subject(s) - fragmentation (computing) , chemistry , ion , metastability , polyatomic ion , mass spectrum , deuterium , molecule , crystallography , stereochemistry , medicinal chemistry , organic chemistry , physics , atomic physics , computer science , operating system
The mass spectra of 2‐methoxy‐3‐methylpyrazine (I), 2‐methoxy‐6‐methylpyrazine (II), 2‐methylthio‐3‐methylpyrazine (III) and 2‐methylthio‐6‐methylpyrazine (IV), are given and the major fragmentation pathways discussed. The novel loss of H 2 O from the molecular ion of I and the corresponding loss of H 2 S from the molecular ion of III indicate that a skeletal rearrangement takes place in the molecular ion preceding the expulsion of H 2 O and H 2 S. Proposed mechanisms for this behavior are discussed with evidence being drawn from accurate mass measurement, metastable ions, and deuterium and carbon‐13 labeling of the methoxy group. The absence of ions in the spectra of II and IV corresponding to the loss of H 2 O and H 2 S from these molecular ions clearly indicates that the position of the methyl group with respect to the methoxy group, or the methylthio group is in‐timately involved in this mechanism.