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Electron impact fragmentations of 1‐ and 3‐aryl‐3‐buten‐1‐ols
Author(s) -
Smith Grant Gill,
Voorhees Kent J.
Publication year - 1981
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.1210160206
Subject(s) - chemistry , aryl , fragmentation (computing) , substituent , allene , polyatomic ion , electron ionization , deuterium , medicinal chemistry , photochemistry , ion , organic chemistry , alkyl , physics , computer science , catalysis , ionization , operating system , quantum mechanics
Abstract The electron impact fragmentation of 1‐ and 3‐aryl‐3‐buten‐1‐ols show several distinguishing fragmentations. α‐Cleavage predominates in the fragmentation of the 1‐aryl‐3‐buten‐1‐ols to such an extent that molecular ions of only low intensity are observed. The ion resulting from α‐cleavage fragments readily with the loss of the ring substituent to the phenyl ion. An intense molecular ion is observed in the 3‐aryl series and a loss of 70 u is a major fragmentation in this series. Based on deuterium labeling studies, this unique fragmentation was explained by a hydroxylic hydrogen migration to the ring accompanied by the loss of allene and formaldehyde. Other major fragmentations observed in the 3‐aryl series are: a McLafferty‐type rearrangement (loss of formaldehyde), loss of 33 u (water + methyl radical), and the loss of 43 u (C 2 H 3 O and C 3 H 7 ). The proposed mechanisms have been substantiated by deuterium labeling and high resolution mass spectrometry. Substituent effects play a major role in the 3‐aryl series, but are insignificant in the 1‐aryl series.