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An investigation of tautomeric equilibria by means of mass spectrometry
Author(s) -
Zamir Lolita,
Jensen Bror Skytte,
Larsen Elfinn
Publication year - 1969
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.1210020106
Subject(s) - tautomer , acetylacetone , chemistry , enol , ion , analytical chemistry (journal) , mass spectrum , mass spectrometry , inorganic chemistry , organic chemistry , catalysis , chromatography
Changes in the mass spectra with inlet temperature were used in this work to demonstrate the dependence of keto‐enol tautomerism of acetylacetone, 3‐methyl acetylacetone and 3‐allyl acetylacetone on temperature. The largest dependence of temperature were shown by the ion [M 42] +. arising from a McLafferty type rearrangement and by the ion [M Me] + resulting from simple α‐cleavage. The ion [M 42] +. peak increases with the temperature of the inlet system while the ion [M Me] + peak decreases. By assuming that the ion [M 42] +. represents the keto form and that the ion [M Me] + represents the cis‐enol form (stabilized by the hydrogen bond) one sees that the direction of the intensity variation of these peaks with temperature is in accord with the expected change of keto‐enol tautomerism with temperature. A quantitative correlation on the basis of the above assumptions is also approached. Recording of the mass spectra of these three β‐diketones at different energies of the incident electrons enables us to estimate whether or not the particular ions present in the mass spectra result from energetically favourable processes. The variation of the intensities of the peaks with the temperature of the inlet at different electron energies is also discussed.