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Hydrogen migrations in mass spectrometry. I—The loss of olefin from phenyl‐ n ‐propyl ether following electron impact ionization and chemical ionization
Author(s) -
Benoit Frank M.,
Harrison Alex G.
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.1210110606
Subject(s) - chemistry , electron ionization , chemical ionization , ionization , ether , protonation , hydrogen , molecule , photochemistry , olefin fiber , mass spectrometry , alkyl , electron transfer , ion , medicinal chemistry , organic chemistry , catalysis , chromatography
Using specifically labelled compounds we have made a detailed study of the source of the hydrogen transferred in the elimination of C 3 H 6 from the molecular ion of phenyl n ‐propyl ether following electron impact ionization and from the protonated (and ethylated) molecule following chemical ionization. The migrating hydrogen originates from all three positions of the n propyl group but not in the ratio expected for randomization of the alkyl hydrogens prior to transfer. The source of the migrating hydrogen is similar for both electron impact ionization and chemical ionization, indicating that the factors governing the rearrangement are the same for both modes of ionization. From a comparison of the results for labelled 2,6‐dimethyl phenyl n ‐propyl ethers with the results for the unsubstituted ether it is concluded that hydrogen transfer occurs only to the ether oxygen and not to the phenyl ring. A two‐step mechanism involving a set of competing reversible hydrogen transfer reactions followed by CO bond cleavage is proposed to explain the results.