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Ion structural studies by ion kinetic energy spectrometry: [C 7 H 7 ] + , [C 7 H 8 ] + ˙, [C 7 H 7 OCH 3 ] + ˙
Author(s) -
Cooks R. G.,
Bey J. H.,
Bertrand M.,
Hoffman M. K.
Publication year - 1973
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.1210071110
Subject(s) - chemistry , cycloheptatriene , ether , ion , benzyl alcohol , polyatomic ion , protonation , benzyl bromide , photochemistry , medicinal chemistry , organic chemistry , catalysis
The use of kinetic energy release measurements in the structural characterization of ions formed in the mass spectrometer and in the determination of fragmentation mechanisms is demonstrated. In combination with information on the mode of energy partitioning in some of these reactions this allows the following conclusions: (i) The metastable [C 7 H 8 ] 8 ˙ ions formed from toluene, cyclohepatatriene, n ‐butylbenzene, the three methyl anisoles, methyl tropyl ether and benzyl methyl ether all undergo loss of H˙ from a common structure. (ii) The metastable [C 7 H 7 ] + ions generated from the same sources and from benzyl bromide, benzyl alcohol, p ‐xylene and ethylbenzene appear to undergo loss of acetylene from both the benzylic and the tropylium structures. (iii) The metastable [C 7 H 7 OCH 3 ] + ˙ ether molecular ions undergo loss of CH 3 ˙ by two types of mechanism, simple cleavage to give the aryloxy cation (not observed for benzyl methyl ether) and a rearrangement process which appears to lead to protonated tropone as the product. (iv) Loss of formaldehyde from the metastable [C 7 H 7 OCH 3 ] + ˙ molecular ions involves hydrogen transfer via competitive 4‐ and 5‐membered cyclic transition states in the case of the anisoles and in the case of methyl tropyl ether, while for benzyl methyl ether, hydrogen transfer in the nonisomerized molecular ion occurs via a 4‐membered cyclic transition state to yield the cycloheptatriene molecular ion.