Ionization-Dissociation of Some Cycloalkanes Under Electron Impact

Meyerson, Seymour; Nevitt, Thomas D.; Rylander, Paul N.

doi:10.1016/b978-0-08-009775-6.50032-3

Cited by 18 publications

(9 citation statements)

References 35 publications

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“…The El results of Stevenson3 and Meyerson et al 4 for methylcyclopentane-a-13C are quite consistent with the FIK results presented here. Stevenson found 52% retention of the labeled atom in C5H94" fragments, while Meyerson reported 42% retention.…”

Section: Discussionsupporting

confidence: 90%

“…One of these pathways apparently corresponds to the expected simple bond cleavage, but a significant fraction of the molecular ions must decompose by means of an intramolecular rearrangement followed by (or in concert with) bond scission. [4][5] The convincing evidence for the presence of competing modes of unimolecular decomposition strongly suggested to us that a kinetic study of the reactions involved would shed important new light on the details of these processes. The field-ionization kinetic (FIK) method6-7 which has been employed in the work reported here permits the study of unimolecular decomposition reactions of (radical) ions over a range of molecular-ion lifetimes extending from 10"11 to 10~5 sec.…”

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confidence: 95%

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Skeletal rearrangement of the methylcyclopentane ion. Field-ionization kinetic measurements

Falick¹,

Burlingame²

1975

J. Am. Chem. Soc.

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Section: Discussionsupporting

confidence: 90%

mentioning

confidence: 95%

Skeletal rearrangement of the methylcyclopentane ion. Field-ionization kinetic measurements

Falick¹,

Burlingame²

1975

J. Am. Chem. Soc.

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“…Fluorine-19 chemical shifts and coupling constants are often an order of magnitude larger than these parameters for a hydrogen nucleus in a similar situation and fluorine relaxa- sensitivity to detection nearly equivalent to and the observation that a covalently bound fluorine atom is nearly isosteric with covalent hydrogen,1 these facts have led to a burgeoning interest in the application of fluorine NMIÍ spectroscopy to biochemical systems.2 These experiments Can be classified according to whether the fluorine nucleus is covalently linked to the macromolecule under study3 or is attached to a small molecule which is in an equilibrium binding situation with the macromolecule. 4 A particularly interesting variant of the first type of experiment is the metabolic incorporation of fluorinated amino acids into proteins, providing multiple fluorine labeled materials for study.5-7 Consideration of the magnetic resonance properties of the macromolecule-associated form of fluorine nuclei follows the same theoretical principles in both types of experiments but the small molecule binding case is complicated by the presence of uncomplexed small molecules and the necessity to include in the discussion the rates at which equilibrium is maintained.…”

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confidence: 99%

Fluorine-proton Overhauser effects in fluorine-labeled macromolecular systems

Gerig¹

1977

J. Am. Chem. Soc.

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ions with three-, four-, and five-membered rings undergo ring opening after ca. 10-9 s to form initially 1-alkene molecular ions which, depending on the internal energy and ion lifetime, isomerize to some extent to a mixture of double bond isomers. From the identity of the CA spectra (reflecting to a large extent the stable ions) it can be concluded that the energy barrier for such ring opening processes is considerably smaller than the lowest threshold for decomposition and cannot exceed a few tenths of an electron volt.30In contrast, cycloalkane molecular ions with six-, seven-, and eight-membered rings are stable prior to decomposition over the entire range of lifetimes and internal energies available in an electron impact mass spectrometer. As already pointed out by Meyerson et al.4 for methylcyclopentane and methylcyclohexane the difference in the isomerization behavior is most simply accounted for as resulting from the difference in ring strain.Furthermore the present results rule out that threeor four-membered cycloalkane molecular ions are formed by 1,3or 1,4 elimination of HX from compounds of the general type RX (X = OH, F, Cl) as has been assumed sometimes in the past31 which does not exclude that these eliminations proceed via transition states with a cycloalkane-like structure.

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“…Cyclohexyl alkanes have also been reported on the basis of mass spectra of petroleum fractions [134] and in the Athabasca petroleum deposit [135]. An analysis of paraffin wax [111] indicated cyclopentyl-and cyclohexyl alkanes; this work, as well as that of MEYER-SON et al [136], also reports mass spectrometric results obtained for several authentic compounds of this class. More complex cyclic and bicyclic compounds have been isolated from petroleum.…”

Section: Cyclic Hydrocarbonsmentioning

confidence: 68%