Heats of formation of free radicals by mass spectrometry

Using an energy-resolved electron beam, ionization potentials have been measured for a number of C5–C7 isomeric alkyl radicals, produced by pyrolysis of nitrite intermediates. Values for primary radicals, which could not be produced in sufficient yield, are estimated by extrapolation from lower members of the series. Ionic heats of formation and hydride ion affinities are reported.

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Free Radicals by Mass Spectrometry. XLV. Ionization Potentials and Heats of Formation of C3H3, C3H5, and C4H7 Radicals and Ions

Canadian Journal of Chemistry ◽

10.1139/v72-629 ◽

1972 ◽

Vol 50 (24) ◽

pp. 3973-3981 ◽

Cited By ~ 181

Author(s):

F. P. Lossing

Keyword(s):

Mass Spectrometry ◽

Electron Beam ◽

Free Radicals ◽

Ionization Potentials ◽

Heats Of Formation ◽

Monoenergetic Electron ◽

Propargyl Radical ◽

Common Structure ◽

Fragment Ions ◽

Text Fragment

Using an energy-resolved electron beam, appearance potentials for[Formula: see text],[Formula: see text], and [Formula: see text] fragment ions from hydrocarbons of formula C3H4, C3H6, C4H6, C4H8, and C5H10 have been measured. In each case the fragment appears to have a common structure, corresponding to [Formula: see text], [Formula: see text], and [Formula: see text]. Ionization potentials have been measured for propargyl radical (8.68 V), methallyl radical (7.54 V), and 2-methylallyl radical (7.89 V). Corresponding ionic heats of formation are propargyl 281 ± 3 kcal/mol, methallyl 204 ± 3 kcal/mol, and 2-methylallyl 211 ± 5 kcal/mol. The [Formula: see text] fragment ion is 25 kcal/mol more stable than propargyl ion, and is almost certainly cyclopropenyl ion. Ionization potentials for propyne, allene, cyclopropene, 1- and 2-butyne, and fifteen isomers of formula CnH2n have also been measured by monoenergetic electron impact.

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Free Radicals by Mass Spectrometry. XLIII. Ionization Potentials and Ionic Heats of Formation for Vinyl, Allyl, and Benzyl Radicals

Canadian Journal of Chemistry ◽

10.1139/v71-060 ◽

1971 ◽

Vol 49 (3) ◽

pp. 357-362 ◽

Cited By ~ 123

Author(s):

F. P. Lossing

Keyword(s):

Mass Spectrometry ◽

Electron Beam ◽

Free Radicals ◽

Ionization Potentials ◽

Dissociative Ionization ◽

Heats Of Formation ◽

Neutral Radical ◽

Benzyl Radical ◽

Benzyl Cation ◽

Benzyl Radicals

Using an energy-resolved electron beam, ionization potentials for the following free radicals have been measured: vinyl 8.95 V, allyl 8.07 V, benzyl 7.27 V. For vinyl and allyl ions new measurements of thresholds for dissociative ionization give ΔHf(C2H3+) = 266 kcal/mol and ΔHf(C3H5+) = 226 kcal/mol, leading to neutral radical heats of formation ΔHf(C2H3) = 59.6 kcal/mol and ΔHf(C3H5) = 40 kcal/mol. The data for benzyl radical and ion give ΔHf(benzyl cation) = 213 kcal/mol.

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