Free radicals by mass spectrometry, XLVII. lonization potentials and ionic heats of formation of C5–C7 alkyl radicals

1976 ◽  
Vol 54 (6) ◽  
pp. 990-992 ◽  
Author(s):  
F. P. Lossing ◽  
Allan Maccoll
Keyword(s):  
Mass Spectrometry ◽  
Electron Beam ◽  
Free Radicals ◽  
Ionization Potentials ◽  
Heats Of Formation ◽  
Alkyl Radicals ◽  
Hydride Ion

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.

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

1972 ◽  
Vol 50 (24) ◽  
pp. 3973-3981 ◽  
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.

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

1971 ◽  
Vol 49 (3) ◽  
pp. 357-362 ◽  
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.

Free radicals by mass spectrometry. XLIL Ionization potentials and ionic heats of formation for C1—C4 alkyl radicals

1970 ◽  
Vol 48 (6) ◽  
pp. 955-965 ◽  
Author(s):  
F. P. Lossing ◽  
G. P. Semeluk
Keyword(s):  
Free Radicals ◽  
Excited States ◽  
Kinetic Data ◽  
Ionization Potentials ◽  
Heats Of Formation ◽  
Alkyl Radicals ◽  
Fragment Ions ◽  
Vibrational Levels ◽  
Upward Curvature ◽  
Linear Sections

Ionization potentials for C1—C4 alkyl free radicals have been re-measured by electron impact, using an energy-resolved electron beam from a double-hemispherical electrostatic monochromator. From these values and kinetic data for heats of formation of the radicals, ionic heats of formation for C1—C4 alkyl ions have been calculated. New values for the four isomeric butyl ions are given. The ionization efficiency curves for the simpler radicals show linear sections corresponding to excitation of vibrational levels; for larger radicals these segments are not resolved and only a smooth upward curvature is seen. In disagreement with earlier results, no evidence for formation of low-lying excited states of the ions could be found, either for parent or fragment ions.

Heats of formation of free radicals by mass spectrometry

1973 ◽  
Vol 95 (20) ◽  
pp. 6562-6566 ◽  
Author(s):  
D. K. Sen. Sharma ◽  
J. L. Franklin
Keyword(s):  
Mass Spectrometry ◽  
Free Radicals ◽  
Heats Of Formation

FREE RADICALS BY MASS SPECTROMETRY: X. THE IONIZATION POTENTIALS OF METHYL SUBSTITUTED ALLYL RADICALS

1956 ◽  
Vol 34 (3) ◽  
pp. 345-353 ◽  
Author(s):  
C. A. McDowell ◽  
F. P. Lossing ◽  
I. H. S. Henderson ◽  
J. B. Farmer
Keyword(s):  
Mass Spectrometry ◽  
Free Radicals ◽  
Electron Impact ◽  
Heat Of Formation ◽  
Ionization Potentials ◽  
Bond Dissociation Energies ◽  
Allyl Radical ◽  
Dissociation Energies ◽  
Allyl Halides ◽  
Vertical Ionization Potentials

The vertical ionization potentials of the β- and γ-methyl substituted allyl radicals as measured by electron impact are 8.03 ± 0.05 v. and 7.71 ± 0.05 v, respectively. From appearance potential data the following bond dissociation energies can be derived, assuming the dissociation processes to be free from complications:[Formula: see text]With assumptions about the structure of the ions produced by electron impact from the corresponding butenes the dissociation energies of the C4H7—H bonds in these latter compounds can be estimated, and the heats of formation of the corresponding radicals derived, namely:[Formula: see text]From data on the allyl halides we evaluate the heat of formation of the allyl radical to be:[Formula: see text]

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