FREE RADICALS BY MASS SPECTROMETRY: XI. THE MERCURY PHOTOSENSITIZED DECOMPOSITION OF C2–C4 OLEFINS

1956 ◽  
Vol 34 (6) ◽  
pp. 701-715 ◽  
Author(s):  
F. P. Lossing ◽  
D. G. H. Marsden ◽  
J. B. Farmer
Keyword(s):  
Mass Spectrometry ◽  
Free Radicals ◽  
Hydrogen Atom ◽  
Mass Spectrometer ◽  
Cross Sections ◽  
Methyl Radicals ◽  
Allyl Radical

The mercury photosensitized (Hg3P1) decomposition of olefins has been examined using a reactor coupled directly to a mass spectrometer. The primary split of ethylene has been shown to be predominantly molecular, and that of propylene mainly into an allyl radical and a hydrogen atom. With 1-butene the split is predominantly at a C–C bond giving allyl and methyl radicals, although a rupture of a C–H bond occurs as well. With 2-butene and isobutene a C–H bond is broken. It is concluded that the allyl and methallyl radicals produced have large cross sections for reaction with excited mercury atoms.

FREE RADICALS BY MASS SPECTROMETRY: XIII. THE MERCURY PHOTOSENSITIZED DECOMPOSITION OF ALLENE AND BUTADIENE: THE C3H3 RADICAL

1957 ◽  
Vol 35 (8) ◽  
pp. 778-787 ◽  
Author(s):  
J. Collin ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Free Radicals ◽  
Hydrogen Atom ◽  
The Other ◽  
Methyl Radicals ◽  
Polymer Formation ◽  
Vinyl Radicals

The Hg(3P1) photosensitized decomposition of allene leads to the formation of a C3H3 radical. The reaction of this radical with added methyl radicals shows it to have the propargyl (ĊH2—C≡CH) structure rather than the alternative allenyl (CH2=C=ĊH) structure. The dissociation of 1,2-butadiene proceeds by two modes, one to give H2 + C4H4, and the other a split into CH3 and C3H3 radicals. The dissociation of 1,3-butadiene leads to the same final products, a shift of a hydrogen atom being required for the split into free radicals. No evidence was found for a dissociation of 1,3-butadiene into two vinyl radicals. Considerable polymer formation occurred with all three compounds.

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]

Free radicals by mass spectrometry. XL. Primary processes and transient intermediates in the mercury (3P1) photosensitization of hydrazine

1969 ◽  
Vol 47 (8) ◽  
pp. 1391-1393 ◽  
Author(s):  
A. Jones ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Free Radicals ◽  
Mass Spectrometer ◽  
Direct Evidence ◽  
Flow Reactor ◽  
Low Pressure ◽  
Primary Decomposition ◽  
Fast Flow ◽  
Transient Intermediates ◽  
Fast Flow Reactor

The low pressure mercury (3P1) photosensitized decomposition of hydrazine has been studied at 55 °C in a fast flow reactor coupled to a mass spectrometer. Direct evidence was obtained for the participation of N2H2, N2H3, NH2, and NH in the decomposition, and two primary decomposition modes were established[Formula: see text]

FREE RADICALS BY MASS SPECTROMETRY: III. RADICALS IN THE THERMAL DECOMPOSITION OF SOME BENZENE DERIVATIVES

1953 ◽  
Vol 31 (1) ◽  
pp. 30-41 ◽  
Author(s):  
K. U. Ingold ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Free Radical ◽  
Mass Spectrometer ◽  
Phenyl Ether ◽  
Benzyl Ether ◽  
Benzene Derivatives ◽  
Atomic Carbon ◽  
Benzene Toluene

The following benzene derivatives have been pyrolyzed in a free radical mass spectrometer: benzene, toluene, benzaldehyde, anisole, diphenyl, phenyl ether, and benzyl ether. The products and intermediates were analyzed, particular attention being paid to the formation (and stability) of any aromatic free radicals found. The phenyl, benzyl, phenoxy, and benzoyl radicals, as well as atomic carbon, were detected. The first two could be obtained abundantly and are fairly stable below 1150°. The oxygenated radicals were much less abundant and appeared to be less stable.

Some Novel Eliminations of Neutral Fragments from Ions in Mass Spectrometry

1966 ◽  
Vol 21 (5) ◽  
pp. 604-608 ◽  
Author(s):  
R. A. W. Johnstone ◽  
B. J. Millard
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrometer ◽  
Methyl Radicals

The loss of methyl radicals from diphenylmethyl, 1,2-diphenylethyl and stilbene ions in the mass spectrometer has been studied by means of 2H and 13C labelling. Mechanisms by which these methyl radicals are eliminated have been proposed.

FREE RADICALS BY MASS SPECTROMETRY: XII. PRIMARY STEPS IN THE MERCURY PHOTOSENSITIZED DECOMPOSITIONS OF ACETONE AND ACETALDEHYDE

1957 ◽  
Vol 35 (4) ◽  
pp. 305-314 ◽  
Author(s):  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Free Radicals ◽  
Hydrogen Atom ◽  
Mercury Atom ◽  
Secondary Reaction ◽  
Secondary Reactions ◽  
Tracer Experiments

The primary step in the mercury (Hg3P1) photosensitized decomposition of acetone at 55 °C. results in the formation of methyl and acetyl radicals. At least 25% of the acetyl radicals are sufficiently long-lived to suffer collision with a second excited mercury atom, the products being ketene and a hydrogen atom. The primary step in the decomposition of acetaldehyde is at least 95% to form methyl and formyl radicals. The methane found was shown by tracer experiments to be the product of a secondary reaction, probably that between methyl and formyl radicals. Other secondary reactions are discussed.

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