scholarly journals FREE RADICALS BY MASS SPECTROMETRY: XXXIV. A FLOW REACTOR FOR MEASUREMENT OF FAST THERMAL REACTIONS

1966 ◽  
Vol 44 (18) ◽  
pp. 2205-2210 ◽  
Author(s):  
I. P. Fisher ◽  
J. B. Homer ◽  
B. Roberts ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Rate Constants ◽  
Flow Reactor ◽  
Residence Times ◽  
Thermal Reactions ◽  
New Type ◽  
Good Agreement ◽  
Gas Pressures

A new type of flow reactor for use with a mass spectrometer has been constructed, in which many of the disadvantages of flow systems for rate measurements have been overcome. Rate constants for unimolecular decompositions can be measured in the range 50 – 5 000 s−1, with helium carrier gas pressures of 10–50 mm and residence times of 10−3 to 10−1 s. Measurements of the rate of thermal decomposition of trioxane are in good agreement with the rates predicted from literature data obtained at much lower temperatures.

FREE RADICALS BY MASS SPECTROMETRY: VII. THE IONIZATION POTENTIALS OF ETHYL, ISOPROPYL, AND PROPARGYL RADICALS AND THE APPEARANCE POTENTIALS OF THE RADICAL IONS IN SOME DERIVATIVES

1955 ◽  
Vol 33 (5) ◽  
pp. 861-869 ◽  
Author(s):  
J. B. Farmer ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Kinetic Energy ◽  
Electron Impact ◽  
Ionization Potentials ◽  
Bond Dissociation Energies ◽  
Radical Ions ◽  
Dissociation Energies ◽  
Propargyl Radicals

The ionization potentials of ethyl, isopropyl, and propargyl radicals have been measured by electron impact on radicals produced by thermal decomposition of appropriate compounds. The values are:ethyl 8.78±0.05 ev., isopropyl 7.90±0.05 ev., and propargyl 8.25±0.08 ev. From the appearance potentials of these ions in various compounds, the following values of bond dissociation energies were obtained:[Formula: see text][Formula: see text] assuming no kinetic energy of the products.

FREE RADICALS BY MASS SPECTROMETRY: XXXII. THERMAL DECOMPOSITION OF CYCLOPENTYL RADICALS

1965 ◽  
Vol 43 (3) ◽  
pp. 565-569 ◽  
Author(s):  
T. F. Palmer ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Elevated Temperatures ◽  
Bond Rupture ◽  
Low Pressures

At low pressures and elevated temperatures cyclopentyl radicals are found to dissociate mainly by two modes of reaction: about 34% by loss of H atom to form cyclopentene, and about 66% by a C—C bond rupture to form ethylene and allyl radicals. Under the conditions employed no evidence for a third possible mode, the loss of H2 to form cyclopentenyl radical, could be found. It is estimated that an incidence of 2% of the latter could have been detected.

FREE RADICALS BY MASS SPECTROMETRY: XXXV. THE HEAT OF FORMATION OF ALLYL RADICAL FROM BIALLYL PYROLYSIS

1966 ◽  
Vol 44 (18) ◽  
pp. 2211-2217 ◽  
Author(s):  
J. B. Homer ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Thermal Decomposition ◽  
Total Pressure ◽  
Heat Of Formation ◽  
Kcal Mole ◽  
Allyl Radical ◽  
First Order ◽  
Secondary Reactions ◽  
Gas Pressures

The thermal decomposition of biallyl has been investigated from 977 – 1 070 °K at helium carrier gas pressures of 10–50 Torr. Under these conditions the rate of central C—C bond fission to give two allyl radicals can be measured without interference from secondary reactions. The reaction at the pressures employed is first order with respect to biallyl, but between first and second order in the total pressure. The temperature dependence of the rate constants, extrapolated to infinite pressure, and corrected to 298 °K, gives an activation energy of 45.7 kcal/mole for the reaction, corresponding to ΔHf(allyl) = 33.0 kcal/mole.

A Study of Ion—molecule Reactions in the Xe+ + Acetone System by Flow Technique Mass Spectrometry

2002 ◽  
Vol 8 (2) ◽  
pp. 147-156 ◽  
Author(s):  
P.S. Vinogradov ◽  
A.S. Misharin
Keyword(s):  
Mass Spectrometry ◽  
Rate Constants ◽  
Flow Reactor ◽  
Ionic Composition ◽  
Kinetic Scheme ◽  
Effective Rate ◽  
Fourth Generation ◽  
Buffer Gas ◽  
Acetone Concentration ◽  
Subsequent Transformation

Flow reactor technique mass spectrometry was used to study the reaction of Xe+ ions with acetone and the subsequent transformation of the product ions at a buffer gas (He) pressure of 1.1 Torr. A kinetic scheme describing the evolution of the ionic composition of the most abundant ionic constituents (up to the fourth generation) has been determined. The values of rate constants and branching ratios of the key reactions involved in the scheme have been evaluated from experimental kinetic dependences. The main channel of the Xe+ + acetone reaction (which occurs practically at each collision) is the production of the CH3CO+ fragment as the exothermicity of the charge transfer is higher than the dissociation threshold of the ground state acetone cation. The formation of a 2.5% fraction of the molecular ion via a parallel channel indicates that the production of an electronically-excited, long-lived state of the acetone cation takes place. The competition of association and particle-rearrangement processes in the reactions of the CH3CO+ ion and its CH3CO+(CH3)2CO cluster with acetone was also studied. It was found that channels in which a rearrangement of particles takes place (the production of protonated acetone for CH3CO+ and the protonated acetone dimer for CH3CO+(CH3)2CO) are slower than the association process at 1.1 Torr. Total effective rate constants (involving all the channels) for these ions are approximately several 10−10 cm3 s−1 units and the rate constant for the cluster ion is about 40% smaller. The production of slowly reacting C3H6O+ ions with an increase of acetone concentration was observed. Their structure may be ascribed to the enolic acetone cation (CH2COHCH3+). The only pathway for the loss of the ion in an exoergic reaction with acetone is the association process. The product of the process, i.e. the non-protonated ionic dimer of acetone, was also observed in the mass spectra.

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]

DISPROPORTIONATION AND RECOMBINATION OF CYANISOPROPYL RADICALS: REARRANGEMENT OF DIMETHYLKETENECYANISOPROPYLIMINE TO TETRAMETHYLSUCCINODINITRILE

1959 ◽  
Vol 37 (7) ◽  
pp. 1165-1169 ◽  
Author(s):  
M. Talât-Erben ◽  
A. N. Isfendiyaroğlu
Keyword(s):  
Experimental Data ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Molecular Mechanism ◽  
Reaction Scheme ◽  
Side Reactions ◽  
Minor Importance ◽  
Azo Compound ◽  
Kinetics Of ◽  
Good Agreement

Evidence is presented that the ketenimine intermediate formed in the thermal decomposition of azo-bis-isobutyronitrile (AIBN) rearranges quantitatively to tetramethylsuccinodinitrile (TMSDN), mainly by a molecular mechanism. Interpretation of experimental data on the basis of a reaction scheme consistent with the nature of the main products and the features of the kinetics of the decomposition permits estimation, by means of a simple diagram, of the extent of disproportionation, as well as that of the normal and abnormal recombination of cyanisopropyl radicals. The result obtained for the latter is in good agreement with that determined previously by an alternative method. The analysis does not exclude absolutely the possibility of side reactions in which the azo-compound partly decomposes by a molecular process, and the intermediate decomposes into free radicals. However, it is concluded that these side reactions, if any, must be of minor importance.

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.

Kinetics and mechanisms of the thermal decomposition of ethane - I. The uninhibited reaction

1961 ◽  
Vol 260 (1300) ◽  
pp. 91-102 ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Surface Area ◽  
Rate Constants ◽  
Time Course ◽  
Second Order ◽  
First Order ◽  
Elementary Steps ◽  
Good Agreement

The uninhibited ethane decomposition was studied from 550 to 640°C with the object of determining the overall mechanism. The reaction was found to be accurately of the first order at the higher pressures and lower temperatures employed, and to have an activation energy of 73·1 kcal under these conditions. The rate was decreased slightly by an increase in surface area, and the order was then somewhat greater than unity. At 640°C there was a transition to an order of 3/2 at a pressure of about 60 mm. Evidence is adduced in support of the conclusion that the initiating reaction is a second-order split of C 2 H 6 into 2CH 3 , as proposed by Küchler & Theile, and that the terminating step is C 2 H 5 + C 2 H 5 at the higher pressures and H + C 2 H 5 at the lower ones. The mechanism is shown to give a satisfactory interpretation of the time-course of the reaction, of the effects of adding ethylene and hydrogen, and of the effect of increasing the surface area. Calculated rates, using the rate constants for the elementary steps, are in good agreement with experiment.

scholarly journals Hydrogen Donors: Thermal Stabilizers for JP-8+100 at High Temperatures

1999 ◽  
Author(s):  
Edwin Corporan ◽  
Donald K. Minus
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
High Temperatures ◽  
Liquid Fuel ◽  
Flow Reactor ◽  
Gas Chromatography Mass Spectrometry ◽  
Conversion Rates ◽  
Hydrogen Donors ◽  
Exit Temperature ◽  
Gas Conversion

The effectiveness of hydrogen donor compounds as additives to reduce pyrolytic deposition in JP-8+100 at high temperatures was assessed. Decalin and 1,2,3,4 tetrahydroquinoline (THQ) were added to JP-8+100 at 0.5% (decalin only), 1.0 and 2.5% w/w concentrations and tested in a flow reactor at a fuel exit temperature of 600°C at 5.2 MPa. Measurements of carbon deposits along the tube and gas chromatography/mass spectrometry (GC/MS) analysis of the stressed and unstressed liquid fuel were used to assess effectiveness of the additive, and the degree of fuel decomposition. Additionally, liquid-to-gas conversion was determined, and the composition of the gas was determined via GC. Experimental results show significant reductions in pyrolytic deposition in JP-8+100 with the additives relative to the baseline fuel. Tests with decalin showed negligible effects on thermal oxidative deposits, while THQ produced significant increases in thermal oxidative deposits. The effects of the additives on fuel thermal decomposition and conversion rates are also discussed.

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