The Temperature Dependence of the Ratio kd/kc for Ethyl Radicals

1975 ◽  
Vol 53 (8) ◽  
pp. 1237-1244 ◽  
Author(s):  
D. G. Hooper ◽  
M. Simon ◽  
M. H. Back
Keyword(s):  
Liquid Phase ◽  
Transition State ◽  
Gas Phase ◽  
Rate Constants ◽  
Low Temperatures ◽  
Experimental Error ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
Temperature Range ◽  
Ethyl Radicals

The ratio of the rate constants for disproportionation and combination for ethyl radicals, kd/kc[Formula: see text]has been measured over the temperature range 298–173 K in the gas phase. Ethyl radicals were produced by direct photolysis of ethylene followed by addition of hydrogen atoms to ethylene. At low temperatures the only important reactions of the radicals were combination and disproportionation. The ratio kd/kc was obtained from measurements of the rates of formation of ethane, butane, and butene. No change in the ratio kd/kc was observed over the temperature range studied, leading to the conclusion that Ed − Ec = 0, within the experimental error. The significance of this result is discussed in relation to other measurements in both gas and liquid phase and to the nature of the transition state for this reaction.

60Co γ-RADIOLYSIS OF HYDROGEN HALIDES AT 77 °K

1966 ◽  
Vol 44 (2) ◽  
pp. 191-197
Author(s):  
R. C. Rumfeldt ◽  
D. A. Armstrong
Keyword(s):  
Liquid Phase ◽  
Hydrogen Atom ◽  
Experimental Error ◽  
Dose Dependence ◽  
Solid Matrix ◽  
Reactive Intermediate ◽  
Hydrogen Atoms ◽  
Hydrogen Halides ◽  
Atoms And Molecules ◽  
The Difference

Yields of hydrogen formed in the 60Co γ-radiolyses of pure polycrystalline samples of HBr and HCl at 77 °K decrease with increasing dose in the range 0 to 1 × 1018 eV per g. The true initial yields are G(H2)solidHClat77°K = 6.3 ± 0.2 and G(H2)solidHBrat77°K = 12.3 ± 0.3. Within experimental error these are the same as the respective liquid-phase yields at −79 °C. For doses in excess of 2 × 1018 eV per g the dose dependence is no longer significant and the yields tend toward plateau values of 3.2 ± 0.1 and 10.3 ± 0.1 for HCl and HBr respectively. The dose dependence of the hydrogen yields is attributed to the scavenging of a reactive intermediate by the halogen atoms and molecules which accumulate in the solid matrix as the dose increases.In independent experiments with an apparatus of the Klein–Scheer type it was shown that hydrogen atoms react readily with films of HBr at 77 °K. There is, however, no evidence of a significant reaction with HCl at this temperature. The difference in behavior of the two hydrogen halides may be explained by their different activation energies for reaction with hydrogen atoms. The results of the γ-radiolyses are discussed in the light of these experiments and it is suggested that the dose dependence may be a result of the scavenging of an ionic intermediate rather than a thermal hydrogen atom.

THE REACTION OF HYDROGEN AND DEUTERIUM ATOMS WITH PROPANE

1939 ◽  
Vol 17b (12) ◽  
pp. 371-384 ◽  
Author(s):  
E. W. R. Steacie ◽  
N. A. D. Parlee
Keyword(s):  
Activation Energy ◽  
High Temperatures ◽  
Low Temperatures ◽  
Hydrogen Atoms ◽  
Temperature Range ◽  
Secondary Reactions

The reaction of hydrogen atoms with propane has been investigated over the temperature range 30° to 250 °C. by the Wood-Bonhoeffer method. The products are solely methane at low temperatures, and methane, ethane, and ethylene at higher temperatures.It is concluded that the results can be explained only by the assumption that the reaction[Formula: see text]is of importance. The bearing of this on the Rice-Herzfeld mechanisms is discussed. The activation energy of the reaction is 10 ± 2 Kcal.The main steps in the postulated mechanism are:Primary Reaction[Formula: see text]Secondary Reactions at Low Temperatures[Formula: see text]Additional Secondary Reactions at High Temperatures[Formula: see text]The reaction of deuterium atoms with propane was also investigated. It was found that the methane and ethane produced were highly deuterized, while the propane was not appreciably exchanged.

Gas phase hydrolysis of sulfur tetrafluoride: A comparison of the gaseous and liquid phase rate constants

1985 ◽  
Vol 83 (5) ◽  
pp. 2618-2619 ◽  
Author(s):  
I. Sauers ◽  
J. L. Adcock ◽  
L. G. Christophorou ◽  
H. W. Ellis
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Rate Constants ◽  
Sulfur Tetrafluoride ◽  
Hydrolysis Of

Rate constants for the gas-phase reactions of cyclo-CXCXCF2CF2– (X=H, F) with OH radicals at a temperature range of 253–328K

2013 ◽  
Vol 572 ◽  
pp. 21-25 ◽  
Author(s):  
Xiaoqing Jia ◽  
Liang Chen ◽  
Junji Mizukado ◽  
Shuzo Kutsuna ◽  
Kazuaki Tokuhashi
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Oh Radicals ◽  
Gas Phase Reactions ◽  
Temperature Range

scholarly journals Pyrolysis of azetidinones. Part 2. Kinetics and mechanism of thermolysis of β-lactams and β-thiolactams

2016 ◽  
Vol 94 (9) ◽  
pp. 788-793 ◽  
Author(s):  
Nouf S. Al-Hamdan ◽  
Alya M. Al-Etaibi ◽  
Rasha F. Al-Bashir ◽  
Yahia A. Ibrahim ◽  
Nouria A. Al-Awadi ◽  
...  
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Kinetics And Mechanism ◽  
Energy Of Activation ◽  
The Novel ◽  
Temperature Range ◽  
Entropy Of Activation ◽  
Kinetics Of ◽  
Thermolysis Reaction

The kinetics of the gas-phase thermolysis reaction of seven β-lactams and their thione analogues were investigated over the temperature range 533–603 K for the β-lactams and 463–542 K for the β-thiolactams. The average values of the energy of activation (Ea) (kJ mol−1) and Arrhenius log A (s–1) were, respectively, 170.8 ± 18.6 and 12.4 ± 1.6 for the lactams and 131.7 ± 18.2 and 11.0 ± 2.0 for the thione analogues. The entropy of activation (ΔS#) was negative for of the substrates and slightly positive for three. The rate constants (k) (s−1) were calculated for 510 K and compared for the two series of azetidinones. The effects of substituents on rates and the novel role played by the C=O and C=S moieties on the relative reactivities of the cyclic amides are rationalized on the basis of a formal retro[2+2]cycloaddition mechanism used earlier to explain the products of the gas-phase thermolysis reaction of the present azetidinones.

scholarly journals THE REACTION OF HYDROGEN ATOMS WITH ISOBUTANE

1942 ◽  
Vol 20b (11) ◽  
pp. 255-264 ◽  
Author(s):  
W. Harold White ◽  
C. A. Winkler ◽  
B. J. Kenalty
Keyword(s):  
Activation Energy ◽  
Discharge Tube ◽  
Low Temperatures ◽  
Molecular Hydrogen ◽  
Methane Content ◽  
Hydrogen Atoms ◽  
Dehydrogenation Reaction ◽  
Temperature Range ◽  
Secondary Reactions

The reaction of hydrogen atoms with isobutane has been investigated by the Wood–Bonhoeffer discharge tube method, over a temperature range 30° to 250 °C. An activation energy of 10.5 ± 1.5 kcal. was obtained for the reaction.The nature of the products at a given temperature was found to depend upon the concentration of hydrogen atoms present. With low atom concentrations (5 to 9%) methane was essentially the only product at temperatures below 170 °C. At 250 °C., ethane was formed to the extent of approximately one-half the amount of methane. With higher atom concentrations (14 to 24%) ethane was formed in appreciable quantities at 140° to 170 °C., and exceeded the methane content at 250 °C. Small amounts of propane were formed at the higher temperatures.The results at low temperatures appear to be satisfactorily explained by assuming a primary dehydrogenation reaction:[Formula: see text]followed by a series of "atomic cracking" reactions. To account for the behaviour at higher temperatures, additional secondary reactions, involving decomposition of radicals and their reaction with molecular hydrogen, are assumed.

scholarly journals Predicting pressure-dependent unimolecular rate constants using variational transition state theory with multidimensional tunneling combined with system-specific quantum RRK theory: a definitive test for fluoroform dissociation

2016 ◽  
Vol 18 (25) ◽  
pp. 16659-16670 ◽  
Author(s):  
Junwei Lucas Bao ◽  
Xin Zhang ◽  
Donald G. Truhlar
Keyword(s):  
Experimental Data ◽  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Temperature Range ◽  
Multidimensional Tunneling ◽  
Specific Quantum ◽  
Wide Pressure

We show that rate constants for dissociation of fluoroform computed by VTST/SS-QRRK agree excellently with definitive experimental data over a wide pressure and temperature range.

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