THE REACTION OF HYDROGEN ATOMS WITH METHYL CYANIDE

1955 ◽  
Vol 33 (12) ◽  
pp. 1814-1818 ◽  
Author(s):  
W. Forst ◽  
C. A. Winkler
Keyword(s):  
Discharge Tube ◽  
Hydrogen Cyanide ◽  
Main Product ◽  
Initial Step ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Cyanide ◽  
Secondary Reactions

Hydrogen atoms produced in a discharge tube were found to react with methyl cyanide to produce hydrogen cyanide as the main product, together with smaller amounts of methane and ethane. The proposed mechanism involves the formation of hydrogen cyanide and a methyl radical in the initial step; methane and ethane are attributed to secondary reactions of the methyl radicals.

Reactions of free radicals with aromatic compounds in the gaseous phase. I. Kinetics of the reaction of methyl radicals with toluene

1964 ◽  
Vol 17 (12) ◽  
pp. 1329 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams ◽  
JR Wilmshurst
Keyword(s):  
Flow System ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Benzyl Radical ◽  
Toluene Molecule ◽  
Benzyl Radicals ◽  
Butyl Peroxide ◽  
Kinetics Of

The kinetics of abstraction of hydrogen atoms from the methyl group of the toluene molecule by methyl radicals at 430-540�K have been determined. The methyl radicals were produced by pyrolysis of di-t-butyl peroxide in a stirred-flow system. The kinetics ,agree substantially with those obtained by previous authors using photolytic methods for generating the methyl radicals. At toluene and methyl-radical concentrations of about 5 x 10-7 and 10-11 mole cm-3 respectively the benzyl radicals resulting from the abstraction disappear almost entirely by combination with methyl radicals at the methylenic position. In this respect the benzyl radical behaves differently from the iso-electronic phenoxy radical, which previous work has shown to combine with a methyl radical mainly at ring positions. The investigation illustrates the application of stirred-flow technique to the study of the kinetics of free-radical reactions.

The reaction of hydrogen atoms with ethylene

1970 ◽  
Vol 316 (1527) ◽  
pp. 575-591 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Recombination Reaction ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Ethyl Radical ◽  
Cracking Reaction ◽  
Computer Calculations ◽  
First Time

A detailed study has been made of the products from the reaction between hydrogen atoms and ethylene in a discharge-flow system at 290 ± 3 K. Total pressures in the range 8 to 16 Torr (1100 to 2200 Nm -2 ) of argon were used and the hydrogen atom and ethylene flow rates were in the ranges 5 to 10 and 0 to 20 μ mol s -1 , respectively. In agreement with previous work, the main products are methane and ethane ( ~ 95%) together with small amounts of propane and n -butane, measurements of which are reported for the first time. A detailed mechanism leading to formation of all the products is proposed. It is shown that the predominant source of ethane is the recombination of two methyl radicals, the rate of recombination of a hydrogen atom with an ethyl radical being negligible in comparison with the alternative, cracking reaction which produces two methyl radicals. A set of rate constants for the elementary steps in this mechanism has been derived with the aid of computer calculations, which gives an excellent fit with the experimental results. In this set, the values of the rate constant for the addition of a hydrogen atom to ethylene are at the low end of the range of previously measured values but are shown to lead to a more reasonable value for the rate constant of the cracking reaction of a hydrogen atom with an ethyl radical. It is shown that the recombination reaction of a hydrogen atom with a methyl radical, the source of methane, is close to its third-order region.

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.

Reaction of methyl radicals with cis-butene-2

1969 ◽  
Vol 47 (16) ◽  
pp. 2987-3001 ◽  
Author(s):  
Nobuo Yokoyama ◽  
R. K. Brinton
Keyword(s):  
Gas Phase ◽  
Equilibrium Distribution ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Radical Concentration ◽  
Radical Decomposition ◽  
Similar Temperature ◽  
Carbonyl Radical

Methyl radicals generated by di-t-butylperoxide pyrolysis interact at comparable rates with cis-butene-2 in the gas phase by both addition and hydrogen atom abstraction. The determination of the rate of these reactions was simplified by the addition of a large concentration of acetaldehyde to the system. The additive, a source of low activation energy abstractable hydrogen atoms, was effective in suppressing polymerization reactions, and in addition, maintained a high steady state methyl radical concentration as a result of the carbonyl radical decomposition. The rate constants, k5 and k6 for the reactions [5] and [6], were determined to be 4.5 × 1010exp (−7000/RT)and 1.8 × 1010exp (−7300/RT)[Formula: see text]cm3 mole−1 s−1, respectively, over the temperature range 126–163 °C. The butenyl radical formed in reaction [6] isomerizes much faster than its interaction with other species in the system, and the distribution of the various conformations is similar to the equilibrium distribution of the butenes at a similar temperature.

THE REACTION OF ACTIVE NITROGEN WITH HYDRAZINE

1955 ◽  
Vol 33 (4) ◽  
pp. 692-698 ◽  
Author(s):  
G. R. Freeman ◽  
C. A. Winkler
Keyword(s):  
Hydrogen Cyanide ◽  
Chemical Reactivity ◽  
Large Contribution ◽  
Ammonia Production ◽  
Hydrogen Atoms ◽  
Active Nitrogen ◽  
Flow Rates ◽  
Production Of Hydrogen ◽  
Secondary Reactions ◽  
Excited Nitrogen

Hydrazine was completely destroyed by active nitrogen, at both 150 °C. and 480 °C., up to a hydrazine flow rate of about 22 × 10−6 mole per sec., whereas ammonia production was small at hydrazine flow rates below about 12 × 10−6 mole per sec. Thus it appears that ammonia is formed in secondary reactions only. The results indicate that NH2 radicals rather than hydrogen atoms may be prominent in secondary reactions. Comparison of the rate of hydrazine destruction with the rate of production of hydrogen cyanide from ethylene indicates that excited nitrogen molecules do not make a large contribution to the chemical reactivity of active nitrogen.

Abstraction of hydrogen atoms from bicyclo[2.1.1]hexane by methyl radicals and chlorine atoms: photochlorination of 1-methylbicyclo[2.1.1]hexane

1969 ◽  
Vol 47 (10) ◽  
pp. 1627-1631 ◽  
Author(s):  
R. Srinivasan ◽  
F. I. Sonntag
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Methyl Radicals ◽  
Absolute Rate ◽  
Methyl Radical ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Chlorine Atoms ◽  
Exponential Factor ◽  
Highly Strained

Photolysis of acetone has been used as a source of methyl radicals to study the abstraction of hydrogen atoms from bicyclo[2.1.1]hexane by methyl radicals. The reaction was found to have an activation energy of 10.3 kcal/mole and a pre-exponential factor that is typical of other abstraction reactions. The absolute rate of abstraction of hydrogen atoms from bicyclo[2.1.1]hexane by chlorine atoms at room temperature was measured to be 8.1 × 1010 l mole−1 s−1. The photochlorination of 1-methylbicyclo-[2.1.1]hexane in solution gave both the 1-chloromethyl and 2- or 3-chloro-1-methylbicyclohexanes. The relative rates of attack at the methyl and the 2- or 3- position were determined to be 1:2.1. It is pointed out that the rate parameters for the abstraction of an H atom from bicyclo[2.1.1]hexane by a methyl radical are slower than for cyclopentane, as would be expected for a highly strained hydrocarbon, whereas the abstraction by chlorine is slightly faster than the rate for cyclopentane.

The reaction of atomic hydrogen with methyl cyanide

1970 ◽  
Vol 48 (23) ◽  
pp. 3619-3622 ◽  
Author(s):  
J. W. S. Jamieson ◽  
G. R. Brown ◽  
J. S. Tanner
Keyword(s):  
Kinetic Parameters ◽  
Electric Discharge ◽  
Hydrogen Cyanide ◽  
Atomic Hydrogen ◽  
Hydrogen Atoms ◽  
Flow Rates ◽  
Methyl Cyanide ◽  
Different Temperatures ◽  
A Minor ◽  
Minor Extent

The reaction of hydrogen atoms, produced by electric discharge, with methyl cyanide vapor has been reinvestigated at seven different temperatures between 40 and 507 °C over a range of methyl cyanide flow rates from 2 to 25 μmoles/s. As in the previous limited investigation the products have been found to be hydrogen cyanide, methane, and ethane, but the present results indicate the presence of chain characteristics to a minor extent, propagated by CN. Kinetic parameters for formation of the products have been evaluated, as kHCN = 3.55 × 10−12 e−5816/RT; [Formula: see text]; and [Formula: see text].

THE REACTION OF ATOMIC HYDROGEN WITH FORMAMIDE VAPOR

1963 ◽  
Vol 41 (6) ◽  
pp. 1568-1574 ◽  
Author(s):  
J. W. S. Jamieson
Keyword(s):  
Thermal Decomposition ◽  
Free Radical ◽  
Reaction Temperature ◽  
Hydrogen Cyanide ◽  
Atomic Hydrogen ◽  
Main Product ◽  
Chain Mechanism ◽  
Hydrogen Atoms ◽  
Radical Chain ◽  
Wide Range

Hydrogen cyanide was the main product of the reaction of hydrogen atoms with formamide vapor; its rate of production was fairly rapid and completely independent of reaction temperature over a wide range. If a hydrogen is abstracted from formamide it must be one of the hydrogens bonded to nitrogen. The results of this investigation suggest the possibility of another free radical chain mechanism, which does not involve hydrogen atoms, for the thermal decomposition of formamide vapor.

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

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.

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