Free-radical-catalyzed isomerization of isocyanides

1967 ◽  
Vol 45 (22) ◽  
pp. 2749-2754 ◽  
Author(s):  
D. H. Shaw ◽  
H. O. Pritchard
Keyword(s):  
Thermal Decomposition ◽  
Free Radical ◽  
Carbon Atom ◽  
Gas Phase ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Arrhenius Parameters ◽  
Reaction Proceeds ◽  
Methyl Isocyanide ◽  
Butyl Peroxide

The isomerization of methyl isocyanide and of ethyl isocyanide, catalyzed by methyl radicals produced in the thermal decomposition of di-tert-butyl peroxide, has been studied in the gas phase at temperatures near 100 °C. The Arrhenius parameters for the reaction CH3NC + CH3 → CH3 + CH3CN are E = 7.8 ± 0.3 kcal/mole and A = 1012.25 mole−1 cc s−1. It is proposed that the reaction proceeds by addition of the incoming radical to the divalent carbon atom of the isocyanide group, followed by expulsion of the radical originally attached to the N atom. The thermochemistry of addition to the divalent carbon atom is discussed in an Appendix.

THE GAS PHASE REACTION OF METHYL RADICALS WITH HEXAFLUOROACETONE

1957 ◽  
Vol 35 (10) ◽  
pp. 1216-1224 ◽  
Author(s):  
G. O. Pritchard ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Steric Factor ◽  
Phase Reaction ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Gas Phase Reaction

The photolytic and thermal decomposition of azomethane in the presence of hexafluoroacetone produces small amounts of fluorinated products, mainly fluoroform. The mechanism of this and related reactions is discussed. It is concluded that the proposed reaction.[Formula: see text]has an activation energy of about 6 kcal./mole, with a steric factor of about 10−5.

THE REACTION OF METHYL RADICALS WITH FORMALDEHYDE

1959 ◽  
Vol 37 (9) ◽  
pp. 1462-1468 ◽  
Author(s):  
A. R. Blake ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Addition Reactions ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
A Value ◽  
Abstraction Reaction ◽  
Butyl Peroxide

The pyrolysis of di-t-butyl peroxide has been reinvestigated and used as a source of methyl radicals to study the abstraction reaction between methyl radicals and formaldehyde. At low [HCHO]/[peroxide] ratios the system was simple enough for kinetic analysis, and a value of 6.6 kcal/mole was obtained for the activation energy. At higher [HCHO]/[peroxide] ratios the system became very complicated, possibly due to the increased importance of addition reactions.

The thermal decomposition of cyclobutane-1,2-dione

1985 ◽  
Vol 63 (11) ◽  
pp. 2945-2948 ◽  
Author(s):  
J.-R. Cao ◽  
R. A. Back
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Vapor Pressure ◽  
Gas Phase ◽  
Rate Constant ◽  
Surface Reaction ◽  
Order Rate Constant ◽  
Reaction Vessel ◽  
Arrhenius Parameters ◽  
First Order

The thermal decomposition of cyclobutane-1,2-dione has been studied in the gas phase at temperatures from 120 to 250 °C and pressures from 0.2 to 1.5 Torr. Products were C2H4 + 2CO, apparently formed in a simple unimolecular process. The first-order rate constant was strongly pressure dependent, and values of k∞ were obtained by extrapolation of plots of 1/k vs. 1/p to1/p = 0. Experiments in a packed reaction vessel showed that the reaction was enhanced by surface at the lower temperatures. Arrhenius parameters for k∞, corrected for surface reaction, were log A (s−1) = 15.07(±0.3) and E = 39.3(±2) kcal/mol. This activation energy seems too low for a biradical mechanism, and it is suggested that the decomposition is probably a concerted process. The vapor pressure of solid cyclobutane-1,2-dione was measured at temperatures from 22 to 62 °C and a heat of sublimation of 13.1 kcal/mol was estimated.

Di-tert-butyl peroxide decomposition behind shock waves

1976 ◽  
Vol 54 (4) ◽  
pp. 581-585 ◽  
Author(s):  
David K. Lewis
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Single Pulse ◽  
First Order ◽  
Tert Butyl ◽  
First Order Kinetics ◽  
Peroxide Decomposition ◽  
Butyl Peroxide ◽  
Temperature Work ◽  
Lower Temperature

The homogeneous, gas phase thermal decomposition of di-tert-butyl peroxide has been studied in a single pulse shock tube. Samples containing 0.05% to 0.5% reactant in argon were heated to 528–677 K at total pressures of about 1 atm. Acetone and ethane were the only significant products. The reaction obeyed first order kinetics. The Arrhenius parameters, log A (s−1) = 15.33 ± 0.50, Eact (kJ/mol) = 152.3 ± 5.8, are in agreement with the bulk of the earlier reported results of lower temperature work, and with a recently reported result obtained via the very low pressure pyrolysis technique. Indications from some of the earlier work that the A factor may decline at high temperatures are not supported by the present study.

THE REACTIVITY OF THE CYCLIC POLYENES TOWARDS FREE RADICALS: III. ADDITION OF THE ETHYL RADICAL

1965 ◽  
Vol 43 (5) ◽  
pp. 1110-1119 ◽  
Author(s):  
A. C. R. Brown ◽  
D. G. L. James
Keyword(s):  
Molecular Structure ◽  
Free Radicals ◽  
Gas Phase ◽  
Energy Of Activation ◽  
Kcal Mole ◽  
Arrhenius Parameters ◽  
Ethyl Radical ◽  
Cyclic Polyenes

Arrhenius parameters have been measured for the addition of the ethyl radical to cycloheptatriene-1,3,5 and to bicyclo[2.2.1]heptadiene-2,5 in the gas phase; the values for the energy of activation are distinct at 6.4 ± 0.2 and 7.0 ± 0.1 kcal/mole respectively. The addition of the ethyl radical to benzene, cyclohexadiene-1,4, and cyclooctadiene-1,5 proceeds too slowly to be detected. The significance of these results is considered in conjunction with those obtained previously for cyclohexadiene-1,3 and cyclooctatetraene, and the possibility of interpreting the reactivity of the cyclic polyenes in terms of molecular structure is discussed.

Hemolytic decomposition of di-sec-butyl peroxide

1970 ◽  
Vol 48 (4) ◽  
pp. 615-627 ◽  
Author(s):  
R. Hiatt ◽  
Sandor Szilagyi
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Hydrogen Production ◽  
Methyl Ethyl Ketone ◽  
Methyl Ethyl ◽  
Kcal Mole ◽  
Alkoxy Radicals ◽  
Solvent Cage ◽  
Butyl Peroxide

Rates and products have been determined for the thermal decomposition of sec-butyl peroxide at 110–150 °C in several solvents.The decomposition was shown to be unimolecular with energies of activation in toluene, benzene, and cyclohexane of 35.5 ± 1.0, 33.2 ± 1.0, 33.8 ± 1.0 kcal/mole respectively. The activation energy of thermal decomposition for the deuterated peroxide was found to be 37.2 + 1.0 kcal/mole in toluene.About 70–80% of the products could be explained by known reactions of free alkoxy radicals, and very little, if any, disproportionation of two sec-butoxy radicals in the solvent cage could be detected.The other 20–30% of the peroxide yielded H2 and methyl ethyl ketone. The yield of H2 was unaffected by the nature or the viscosity of the solvent, but H2 was not formed when s-Bu2O2 was photolyzed in toluene at 35 °C nor when the peroxide was thermally decomposed in the gas phase.α,α′-Dideutero-sec-butyl peroxide was prepared and decomposed in toluene at 110–150 °C. The yield of D2 was about the same as the yield of H2 from s-Bu2O2, but the rate of decomposition (at 135 °C) was only 1/1.55 as fast.Mechanisms for hydrogen production are discussed, but none satisfactorily explains all the evidence.

Isomerization of methyl isocyanide sensitized by vibrationally excited ethane

1969 ◽  
Vol 47 (4) ◽  
pp. 669-671
Author(s):  
D. H. Shaw ◽  
B. K. Dunning ◽  
H. O. Pritchard
Keyword(s):  
Free Radical ◽  
Total Pressure ◽  
The Other ◽  
Direct Transfer ◽  
Displacement Reaction ◽  
Methyl Radicals ◽  
Vibrationally Excited ◽  
Methyl Isocyanide

The isomerization of methyl isocyanide in the presence of methyl radicals takes place by two mechanisms. One is the simple free-radical displacement reaction which has been described previously. The other is through a direct transfer of energy from vibrationally excited ethane molecules. The vibrationally sensitized component can be quenched by increasing the total pressure.

THE THERMAL DECOMPOSITION OF METHYL HYDROPEROXIDE

1965 ◽  
Vol 43 (8) ◽  
pp. 2236-2242 ◽  
Author(s):  
Alexander D. Kirk
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constants ◽  
Dimethyl Phthalate ◽  
Kcal Mole ◽  
First Order ◽  
Methyl Hydroperoxide ◽  
Expected Values ◽  
Homogeneous Decomposition

The thermal decomposition of methyl hydroperoxide has been studied in solution and in the gas phase. The decomposition was found to be partly heterogeneous in solution in dimethyl phthalate and no reliable rate constants were obtained. Use of the toluene carrier method for the gas phase work enabled measurement of the rate constant for the homogeneous decomposition. The first order rate constants obtained range from 0.19 s−1 at 292 °C to 1.5 s−1 at 378 °C, leading to log A, 11± 2, and activation energy, 32 ± 5 kcal/mole. These results are compared with the expected values of log A, 13–14, and activation energy, 42 kcal/mole. The significance of these findings is discussed.

Pyrolysis of trifluoroacetaldehyde, initiated by di-tertiary-butyl peroxide decomposition

1979 ◽  
Vol 57 (17) ◽  
pp. 2201-2210 ◽  
Author(s):  
Leon F. Loucks ◽  
Michael T. H. Liu ◽  
David G. Hooper
Keyword(s):  
Thermal Decomposition ◽  
Decomposition Product ◽  
Reaction Order ◽  
Methyl Radicals ◽  
Reaction Products ◽  
Decomposition Products ◽  
Tertiary Butyl ◽  
Decomposition Reactions ◽  
Peroxide Decomposition ◽  
Butyl Peroxide

The thermal decomposition of 95:5 mixtures of trifluoroacetaldehyde (TFA) and di-tert-butyl peroxide (DTBP) has been studied at 100 Torr over the temperature range of 390 to 440 K. The major decomposition products included CO, CF3H, CH3COCH3, and CH4 while C2F6, CF3CHOHCH3, CF3CH3, CF3COCH3, C2H6, (CF3)2CHOH, and H2 were also found. In addition to the usual reactions for TFA thermal decomposition, reactions of methyl radicals with TFA to form isopropoxyl radicals were found. The alcohol products result from H atom abstraction reactions of the isopropoxyl radicals while CF3COCH3 is a decomposition product. Arrhenius parameters for several reactions were determined: for DTBP decomposition, log k = 15.82 − 37.73/2.303RT; for H abstraction from TFA by CH3, log k = 8.30 − 7.37/2.303RT; for H abstraction from TFA by CF3, log k = 8.98 − 8.61/2.303RT. Consideration has also been given to several rate constant ratios for the formation and decomposition of isopropoxyl radicals.A study of the reaction order for the formation of CF3H, C2F6, and CH4 showed that the orders were 3/2, 1, and 1 respectively for these three products. A reaction mechanism involving 14 individual steps is proposed to explain the reaction products and the observed orders of reaction.

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