Mechanism of thermal decomposition of dibenzhydryl oxalates

1967 ◽  
Vol 45 (24) ◽  
pp. 3035-3043 ◽  
Author(s):  
J. Warkentin ◽  
D. M. Singleton
Keyword(s):  
Thermal Decomposition ◽  
Transition State ◽  
High Temperatures ◽  
Diphenyl Ether ◽  
Isotope Effects ◽  
Slow Step ◽  
Radical Process ◽  
First Order ◽  
Mechanism Of Thermal Decomposition ◽  
O Isotope

Dibenzhydryl oxalate and several of its para-substituted analogs were thermally decomposed in diphenylmethane, diphenyl ether, and in α-chloronaphthalene solution. Evolution of gas (mainly CO2) was approximately first order, both rate and stoichiometry being poorly reproducible. Rates are correlated with σ+-substituent parameters, with ρ = −1.6 at 230.2°. The 13C/12C and 18O/16O isotope effects involved in CO2 formation were measured. It is concluded that thermolysis is a radical process with considerable polar character at the transition state and that the slow step involves concerted formation of one CO2 molecule, a diarylmethyl radical, and a carbodiarylmethoxy radical. The fate of the latter is primarily decarboxylation, but there is some decarbonylation and some trapping by diarylmethyl radicals. Tetraaryl ethane and CO2 are major products, the yield of the latter approaching 2 moles at high temperatures.

The thermal decomposition of t-alkyl N-arylcarbamates. I. The effect of ring substituents

1967 ◽  
Vol 45 (21) ◽  
pp. 2537-2546 ◽  
Author(s):  
M. P. Thorne
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Phenyl Ring ◽  
Diphenyl Ether ◽  
Decomposition Reaction ◽  
Aromatic Nucleus ◽  
Aryl Group ◽  
First Order ◽  
Cyclic Mechanism ◽  
Decomposition Increase

A series of t-butyl N-arylcarbamates in which the aryl group is a phenyl or a meta- or para-substituted phenyl ring has been prepared. Decomposition of these compounds in diphenyl ether at 177.5 °C has shown that the reaction is essentially first order, yielding carbon dioxide, isobutylene, and the corresponding amine. The rates of decomposition increase with increasing electronegativity of the substituent on the aromatic nucleus, and give a Hammett plot with a slope of 0.54. A cyclic mechanism is proposed for the decomposition reaction.

The thermal decomposition of 1-ethoxyethyl chloride and the reverse combination

1967 ◽  
Vol 20 (8) ◽  
pp. 1553 ◽  
Author(s):  
RL Failes ◽  
VR Stimson
Keyword(s):  
Thermal Decomposition ◽  
Transition State ◽  
Hydrogen Chloride ◽  
Ethyl Ether ◽  
Reverse Reaction ◽  
Kcal Mole ◽  
First Order ◽  
Polar Transition

1-Ethoxyethyl chloride decomposes cleanly at 164-221� into vinyl ethyl ether and hydrogen chloride in a first-order manner with k1 = 1010.52exp(-30300/RT) sec-1 (1) The equilibrium of the system at 128-221� approached from either direction at various pressures is well represented by (Kp in atmospheres) 1.987 In Kp = 31.1 � 0.9-(16500�500)/T (2) and this leads to ΔH�f,298(g) = -71.9 kcal mole-1 for 1-ethoxyethyl chloride. Combination of (1) and (2) gives k2 = 108.7exp(-14700/RT) sec-1 ml mole-1 for the reverse reaction and rate measurements verify this. The reactions are molecular, and relative rates indicate a polar transition state.

Thermal decomposition of alcohols. II. 2-Methylpropan-2-ol

1975 ◽  
Vol 28 (8) ◽  
pp. 1725 ◽  
Author(s):  
WD Johnson
Keyword(s):  
Thermal Decomposition ◽  
Free Radical ◽  
Arrhenius Equation ◽  
Initial Rate ◽  
Radical Mechanism ◽  
Reaction Products ◽  
Radical Process ◽  
First Order ◽  
Free Radical Mechanism

The thermal decomposition of 2-methylpropan-2-ol has been investigated from 503 to 612�C, over initial pressures ranging from 40 to 275 mm and in the presence of toluene from 520 to 602�C. The decomposition is homogeneous and first order with respect to the initial concentrations of alcohol giving the Arrhenius equation (R = 8.31 J mol-1 K-1) �������������������������� K=1012.7exp(-249,800/RT) s-1 for the initial rate. The decomposition of this alcohol is inhibited by the reaction products, mainly 2-methylpropene, and by the addition of toluene. There are contributions from the unimolecular elimination of water (k = 1013.6exp(-268,000/RT)s-1) and from a flee radical process (k = 1011.0 x exp(-227,000/RT) s-1). A free radical mechanism, which explains the minor products of the reaction and the varying results of other workers, is proposed.

Kinetics and mechanism of the thermal decomposition of N-nitrosodiphenylmethylimine

1981 ◽  
Vol 59 (3) ◽  
pp. 559-562 ◽  
Author(s):  
Michael T.H. Liu ◽  
Toshikazu Ibata
Keyword(s):  
Thermal Decomposition ◽  
Transition State ◽  
Experimental Evidence ◽  
Kinetics And Mechanism ◽  
Ring Closure ◽  
Decomposition Products ◽  
Cyclic Transition ◽  
First Order ◽  
Closure Mechanism ◽  
Cyclic Transition State

The thermal decomposition of N-nitrosodiphenylmethylimine has been investigated in various solvents. The decomposition products are benzophenone and nitrogen. The ΔH†and ΔS† parameters for these first-order decompositions have been determined. The experimental evidence is consistent with the hypothesis that the thermolysis of N-nitrosodiphenylmethylimine involves the formation of a cyclic transition state via an electrocyclic ring closure mechanism.

Thermal decomposition of formaldehyde at high temperatures

1985 ◽  
Vol 89 (14) ◽  
pp. 3109-3113 ◽  
Author(s):  
Ko Saito ◽  
Terumitsu Kakumoto ◽  
Yoshihiro Nakanishi ◽  
Akira Imamura
Keyword(s):  
Thermal Decomposition ◽  
High Temperatures
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