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.

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 nitrous oxide II. Influence of added gases and a theory of the kinetic mechanism

1955 ◽  
Vol 231 (1185) ◽  
pp. 178-197 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Nitrous Oxide ◽  
Initial Pressure ◽  
Kinetic Mechanism ◽  
Gas Pressure ◽  
Unimolecular Reactions ◽  
Chemical Decomposition ◽  
First Order ◽  
Decomposition Of Nitrous Oxide

The influence of foreign gas additions (argon, nitrogen, carbon dioxide, carbontetrafluoride and mixtures of them) on the thermal decomposition of nitrous oxide at a series of different initial pressures has been studied. The curves of k , the formal first-order constant, as a function of x , the foreign-gas pressure, show regions of rapidly falling slope analogous to those found in the curves of k against n , the initial pressure of nitrous oxide. The forms of the curves have been investigated in some detail, and suggest very strongly the existence of potentially rate-determining processes other than those normally assumed in unimolecular reactions (which are energization of molecules in collisions and chemical decomposition of these molecules). It is now postulated that spontaneous and collision-induced transfers of energized nitrous oxide molecules to trip let states constitute the processes in question, and on this basis the forms of the k , n and k , x curves are interpreted. This postulate links up with certain spectroscopic considerations previously advanced by Herzberg.

Thermal decomposition of citraconic anhydride

1971 ◽  
Vol 24 (4) ◽  
pp. 771 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constant ◽  
Arrhenius Equation ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
First Order Kinetics ◽  
Citraconic Anhydride

Citraconic anhydride decomposes in the gas phase over the range 440- 490� to give carbon dioxide, carbon monoxide, and propyne which undergoes some polymerization to trimethylbenzenes. The decomposition obeys first-order kinetics, and the Arrhenius equation ������������������� k1 = 1015.64 exp(-64233�500/RT) (s-1) describes the variation of rate constant with temperature. The rate constant is unaffected by the addition of isobutene or by increase in the surface/volume ratio of the reaction vessel. The reaction appears to be unimolecular and if a diradical intermediate is involved it may not be fully formed in the transition state.

Mechanism of SNi reactions. The effect of the base strength of the anionic fragments

1978 ◽  
Vol 56 (19) ◽  
pp. 2582-2589 ◽  
Author(s):  
D. J. Verrinder ◽  
M. J. Hourigan ◽  
J. M. Prokipcak
Keyword(s):  
Thermal Decomposition ◽  
Optical Activity ◽  
Ion Pair ◽  
Decomposition Rates ◽  
First Order ◽  
First Order Kinetics ◽  
Cyclic Mechanism ◽  
Base Strength ◽  
Oxygen Bond ◽  
Anionic Fragment

The kinetics and stereochemical aspects of the thermal decomposition of aralkyl carbonates, thiocarbonates, and carbamates were examined. The rates for the decompositions as well as the rates of loss of optical activity followed first-order kinetics. The decompositions appear to involve the heterolysis of the aralkyl–oxygen bond followed by the breakdown of the subsequent ion pair via a cyclic mechanism. However, it was found that this ion pair could return to covalency without completely decomposing to products leading to the racemization of the starting materials. This type of racemization occurred more readily in the case of the carbamates than in the thiocarbonates and carbonates. The dependence of the decomposition rates and the loss of optical activity on the nature of the hetero atom of the anionic fragment of the starting material is discussed.

Thermal decomposition of di-tert-butyl peroxide at high pressure

1968 ◽  
Vol 46 (16) ◽  
pp. 2721-2724 ◽  
Author(s):  
D. H. Shaw ◽  
H. O. Pritchard
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
High Pressure ◽  
Shock Tube ◽  
Total Pressure ◽  
Order Rate Constant ◽  
Kcal Mole ◽  
First Order ◽  
Tert Butyl ◽  
Butyl Peroxide

The thermal decomposition of di-tert-butyl peroxide has been studied in the presence of carbon dioxide at total pressures from 0.05 to 15 atm and temperatures from 90–130 °C. The first-order rate constant for the decomposition is independent of total pressure in this range, with Arrhenius parameters E = 37.8 ± 0.3 kcal/mole and log A(s−1) = 15.8+0.2. A reevaluation of previous data on this reaction leads us to recommend E = 37.78 ± 0.06 kcal/mole and log A(s−1) = 15.80 ± 0.03 over the temperature range 90–350 °C; extension of this range to higher temperatures using a shock tube would be worthwhile.

scholarly journals Thermal decomposition of 3,6-diphenyl-1,2,4,5-tetroxane in nitromethane solution

2018 ◽  
Vol 15 (2) ◽  
pp. 6306-6310
Author(s):  
Nelly Lidia Jorge ◽  
Alexander German Bordón ◽  
Andrea Natalia Pila ◽  
Mariela Ines Profeta ◽  
Maria Josefa Jorge ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Benzoic Acid ◽  
Activation Enthalpy ◽  
Decomposition Reaction ◽  
Activation Entropy ◽  
Order Kinetic ◽  
Stepwise Mechanism ◽  
First Order ◽  
Mechanism Of Decomposition ◽  
Organic Products

The thermal decomposition reaction of benzaldehyde diperoxide (DFT; 0.001 mol L-1) in nitromethane solution studied in the temperature range of 130.0-166.0 °C, follows a first-order kinetic law up to at least 60% DFT conversion. The organic products observed were benzaldheyde and benzoic acid. A stepwise mechanism of decomposition was proposed where the first step is the homolytic unimolecular rupture of the O-O bond. The activation enthalpy and activation entropy for DFT in nitromethane were calculated (DH# = 106.3 ± 1.0 kJ mol-1 and DS# = -58.6 ± 1.1 J mol-1K-1) and compared with those obtained in other solvents to evaluate the solvent effect.

THE THERMAL DECOMPOSITION OF PHENYLACETIC ACID

1960 ◽  
Vol 38 (8) ◽  
pp. 1261-1270 ◽  
Author(s):  
Margaret H. Back ◽  
A. H. Sehon
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Rate Constant ◽  
Phenylacetic Acid ◽  
Order Process ◽  
First Order ◽  
Kinetics Of ◽  
Dissociation Step

The thermal decomposition of phenylacetic acid was investigated by the toluene-carrier technique over the temperature range 587 to 722 °C. The products of the pyrolysis were carbon dioxide, carbon monoxide, hydrogen, methane, dibenzyl, and phenylketene. From the kinetics of the decomposition it was concluded that the reaction[Formula: see text]was a homogeneous, first-order process and that the rate constant of this dissociation step was represented by the expression k = 8 × 1012.e−55,000/RT sec−1. The activation energy of this reaction may be identified with D(C6H5CH2—COOH). The possible reactions of carboxyl radicals are discussed.

Mono, Di and Trifunctional Cyclic Organic Peroxides: The Effect of Substituents and Ring Size on their Thermolysis in 1,4-dioxan

2013 ◽  
Vol 66 (9) ◽  
pp. 1080 ◽  
Author(s):  
Rosa Nesprias ◽  
Gladys Eyler ◽  
Adriana Cañizo
Keyword(s):  
Thermal Decomposition ◽  
Statistical Treatment ◽  
Activation Parameters ◽  
Decomposition Reaction ◽  
Order Kinetic ◽  
Organic Peroxides ◽  
Solvent Interaction ◽  
Kinetic Behaviour ◽  
First Order ◽  
Thermal Stability Of

The thermal decomposition reaction of cyclic organic peroxides was studied in 1,4-dioxan at initial concentrations between ~10–4 and 10–2 mol L–1 and at a temperature interval between 100 and 170°C, according to the thermal stability of each compound. The kinetic behaviour observed in all systems studied follows a pseudo first order kinetic law up to at least ~86 % of peroxide conversion. An important substituent effect is operative on the rate constant values and consequently on the activation parameters of the thermal decomposition reaction. The application of different treatments (compensation affect or a statistical treatment) on the kinetic data shows the existence of two sets of cyclic peroxides with comparable kinetic behaviour. Different peroxide–solvent interaction mechanisms can be considered within each series.

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