Molecular rearrangements. Part XX. Thermolysis of carboxylic acid esters

1983 ◽  
Vol 61 (7) ◽  
pp. 1532-1535 ◽  
Author(s):  
M. M. Aly ◽  
M. Z. A. Badr ◽  
A. M. Fahmy ◽  
S. A. Mahgoub
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Nitrogen Atmosphere ◽  
Radical Mechanism ◽  
Benzyl Benzoate ◽  
Phenyl Benzoate ◽  
Free Radical Mechanism ◽  
Homolytic Fission ◽  
Subsequent Decomposition ◽  
Acid Esters

Thermolysis of phenyl benzoate on heating under reflux for ca. 10 days in a nitrogen atmosphere gives phenol, o- and p-hydroxy biphenyl, biphenyl, and carbon monoxide. Phenyl phenylacetate under the same conditions gives toluene, bibenzyl, stilbene, phenol, o- and p-benzylphenol, 9-phenylxanthene, water, and carbon monoxide. Thermolysis of benzyl benzoate is accompanied by decarboxylation and the formation of toluene, diphenylmethane, bibenzyl, stilbene, and biphenyl. Thermolysis of benzyl phenylacetate proceeds smoothly, affording carbon dioxide, toluene, bibenzyl, and stilbene. It was concluded that thermolyses of esters proceeds through a free radical mechanism involving homolytic fission of either the O—CO or O–alkyl bond with subsequent decomposition of the radicals so formed.

Molecular rearrangements. Part XVI. Thermolysis and photolysis of N-benzyldiphenylamine and N-phenylacetyldiphenylamine

1980 ◽  
Vol 58 (12) ◽  
pp. 1229-1232 ◽  
Author(s):  
M. Z. A. Badr ◽  
M. M. Aly ◽  
A. M. Fahmy
Keyword(s):  
Carbon Monoxide ◽  
Free Radical ◽  
Radical Mechanism ◽  
Molecular Rearrangements ◽  
Free Radical Mechanism

Heating N-phenylacetyldiphenylamine in a sealed tube at 360 °C gave rise to carbon monoxide, bibenzyl, toluene, stilbene, diphenylmethane, aniline, carbazole, N-benzylcarbazole, acridine, 9-phenylacridine, 4-aminotriphenylmethane, diphenylamine, p-benzyldiphenylamine, and o-aminodiphenylmethane. A similar result was also obtained on heating N-benzyldiphenylamine, with the exception of carbon monoxide. Such results in addition to those obtained from photolysis of N-phenylacetyldiphenylamine are interpreted in terms of a free-radical mechanism.

scholarly journals Thermal decomposition of potassium titanium oxalate

2011 ◽  
Vol 76 (7) ◽  
pp. 1015-1026 ◽  
Author(s):  
Karuvanthodi Muraleedharan ◽  
Labeeb Pasha
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Model Fitting ◽  
Nitrogen Atmosphere ◽  
Single Step ◽  
Heating Rates ◽  
Decomposition Stage ◽  
Model Free ◽  
Good Agreement

The thermal decomposition of potassium titanium oxalate (PTO) was studied using non-isothermal thermogravimetry at different heating rates under a nitrogen atmosphere. The thermal decomposition of PTO proceeds mainly through five stages forming potassium titanate. The theoretical and experimental mass loss data are in good agreement for all stages of the thermal decomposition of PTO. The third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, were subjected to kinetic analyses both by the method of model fitting and by the model free approach, which is based on the isoconversional principle. The model free analyses showed that the combined elimination of carbon monoxide and carbon dioxide and formation of final titanate in the thermal decomposition of PTO proceeds through a single step with an activation energy value of about 315 kJ mol-1.

Methylene II. Gas phase reactions with ethyl chloride

1968 ◽  
Vol 306 (1485) ◽  
pp. 135-158 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Energy Content ◽  
Incident Light ◽  
Hydrogen Abstraction ◽  
Relative Concentration ◽  
Radical Mechanism ◽  
Gas Phase Reactions ◽  
Free Radical Mechanism ◽  
Singlet Methylene

In this work methylene was prepared by the photolysis of ketene, and the experiments include observations of the effects of changing the wavelength of the photolysing light and of introducing foreign gases. Results are consistent with a free-radical mechanism in which CH 2 abstracts a chlorine or a hydrogen atom from C 2 H 5 Cl: CH 2 +CH 3 CH 2 Cl→ k cl ĊH 2 Cl+CH 3 ĊH 2 , CH 2 +CH 3 CH 2 Cl→ k h1 ĊH 3 +ĊH 3 CH 3 Cl, } CH 2 +CH 3 CH 2 Cl→ k H2 ĊH 3 +CH 3 ċHCl. } ( k H ) All the fourteen products of the radical recombinations have been identified. Disproportionation of radicals and decomposition of excited molecules formed by recombinations yield additional products. Methylene insertion does not appear to play a significant role. When the incident light contains wavelengths in the region 2450 to 4000Å we find that k Cl / k H =1·62, k H1 / k H2 =0·098. If shorter wavelengths are excluded, or if nitrogen is added, lower values of k Cl / k H are obtained. On the other hand, in the presence of carbon monoxide the value of k Cl / k H may be greatly increased. It is suggested that these findings are attributable to differences in reactivity between singlet and triplet methylene. At longer wavelengths, or when nitrogen is present, the relative concentration of the singlet is reduced, but in the presence of carbon monoxide the triplet is removed preferentially (De Graff & Kistiakowsky 1967). Singlet methylene appears to be highly discriminating in its reactions, abstracting chlorine preferentially, while the triplet discriminates in favour of hydrogen abstraction. A kinetic analysis based on these ideas and consistent with the experimental observations shows that k S Cl / k S H >16·3, k T Cl / k T H <0·14. The selectivities shown by the two species of methylene are thought to be a result of differences in electronic structure rather than energy content.

PHOTOOXIDATION OF PROPIONALDEHYDE AT LOW PARTIAL PRESSURES OF ALDEHYDE

1966 ◽  
Vol 44 (24) ◽  
pp. 2973-2979 ◽  
Author(s):  
A. P. Altshuller ◽  
I. R. Cohen ◽  
T. C. Purcell
Keyword(s):  
Hydrogen Peroxide ◽  
Carbon Monoxide ◽  
Oxygen Molecule ◽  
Radical Mechanism ◽  
Alternative Mechanism ◽  
Alkyl Hydroperoxides ◽  
Free Radical Mechanism ◽  
Partial Pressures ◽  
Peroxy Acids ◽  
Radical Disproportionation

Propionaldehyde at partial pressures of from 0.0006 to 0.04 mm was photooxidized at 3 100 Å in the presence of 150 mm of oxygen. The major products were ethyl hydroperoxide and carbon monoxide. Acetaldehyde was formed at intermediate concentrations and formaldehyde, ethanol, methanol, hydrogen peroxide, and ethane were minor products. No ozone, peroxy acids, or diacyl peroxides could be detected.The results can be explained on the basis of a free-radical mechanism. Certain radical disproportionation reactions which are often postulated are unimportant because of the low partial pressures of propionaldehyde. An alternative mechanism involving direct chemical reaction of an oxygen molecule with the triplet state of the propionaldehyde may be of some significance, but cannot account for all of the products obtained. The present results indicate the importance of alkyl hydroperoxides as products in photooxidations at low partial pressures of aldehyde in the presence of large excesses of oxygen.

scholarly journals Controlled atmosphere GMAW welding of transportation vehicles and production machines parts made from 30MnB5 steel

2018 ◽  
Vol 216 ◽  
pp. 03001 ◽  
Author(s):  
Evgeny Ivanayskiy ◽  
Aleksei Ishkov ◽  
Aleksandr Ivanayskiy ◽  
Iakov Ochakovskii
Keyword(s):  
Mechanical Properties ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Chemical Composition ◽  
Controlled Atmosphere ◽  
Shielding Gas ◽  
Reducing Atmosphere ◽  
Metal Composition ◽  
Gmaw Welding ◽  
Welding Materials

The paper studies the influence of shielding gas on the composition and the structure of weld joint metal of 30MnB5 steel applied in essential parts of automobiles and tractors. The welding was performed in inert, oxidizing and reducing atmospheres. It was established that TIG welding with argon used as shielding gas did not provide the required mechanical properties when using conventional welding materials. Carbon dioxide during MAG welding caused partial burning of alloying elements. Carbon monoxide used as shielding gas was proved to form reducing atmosphere enabling to obtain chemical composition close to the base metal composition. Metallographic examinations were carried out. The obtained results provided full-strength weld, as well as the required reliability and durability of welded components and joints.

Comparative QSAR evidence for a free-radical mechanism of phenol-induced toxicity

2000 ◽  
Vol 127 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Corwin Hansch ◽  
Susan C. McKarns ◽  
Carr J. Smith ◽  
David J. Doolittle
Keyword(s):  
Free Radical ◽  
Radical Mechanism ◽  
Free Radical Mechanism
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