Kinetic parameters and geometry of the transition state of decarboxylation reactions of carboxyl and formyl radicals

Experimental data on the degradation of carboxyl radicals RCO ₂ ^. → R^. + CO₂ (where R is an alkyl or aryl) and formyl radicals ROC^.O → R^. + CO₂ (where R is an alkyl or aryl) in the liquid phase were analyzed in terms of the method of crossing parabolas. The kinetic parameters that characterize this decomposition were calculated. Using the density functional theory, the transition state was calculated for the reaction of methyl radical addition to CO₂ at the C and O atoms. A semiempirical algorithm was developed for the calculation of the geometric parameters of the transition state for decomposition reactions of carboxyl and formyl radicals and the reverse addition reactions of R^. with CO₂. The kinetic (activation energies and rate constants) and geometric (interatomic distances in the transition state) reaction parameters were calculated for 37 degradation reactions of various formyl and carboxyl radicals. The activation energies and geometric parameters of the transition state were calculated for the alternative addition reactions of R^. to CO₂:R^. + CO₂ → RCO ₂ ^. (where R is an alkyl or aryl) and R^. + CO₂ → ROC^.O (where R is an alkyl or aryl). A linear correlation between the interatomic distance r ^#(C...C) (or r ^#(C...O)) in the transition state and the reaction enthalpy ΔH _e was found for the degradation reactions of carboxyl and formyl radicals (at br _e = const). The enthalpies, activation energies, and interatomic distances in the transition state for the degradation of carboxyl and formyl radicals and their formation were compared.     

An approach to evaluation of strength characteristics of rocks in boreholes

Conclusions  

Development of and experience using the Del’Tek computerized automation system for furnishing thermal power facilities with automated process control systems

Basic principles of constructing the Russian Del’Tek computerized automation system intended for development of modern process control systems for thermal power engineering facilities are considered. Informational-computation systems and full-scale process control systems built around the Del’Tek computerized automation system, as well as test results and experience gained from their operation, are described.     

Resolution of the Problem of Expanded Clay Rubble Dust Formation

Refractories and Industrial Ceramics - Sources of powdered waste in processing clay and other ceramic raw materials for crushing and screening complexes are crushers, screens, and transfer units. A...     

Tunneling transport through passivated CdS nanocrystal arrays grown by the Langmuir-Blodgett method

Tunneling electron transport through CdS nanocrystal arrays fabricated by the Langmuir-Blodgett method are studied by scanning electron spectroscopy. The effect of the matrix-annealing atmosphere on tunneling transport through the nanocrystal arrays is studied. Electron capture at traps in the case of nanocrystals annealed in vacuum is detected by tunneling current-voltage characteristics analyzed using a model relating the data of tunneling spectroscopy, photoluminescence, and quantum-mechanical calculation. Analysis shows that the nanocrystal surface is passivated by an ammonia monolayer upon annealing in an ammonia atmosphere. It is found that the substrate and surrounding non-passivated nanocrystals have an effect on the electron polarization energy.