The enthalpies of formation and reorganization of aromatic radicals

The enthalpies of formation of some biphenyl derivatives were determined. A "double difference" method for calculating the enthalpies of formation of aromatic radicals and the bond dissociation energies was proposed. The enthalpies of formation of the radicals biphenyl, diphenyl oxide, and phenyl oxide were determined. The energies of reorganization of these radicals as well as phenyl and 4-, 3-, and 2-pyridyls were calculated. The sums of the energies of the chemical bonds in the molecular moieties transformed into radicals upon the decomposition of chemical compounds were found to be constant for different compounds. The energies of the chemical bonds in arenes were determined.     

Energy characteristics of nitrooxazolidines and their radicals

Russian Chemical Bulletin - The standard molar enthalpies of combustion for three methyl and dimethyl nitrooxazolidine derivatives in the liquid and crystalline states were determined using a...     

Bond dissociation energies in nitramines

The enthalpies of formation in the standard state and in the gas phase were recommended for a series of secondary nitramines and n-butyldinitramine on the basis of the experimental enthalpies of combustion and vaporization and literature data. An analysis of the main thermochemical values (the enthalpies of formation in the gas phase and the enthalpies of atomization) showed that the energy properties of the nitramine group are independent of the structure of the molecules studied and of the number of functional groups in them. The enthalpies of formation of the alkylnitramine radicals were determined. The values obtained make it possible to calculate the bond dissociation energies in the nitramines and their radicals of different structures.     

Thermochemistry of complex salts of transition metal perchlorates with tetrazole ligands

The combined use of combustion and solution calorimetry was proposed as a method for determining the standard enthalpy of formation of the complex salts of transition metals, viz., cobalt(II), nickel(II), and zinc, with the organic ligand (5-aminotetrazol-1-yl)acethydrazide. The enthalpies of solution in water and in a 0.1 M solution of hydrochloric acid were measured for the complex salts and ligand. The enthalpy of combustion of the ligand was determined by the combustion calorimetry method, and its standard enthalpy of formation was calculated. The thermochemical cycle was developed for determining the standard enthalpy of formation of the complex salts. The reliable values of the enthalpies of formation of the salts in the standard states were obtained, and the enthalpies of formation of the earlier unknown complex ions were determined.     

Thermochemistry of complex salts of transition metal perchlorates with tetrazole ligands

Standard enthalpies of formation of transition metal (cobalt, nickel, and zinc) complex salts with an organic ligand 5-aminotetrazol-2-ylacetohydrazide (ATH-2) were obtained by combustion and solution calorimetry. The enthalpy of combustion of the ligand was determined using combustion calorimetry and the standard enthalpy of formation of the ligand was calculated. For calculations by reaction calorimetry, a thermochemical cycle was developed that allows determination of the standard enthalpy of formation of complex salts. The enthalpies of solution of the ligand and transition metal complex salts in water and in 0.1 M hydrochloric acid were determined. The data obtained allow calculations of the enthalpies of salts formation and the enthalpies of three new complex ions. The enthalpies of position isomerization in different compounds were analyzed.     

Experimental enthalpies of formation and other physicochemical characteristics of compounds containing C-NO2 and C-N(O)=N-NO2 groups: a comparison

Russian Chemical Bulletin - The standard enthalpies of formation of nitro-NNO-azoxy compounds including nitro-NNO-azoxybenzene (2), 3-nitro-4-{[4-(nitro-NNO-azoxy)furazan-3-yl]-NNO-azoxy}-furazan...     

Simulation and study of stratified flows around finite bodies

The flows past a sphere and a square cylinder of diameter d moving horizontally at the velocity U in a linearly density-stratified viscous incompressible fluid are studied. The flows are described by the Navier–Stokes equations in the Boussinesq approximation. Variations in the spatial vortex structure of the flows are analyzed in detail in a wide range of dimensionless parameters (such as the Reynolds number Re = Ud/ν and the internal Froude number Fr = U/(Nd), where ν is the kinematic viscosity and N is the buoyancy frequency) by applying mathematical simulation (on supercomputers of Joint Supercomputer Center of the Russian Academy of Sciences) and three-dimensional flow visualization. At 0.005 < Fr < 100, the classification of flow regimes for the sphere (for 1 < Re < 500) and for the cylinder (for 1 < Re < 200) is improved. At Fr = 0 (i.e., at U = 0), the problem of diffusion-induced flow past a sphere leading to the formation of horizontal density layers near the sphere’s upper and lower poles is considered. At Fr = 0.1 and Re = 50, the formation of a steady flow past a square cylinder with wavy hanging density layers in the wake is studied in detail.