Experimental and theoretical study of the enthalpy of formation of 3,6-diphenyl-1,2,4,5-tetroxane molecule.

We report the results obtained for the experimental determination and the theoretical calculation of the enthalpy of formation of 3,6-diphenyl-1,2,4,5-tetroxane molecule. The experimental work was performed using a macrocalorimeter to measure the combustion heat, and the sublimation enthalpy was determined via the measurement of the vapor pressure at equilibrium with the vapor phase at different temperatures resorting to the Clapeyron-Claussius equation. Theoretical calculations were performed using semiempirical AM1 and PM3 methods as well as ab initio techniques at the 3-21, 6-31G(d,p), and 6-311G(d,p) basis set levels.

Relationships between Kováts retention indices and molecular descriptors of 1-(2-hydroxy)-3-arylpropane-1,3-diones.

Experimental and theoretical results for retention index of a set of 20 beta-diketones are given. The quantitative structure-chromatographic retention relationships (QSRR) theory is employed and six molecular descriptors are chosen to compute the fitting polynomials. Multiple regression analysis yields satisfactory results when one resorts to several variables equations, instead of computing just one-variable formulae.

Kinetics and mechanism of gas-phase thermolysis using headspace-gas chromatographic analysis.

Headspace gas chromatography is employed in order to study the thermal decomposition reaction of gaseous di-tert-butyl peroxide (DTBP) in the 130 degrees C to 160 degrees C temperature range and in the presence of n-hexane as the internal standard and nitrogen as the carrier gas. The reaction exclusively yields acetone and ethane as products. First-order kinetics are observed, including when the surface-to-volume ratio (S/V) of the Pyrex 20-mL vial employed as the reactor is increased by packing it with silanized glass wool.

Characterization and carbon metabolism in fungi pathogenic to Triatoma infestans, a chagas disease vector.

The pathogenicity of Metarhizium anisopliae (Ma) and Beauveria bassiana (Bb) isolates against Triatoma infestans, the major vector of Chagas disease in Argentina is reported. A 100% mortality was achieved with mean lethal times varying form 5.8 (Ma6) to 7.