Lázaro F. R. Cafferata

Improved procedure for the preparation of diethyl ketone triperoxide and kinetics of its thermal decomposition reaction in solution

Abstract Diethyl ketone triperoxide is obtained in a simple and efficient one-step procedure using the acid-catalysed oxidation reaction of diethyl ketone by hydrogen peroxide. Its thermolysis in toluene solution is initiated by a rate determining peroxidic bond rupture of that substituted triperoxane molecule.

Experimental and theoretical study of trans-3,6-diphenyl 1,2,4,5-tetroxane molecule

Abstract An experimental and theoretical study of trans -3,6-diphenyl-1,2,4,5-tetroxane molecule is presented comparing the data with the cis -isomer calculations. The different electronic and steric factors which determine the most stable molecular configurations are discussed through semi-empirical AM1 and PM3 methods to obtain the lowest energy conformers and the most characteristic geometrical parameters of the molecule. The results are discussed considering the 1 H NMR spectrum data obtained for the title compound.

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.

Ameliorate QSPR Study of Alkyl Hydroperoxides

A set of linear and nonlinear functions of one and several variables are determined to predict refractive index, molar refraction, and density for a representative set of alkyl hydroperoxides. Quite satisfactory predictions can be made on the basis of these equations and in some cases it is necessary to resort to higher-order equations to get a very good quantitative description of physical properties. Some possible further extensions of this study are pointed out in order to get a step head in the understanding of the quan- titative structure-property relationships of alkyl hydroperoxides.

Solvent and Substituent Effects on the Kinetics of Thermolysis of cis-Fused 1,2,4-Trioxanes

The kinetics of the thermal decomposition reaction of cis-6-phenyl-5,6-(2-phenylpropyliden)-3,3-pentamethylene-1,2,4-trioxacyclohexane (Ia) were investigated in benzene and methanol solutions in the temperature and concentration ranges of 353.3 – 413.2 K and (1.1 – 13.1)x10-3 M, respectively. First-order rate constant values were obtained for up to at least ca. 20% conversions of that cyclic peroxide. The activation parameter values for the initial unimolecular homolysis of that molecule, results supported by the effect of the addition of di-tert-butyl-p-cresol as a free radical scavenger, indicate a stepwise reaction mechanism which is in keeping with the reaction products analysis. The corresponding activation parameters for the reaction of Ia in methanol (ΔH# = 20.2 ± 0.6 kcal mol-1; ΔS# = 0.1 ± 1.6 cal mol-1 K-1; ΔG# = 20.2 ± 0.6 kcal mol-1) and in benzene (ΔH# = 15.4 ± 0.2 kcal mol-1; ΔS# = -13.2 ± 0.5 cal mol-1 K-1; ΔG# = 20.5 ± 0.2 kcal mol-1) solutions are compared with values obtained for cis-6-phenyl-5,6-(2-phenylpropyliden)-3,3-tetramethylene-1,2,4-trioxacyclohexane (Ib) thermolysis in the same solvents. The thermolysis kinetics of Ia are less sensitive to solvent changes compared to the behaviour already reported for the analogous reactions of Ib. Because both molecules in solution are flexible structures due to their configurations, the relatively small solvent effect found on the former trioxane reaction is attributed to the extent of the chain of methylene groups attached on C-3 of the corresponding molecular rings. Furthermore, the pertinent substituent effect on the peroxidic bond strength of those molecules in solution was evaluated.

THEORETICAL STUDY OF CIS- AND TRANS-3,6-DIMETHOXY-1,2,4,5-TETROXANE MOLECULE

Abstract Results of a theoretical study of cis- and trans -3,6-dimethoxy-1,2,4,5-tetroxane molecules are presented. The different electronic and steric factors which determine the most stable molecular configurations are discussed. We resort to the semiempirical AM1 and PM3 methods to obtain the lowest energy isomers and the most characteristic geometrical parameters for them are given.

Solvent and Substituent Effects on the Thermolysis of Antimalarial Fluorophenyl Substituted 1,2.4-Trioxanes

The kinetics and mechanism of the thermal decomposition reaction of cis-6-(4-fluoropheny1)-5,6-[2-(4-fluorophenyl)-propylidene]-3,3-tetramethylene-l,2,4-trioxacyclo-hexane (I) were investigated separately in n-hexane and in methanol solutions over the temperature and concentration ranges of 393.2-443.2 K and 2.7-54 x l0-5 M, respectively. The values of the activation parameters for both reactions were compared with the corresponding ones for the thermolysis of cis-6-(4-fluorophenyl-5,6-[2-(4-fluorophenyl)-3-hydroxypropylidene]-3,3-tetramethylene-1,2,4-trioxacyclohexane (II), investigated in the same solvents and temperature range. Substituent and solvent effects on the initial homolytic rupture of the O-O peroxydic bonds of those molecules were evaluated.

UV spectroscopic analysis of a substituted 1,2,4-trioxane molecule: theoretical and experimental study of cis-6-phenyl-5,6-(2-phenyl propyliden)-3,3-tetramethylen-1,2,4-trioxacyclohexane

Abstract A theoretical and experimental study of cis -6-phenyl-5,6-(2-phenyl propyliden)-3,3-tetramethylen-1,2,4-trioxacyclohexane molecule was performed to look for their more stable conformations. This was accomplished considering the corresponding UV–VIS spectrum obtained in n -hexane solution and making the electronic band assignments on the basis of the molecular orbital picture.

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. Average absolute deviations from experimental results are rather low, which seems to point out the suitability of the present approach.

Theoretical Study of the trans-3,6-Dimethoxy-1,2,4-trioxane Molecule

The molecule of trans-3,6-dimethoxy-1,2,4-trioxane has been studied by the semiempirical molecular orbital AM1 and PM3 methods. The numerical results of the structural study have been analyzed in terms of several stereoelectronic effects and compared with available experimental data. Theoretical predictions derived from both methods are in a good agreement with each other.