Experimental and Theoretical Investigation on the Thermochemistry of 3-Methyl-2-benzoxazolinone and 6-Nitro-2-benzoxazolinone

The determination of the reliable thermodynamic properties of 2-benzoxazolinone derivatives is the main goal of this work. Some correlations are established between the energetic properties determined and the structural characteristics of the title compounds, and the reactivity of this class of compounds is also evaluated. Static-bomb combustion calorimetry and high-temperature Calvet microcalorimetry were used to determine, respectively, the standard molar enthalpies of formation in the solid state and the standard molar enthalpies of sublimation, both at T = 298.15 K. Using the results obtained for each compound, the respective gas-phase standard molar enthalpy of formation was derived. High-level quantum chemical calculations were performed to estimate the same property and the results evidence good accordance. Moreover, the gas-phase relative thermodynamic stability of 2-benzoxazolinone derivatives was also evaluated using the respective gas-phase standard molar Gibbs energy of formation. In addition, the relationship between the energetic and structural characteristics of the benzoxazolinones is presented, evidencing the enthalpic increments associated with the presence of a methyl and a nitro groups in the molecule, and this effect is compared with similar ones in other structurally related compounds.

Energetic and Structural Studies of Two Biomass-Derived Compounds: 6- and 7-hydroxy-1-indanones

The energetic study of 6-hydroxy-1-indanone and 7-hydroxy-1-indanone was performed using experimental techniques and computational calculations. The enthalpies of combustion and sublimation of the two compounds were determined and allowed to derive the corresponding gas-phase standard molar enthalpies of formation. For this purpose, static-bomb combustion calorimetry and drop-method Calvet microcalorimetry were the experimental techniques used. Further, the enthalpy of fusion of each compound was obtained from scanning differential calorimetry measurements. Additionally, the gas-phase standard molar enthalpies of formation of these compounds were calculated through high-level ab initio calculations. The computational study of the molecular structures of the indanones was carried out and two possible conformers were observed for 6-hydroxy-1-indanone. Furthermore, the energetic effects associated with the presence of one hydroxyl group as a substituent on the benzenic ring of 1-indanone were also evaluated. Both experimental and theoretical methods show that 7-hydroxy-1-indanone is thermodynamically more stable than the 6-isomer in the gaseous phase and these results provide evidence for the existence of a strong intramolecular H-bond in 7-hydroxy-1-indanone. Finally, the intramolecular proton transfer in 7-hydroxy-1-indanone has been evaluated and as expected, it is not energetically favorable.

Influence of the functional groups −NH2, −OCH3, and −OH on the thermochemistry of indanes

This work is a contribution to the thermochemical characterization of bicyclic hydrocarbons, reporting the study of six indane derivatives: 4-aminoindane, 5-aminoindane, 5-methoxyindane, 1-indanol, 2-indanol, and 5-indanol. The combustion calorimetry technique was used to measure the massic energy of combustion of each compound in the condensed state, which has been used to derive the corresponding standard (p° = 0.1 MPa) molar enthalpy of formation, at 298.15 K. The standard molar enthalpies of sublimation or vaporization of the compounds were determined by high-temperature Calvet microcalorimetry. For each indane derivative, the results obtained for those two properties, allowed to derive the respective value of standard molar enthalpy of formation, in the gaseous phase. Additionally, a theoretical study at the G3(MP2)//B3LYP level has been carried out, and the calculated enthalpies of formation have been compared with the experimental values. The values of the enthalpy of formation, in the gaseous phase, were analysed in terms of correlations between the structural (different substituents in the indane core) and energetics characteristics.

Electomagnetic absorption of composites based on epoxy resin and metallic iron nanoparticles

The heat losses originated from the electro-magnetic absorption in magnetic epoxy-based composites with embedded metallic iron nanoparicles were studied by Calvet microcalorimetry. Iron magnetic nanoparticles (MNPs) were synthesized by electrical explosion of wire (EEW) method; they were non-agglomerated, spherical in shape and had a weight average diameter 85 nm. Composites based on the cured epoxy-dian resin contained MNPs in weight content varying from 10% up to 70% . To study the heat loss in alterating magnetic field commercial Calvet microcalorimeter was equiped by two coils in the serial connection placed in the calorimeter cells; one of the coils contained a sample of composite the other was a reference. The electromagnetic adsorption was studied in the alternating magnetic field up to 1700 A /m in 67 – 214 kHz frequency range. The measured values of the specific power losses revealed linear dependence on iron MNPs content in composite and non-linear increasing function of the field frequency.