No abstract

Indole and methylindole are heterocyclic aromatics, which can be hydrogenated and used for hydrogen storage. A huge advantage of heterocyclic components compared to homocyclic aromatics is the lower enthalpy of reaction for hydrogen release by dehydrogenation. In this study, thermochemical properties of indole and 2-methylindole and its partially and fully hydrogenated derivatives have been determined. Hydrogenation of indoles is a two-step reaction, which is highly influenced by reaction thermodynamics. High precision combustion calorimetry was used to measure enthalpies of formation of indole derivatives. The gas-phase enthalpies of formation were derived with the help of vapor pressure measurements. The high-level quantum-chemical methods were used to establish consistency of the experimental data. The standard molar thermodynamic functions of formation (enthalpy, entropy, and Gibbs energy) of indole derivatives were derived. The results showed that the partially hydrogenated species, 2-methylindoline, tends to dehydrogenate easily under hydrogen release conditions. Thus, indoline is only expected in trace amounts in the respective reaction mixture.

Cellulose-derived platform chemicals offer viable substitutes for most petroleumbased polymers and also enable the development of novel functional materials. In the focus of this work are thermophysical and thermochemical studies of dihydro-levoglucosenone (Cyrene) and levoglucosenone, which are considered as potential "green" replacements for industrial polar aprotic solvents. The densities, viscosities, absolute vapor pressures, and combustion energies of cyrene and levoglucosenone were measured in this work. The thermodynamic properties of levoglucosan derivatives are reliable for thermochemical calculations and used to calculate reaction enthalpies of valorization of the cellulose component of biomass. These enthalpies of reaction are useful in the further optimization and development of sustainable syntheses of commodity chemicals and fuels from biomass. The data provided in this work will aid researchers and engineers as the use of these new solvents grows.

The purpose of this study was to characterize essential changes in the structure of annulus fibrosus (AF) after hydrothermal and infrared (IR) laser treatment and to correlate these results with alterations in tissue state. Polarization-sensitive optical coherence tomography imaging was used to measure collagen birefringence in AF. Differential scanning calorimetry was used as a complementary technique, providing detailed information on thermodynamic processes in the tissue. Birefringence, peak of the denaturation endotherm, and the enthalpy of denaturation (DeltaHm) were determined before and after hydrothermal heat treatment (85 degrees C for 15 min) and non-ablative Er:glass fiber laser exposures on AF in the whole disk (vertebrae-disk-vertebrae complex). Our data have demonstrated quantitative differences between results of laser and hydrothermal heating. Birefringence did not disappear and DeltaHm did not change after treatment in the water bath, but loss of birefringence and a decrease in the enthalpy did occur after laser exposure. These results could be explained by the photomechanical effect of laser irradiation. We suggest that thermo-mechanical stress played a dominant role in the disruption of the collagen network of AF under non-homogeneous laser heating.