Thermochemical Study of 1-Methylhydantoin

Using static bomb combustion calorimetry, the combustion energy of 1-methylhydantoin was obtained, from which the standard molar enthalpy of formation of the crystalline phase at T = 298.15 K of the compound studied was calculated. Through thermogravimetry, mass loss rates were measured as a function of temperature, from which the enthalpy of vaporization was calculated. Additionally, some properties of fusion were determined by differential scanning calorimetry, such as enthalpy and temperature. Adding the enthalpy of fusion to the enthalpy of vaporization, the enthalpy of sublimation of the compound was obtained at T = 298.15 K. By combining the enthalpy of formation of the compound in crystalline phase with its enthalpy of sublimation, the respective standard molar enthalpy of formation in the gas phase was calculated. On the other hand, the results obtained in the present work were compared with those of other derivatives of hydantoin, with which the effect of the change of some substituents in the base heterocyclic ring was evaluated.

A Promising Thermodynamic Study of Hole Transport Materials to Develop Solar Cells: 1,3-Bis(N-carbazolyl)benzene and 1,4-Bis(diphenylamino)benzene

The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir’s equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the 1H and 13C spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.

A Thermochemical Study of Iron Aluminate-Based Materials: A Preferred Class for Isothermal Water Splitting

The use of hydrogen as a renewable fuel has been stymied by our inability to produce it cleanly and economically. The conventional solar thermochemical approach considers a two-step redox cycle...

Synthesis, Molecular Structure, HOMO-LUMO, Chemical, Spectroscopic (UV-Vis and IR), Thermochemical Study of Ethyl 6-amino-5-cyano-2-methyl-4-(4-nitrophenyl)-4H-pyran-3-carboxylate: A DFT Exploration

The ethyl 6-amino-5-cyano-2-methyl-4-(4-nitrophenyl)-4H-pyran-3-carboxylate (ACNPPC) was synthesized using an environmentally friendly method and looked into in terms ofstructural, UV-visible, vibrational, and computational analysis. In the gaseous phase, calculations of the density functional theory (DFT) with B3LYP/6-311G(d,p) level were performed. Using Time-dependent density functional theory (TD-DFT) with the B3LYP/6-311G(d,p) basis set method, the HOMO and LUMO energies are calculated. For assessing electrophilic and nucleophilic reactive sites, the molecular electrostatic surface potential (MESP) and contour plot were plotted over the optimized structure. Using computed and experimental vibrational spectra, vibrational assignments were elucidated. To illustrate the charge density in the title compound, Mulliken atomic charges are disclosed. In addition, using vibrational analysis, some thermochemical functions have also been derived. Theoretical simulations have shown the best relationship with experimental results obtained with the B3LYP/6-311G(d,p) level of theory at the DFT and TD-DFT methods.

COMPARISON OF L-ASPARAGINE INTERACTIONS WITH PYRIDINE DERIVATIVES, PYRIDOXAL- 5'-PHOSPHATE AND PYRIDOXINE, IN AQUEOUS SOLUTIONS: THERMODYNAMIC ASPECTS

Interactions of proteins with various biologically active substances (hormones, drugs, enzymes, etc.) underlie many biochemical processes in the body. As part of the long-term task to studying various aspects of the interaction between model protein compounds and heterocyclic compounds that are into the structure of many enzymes and drugs, the thermochemical study of aqueous solutions containing aspartic acid amide (L-asparagine) and peridoxal-5¢-phosphate was carried out. Calorimetric measurements of the enthalpy of L-asparagine dissolution in an aqueous solution with pyridoxal-5¢-phosphate additives were performed on an ampoule-type isoperibolic dissolution calorimeter at 298.15 K. The error of measuring single heat effects was below 0.2%. The relative combined uncertainty in the measurements of the enthalpies of dissolution was not more than 0.7%. Based on the obtained experimental data and the using the HEAT computer program, the binding constants and thermodynamic parameters (lgK, ΔcG, ΔcH, ΔcS) of the complex formation between the reagents under study were calculated. A comparison of the affinity of amino acids to interaction with pyridoxal-5¢-phosphate and pyridoxine was carried out. The features of their behavior in an aqueous solution are revealed. It is shown that the interaction of L-asparagine with pyridoxine leads to the formation of a more stable complex than with peridoxal-5¢-phosphate. This fact may be explained in terms of a bulky phosphate group that hinders apparently the interaction of POP with aspartic acid amide. In addition, the peridoxal-5¢-phosphate molecule contains intramolecular hydrogen bonds between aldehyde CHO and phenolic OH groups, which must be destroyed by the interaction of peridoxal-5' - phosphate with an amino acid, which requires additional energy expenses. Thus, the selectivity of the interaction and the stability of the formed complexes are mainly regulated by the factors of structural and energy complementarity.