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.

Thermodynamics Properties of 1,1-Carbonyldiimidazole (CDI) and 4-Imidazole Acrylic Acid, Obtained by DSC and Combustion Calorimetry

In this work, thermodynamic properties of 1,1-carbonyldiimidazole (CDI) and 4-imidazole acrylic are reported. The melting temperature, the enthalpy of fusion and the heat capacity of the compounds were determined by differential scanning calorimetry. The standard molar energy of combustion of both compounds were determined by static-bomb combustion calorimetry and the standard molar enthalpy of formation in the crystalline phase, at T = 298.15 K, was derived and evaluated for the two imidazole derivatives studied. The energetic influence of the acrylic group on the imidazole ring in each of the properties obtained is analyzed and compared with the existing results in the literature. Resumen. Se presentan las propiedades termodinámicas del 1,1-carbonildiimidazol (CDI) y el 4-imidazol acrílico. La temperatura de fusión, la entalpía de fusión y la capacidad calorífica de los compuestos se determinaron mediante calorimetría diferencial de barrido. La energía molar estándar de la combustión de ambos compuestos se determinó mediante calorimetría de combustión en bomba estática y la entalpía de formación en fase cristalina, a T= 298.15, fue derivada y evaluada para los dos compuestos derivados del imidazol. La influencia energética del grupo acrílico sobre el anillo de imidazol en cada una de las propiedades obtenidas se analiza y compara con los resultados existentes en la literatura.

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.