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.

Oxidation of o-Dioxime by (Diacetoxyiodo)benzene: A Green and Mild Access to Furoxans

Furoxan has been widely used in the field of high energy density materials because of its excellent properties such as high ener-gy density, high standard enthalpy of formation and high...

THERMODYNAMIC FUNCTIONS OF FORMATION OF LITHIUM TITANATES

By the method of electromotive forces measuring concentration chains: Pt│Li2O│ ZrO2+10 wt% Y2O3, lithium glass. (Li2O)x(TiO2)1-x│Pt in the temperature range T=1000–1200K and concentrations 0.35÷0.95 mol fraction TiO2, the thermodynamic functions of the formation of the compounds Li4TiO4, Li2TiO3, Li4Ti5O12 and phases based on Li2TiO3:Li1.92Ti1.04O3.04, Li2.12Ti0.94O2.92 were determined. With the exception of the compound Li2TiO3, the thermodynamic functions of the formation of lithium titanates are deter¬mined for the first time. The thermodynamic functions of formation are calculated for the 1200 K and for the standard state at 298 K. The thermodynamic functions of the formation of lithium titanates are determined from simple substances and from binary compounds Li2O and TiO2. In particular, for the free energy, enthalpy of formation and standard entropy we obtained: ∆G_298^0(Li4TiO4)=–2149 kJ∙mol-1; ∆G_298^0(Li2TiO3)=–1565; ∆G_298^0(Li4Ti5O12)=–5923; ∆H_298^0(Li4TiO4)=–2286 kJ∙mol-1; ∆H_298^0(Li2TiO3)=–1662; ∆H_298^0(Li4Ti5O12)=–6287; S_298^0(Li4TiO4)=119.1 J∙mol-1∙K-1; S_298^0(Li2TiO3)=84; S_298^0(Li4Ti5O12)=315.7

Thermodynamic functions of ibuprofen

A conformational analysis has been conducted, structures that make a significant contribution to properties are selected, and the partial thermodynamic functions of ibuprofen conformers are calculated. The temperature dependences of molar fractions and entropy of mixing are obtained. Quantum-chemical and empirical estimates of the standard enthalpy of formation are produced. The thermodynamic functions of ibuprofen in the gas phase are determined.

GRAPHIC DEPENDENCES IN THE STUDY OF STRUCTURE - PROPERTIES OF GLYCOLS

Обсуждается взаимосвязь энтальпии образования двухатомных спиртов с различными факторами химического строения. Построены и проанализированы графические зависимости «Энтальпия образования - топологический индекс (ТИ)», «Энтальпия образования - номер изомера» и «Топологический индекс - номер изомера». Показано, что в одних случаях энтальпия образования хорошо коррелирует с ТИ, а в других случаях такой зависимости нет. The relationship between the enthalpy of formation of dihydric alcohols and various factors of chemical structure is discussed. Graphical dependencies "Enthalpy of formation - topological index (TI)", "Enthalpy of formation - isomer number" and "Topological index - isomer number" were constructed and analyzed. It was shown that in some cases the enthalpy of formation correlates well with TI, while in other cases there is no such dependence.

Sharp Bounds of First Zagreb Coindex for F -Sum Graphs

Let G = V E , E G be a connected graph with vertex set V G and edge set E G . For a graph G, the graphs S(G), R(G), Q(G), and T(G) are obtained by applying the four subdivisions related operations S, R, Q, and T, respectively. Further, for two connected graphs G 1 and G 2 , G 1 + F G 2 are F -sum graphs which are constructed with the help of Cartesian product of F G 1 and G 2 , where F ∈ S , R , Q , T . In this paper, we compute the lower and upper bounds for the first Zagreb coindex of these F -sum (S-sum, R-sum, Q-sum, and T-sum) graphs in the form of the first Zagreb indices and coincides of their basic graphs. At the end, we use linear regression modeling to find the best correlation among the obtained results for the thirteen physicochemical properties of the molecular structures such as boiling point, density, heat capacity at constant pressure, entropy, heat capacity at constant time, enthalpy of vaporization, acentric factor, standard enthalpy of vaporization, enthalpy of formation, octanol-water partition coefficient, standard enthalpy of formation, total surface area, and molar volume.