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© 2016 American Pharmacists Association®.Benzoic acid is a model compound for drug substances in pharmaceutical research. Process design requires information about thermodynamic phase behavior of benzoic acid and its mixtures with water and organic solvents. This work addresses phase equilibria that determine stability and solubility. In this work, Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to model the phase behavior of aqueous and organic solutions containing benzoic acid and chlorobenzoic acids. Absolute vapor pressures of benzoic acid and 2-, 3-, and 4-chlorobenzoic acid from literature and from our own measurements were used to determine pure-component PC-SAFT parameters. Two binary interaction parameters between water and/or benzoic acid were used to model vapor-liquid and liquid-liquid equilibria of water and/or benzoic acid between 280 and 413 K. The PC-SAFT parameters and 1 binary interaction parameter were used to model aqueous solubility of the chlorobenzoic acids. Additionally, solubility of benzoic acid in organic solvents was predicted without using binary parameters. All results showed that pure-component parameters for benzoic acid and for the chlorobenzoic acids allowed for satisfying modeling phase equilibria. The modeling approach established in this work is a further step to screen solubility and to predict the whole phase region of mixtures containing pharmaceuticals

Thermodynamic properties of 1,2-cyclohexanediols

© 2015 Pleiades Publishing, Ltd. The enthalpy values for the combustion and formation of crystalline cis and trans-1,2-cyclohexanediols are determined via bomb calorimetry. The vapor pressures of the compounds and their enthalpies of sublimation are measured. Using quantum-chemical methods, the reliability of the experimental data is estimated, the molecular structures of the compounds are studied, and the structures of the most stable conformers are established. The energy values of the intramolecular hydrogen bonds in the diol molecules are found

Vapor pressures and vaporization enthalpies of 5-nonanone, linalool and 6-methyl-5-hepten-2-one. Data evaluation

© 2014 Elsevier B.V.. Vapor pressures and vaporization enthalpies for 5-nonanone, linalool and 6-methyl-5-hepten-2-one seem to be in disarray. Temperature dependences of vapor pressures for these pure compounds were measured by using the static and the transpiration techniques. Molar standard enthalpies of vaporization at the reference temperature were derived. Available literature data on vapor pressures and vaporization enthalpies were collected and analyzed. The consistent data set for each compound was evaluated. Reliable thermodynamic parameters of vaporization were derived and used to test some commonly used predicting procedures

Thermochemistry of uracil and thymine revisited

© 2015 Published by Elsevier Ltd. Thermochemical properties of uracil and thymine have been evaluated using additional experiments. Standard (p0 = 0.1 MPa) molar enthalpies of formation in the gas phase at T = 298.15 K for uracil -(298.1 ± 0.6) and for thymine -(337.6 ± 0.9) kJ · mol-1 have been derived from energies of combustion measured by static bomb combustion calorimetry and molar enthalpies of sublimation determined using the transpiration method. The G3 and G4 quantum-chemical methods were used for calculations of theoretical gaseous enthalpies of formation being in very good agreement with the re-measured experimental values

Thermochemical Properties of Xanthine and Hypoxanthine Revisited

© 2017 American Chemical Society. The standard molar enthalpies of formation of xanthine and hypoxanthine were measured by using high-precision combustion calorimetry. The standard molar enthalpies of sublimation of these compounds at 298.15 K were derived by the quartz-crystal microbalance technique. Limited thermodynamic data available in the literature are compared with our new experimental data. In addition, we use the G4 method to calculate the molar enthalpies of formation of xanthine and hypoxanthine in the gas phase. There is good agreement between the evaluated experimental data and the quantum-chemical calculations. (Chemical Equation Presented)

Nearest-neighbor and non-nearest-neighbor interactions between substituents in the benzene ring. Experimental and theoretical study of functionally substituted benzamides

© 2016 American Chemical Society.Standard molar enthalpies of formation of 2- and 4-hydroxybenzamides were measured by combustion calorimetry. Vapor pressures of benzamide and 2-hydroxybenzamide were derived by the transpiration method. Standard molar enthalpies of sublimation or vaporization of these compounds at 298 K were obtained from vapor pressure temperature dependence. Thermochemical data on benzamides with hydroxyl, methyl, methoxy, amino, and amide substituents were collected, evaluated, and tested for internal consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. Sets of nearest-neighbor and non-nearest-neighbor interactions between substituents in the benzene ring have been evaluated. A simple incremental procedure has been suggested for a quick appraisal of the vaporization and gas-phase formation enthalpies of the substituted benzamides. (Chemical Equation Presented)

Structure–property relationships in halogenbenzoic acids: Thermodynamics of sublimation, fusion, vaporization and solubility

© 2016 Elsevier LtdTemperature dependences of vapor pressures for 2-, 3-, and 4-bromobenzoic acid, as well as for five isomeric bromo-methylbenzoic acids were studied by the transpiration method. Melting temperatures and enthalpies of fusion for all isomeric bromo-methylbenzoic acids and 4-bromobenzoic acid were measured with a DSC. The molar enthalpies of sublimation and vaporization were derived. These data together with results available in the literature were collected and checked for internal consistency using a group-additivity procedure and results from X-ray structural diffraction studies. Specific (hydrogen bonding) interactions in the liquid and in the crystal phase of halogenbenzoic acids were quantified based on experimental values of vaporization and sublimation enthalpies. Structure-property correlations of solubilities of halogenobenzoic acids with sublimation pressures and sublimation enthalpies were developed and solubilities of bromo-benzoic acids were estimated. These new results resolve much of the ambiguity in the available thermochemical and solubility data on bromobenzoic acids. The approach based on structure property correlations can be applied for the assessment of water solubility of sparingly soluble drugs

Individual variation in seasonal movements and foraging strategies of a land-locked, ice-breeding pinniped

Marine mammal satellite telemetry studies can provide important tests of movement and foraging theory. Here we present the first satellite tracking study of Caspian seals (Pusa caspica), an endangered, ice-breeding phocid seal, endemic to the Caspian Sea. The Caspian Sea is one of the most variable habitats inhabited by any pinniped species, and lacks competing large piscivores. Under such conditions foraging theory predicts individual variation in foraging strategy may develop to reduce intra-species competition. We deployed 75 Argos satellite tags 2009-2012 on adult seals of both sexes, and used State Space Modelling to describe movement, and behavioural states. During winter in all years most individuals were mobile within the icepack, making repeated trips into open water outside the ice field, with only brief stationary periods that may be related to breeding activity. During summer 2011, 60% of tagged animals migrated into the mid and southern Caspian, while the remainder spent the ice free season in the north. Summer foraging locations were not restricted by proximity to haul out sites, with animals spending more than 6 months at sea. Maximum dive depths exceeded 200m, and maximum duration was greater than 20 minutes, but 80% of dives were shallower than 15m and shorter than 5 minutes. Hierarchical cluster analysis identified 3 distinct groups of summer dive behaviour, comprising shallow, intermediate and deep divers, which were also spatially exclusive, suggesting potential niche partitioning and individual specialisation on prey or habitat types. The results can contribute to assessment of impacts from anthropogenic activities and to designation of protected areas encompassing critical habitats

Thermochemical properties of different 1-(R-phenyl)-1H-imidazoles

© 2016 Elsevier B.V.Phenyl substituted imidazoles exhibit versatile biological activity. 1-(R-phenyl)-1H-imidazoles with different functional groups R provide a convenient suitcase of molecules with tunable physicochemical properties adjustable for many practical applications. In this work, the absolute vapor pressures of 1-(R-phenyl)-1H-imidazoles (with R = H, 2-methyl, 4-methyl, 2-methoxy, 4-methoxy, 2-fluoro, 4-fluoro, 2-bromo and 4-bromo) at different temperatures have been measured by the transpiration method for the first time. The standard enthalpies of vaporization of these compounds were derived from the temperature dependencies of the vapor pressures. An internal consistency of the standard vaporization enthalpies has been proven by comparison with vaporization enthalpies of parent species, as well as by a group contribution method. A system of group-additivity values is suggested for a quick assessment of vaporization enthalpies of different 1-(R-phenyl)-1H-imidazoles. Gas-phase standard molar enthalpies of formation of 1-(R-phenyl)-1H-imidazoles have been calculated using the high-level quantum-chemical method G3MP2. The combination of experimentally determined standard vaporization enthalpies with the G3MP2 results allows for the prediction of the liquid-phase standard enthalpies of formation for the studied compounds