Enthalpies of fusion and enthalpies of solvation of aromatic hydrocarbons derivatives: Estimation of sublimation enthalpies at 298.15 K

© 2016 Elsevier B.V. All rights reserved.Enthalpy of sublimation of solid compound can be found using the values of solution enthalpy and solvation enthalpy in any solvent. In this work enthalpies of solution at infinite dilution of a number of aromatic hydrocarbons derivatives in benzene were measured at 298.15 K. Comparison between experimental and literature solution enthalpies in benzene at 298.15 K and fusion enthalpies at melting temperature of aromatic hydrocarbon derivatives showed, that these values are approximately equal. Thereby, fusion enthalpies at melting temperature can be used instead of their solution enthalpies in benzene at 298.15 K for calculation of sublimation enthalpies at 298.15 K. Solvation enthalpies in benzene at 298.15 K required for this procedure were calculated using group additivity scheme. The sublimation enthalpies of 80 aromatic hydrocarbons derivatives at 298.15 K were evaluated as a difference between fusion enthalpies at melting temperature and solvation enthalpies in benzene at 298.15 K. Obtained in this work values of sublimation enthalpy at 298.15 K for studied compounds were in a good agreement with available literature data

Thermochemical properties of mono- and di-cyano-aromatic compounds at 298.15 K

© 2018 Elsevier B.V. The solution calorimetry approach was applied for the determination of the sublimation enthalpies for cyano-aromatic compounds. According to this approach, the vaporization/sublimation enthalpies were estimated as a difference between solution (cr/l to the solution) and solvation (gas to the solution) enthalpies in acetonitrile as a solvent. The solvation enthalpy of studied compounds was calculated using the previously developed and tested additive scheme. The solution enthalpies of five cyano-aromatic compounds were measured experimentally for the first time by using solution calorimeter. The new approach for the evaluation of the condensed state enthalpy of formation by using first principles calculations and solution calorimetry technique is proposed. In most cases obtained results are in good agreement with literature values. Apparatus for determination of vapor pressure by using the transpiration method was developed. The experimental setup was tested by measuring the vapor pressure of pure naphthalene. Vapor pressures for 1- and 2-cyano-naphthalenes were measured by using the newly elaborated transpiration setup. Experimental and calculated values of sublimation enthalpies are in good agreements with the most reliable available literature data. Sublimation enthalpy of 9-cyano-anthracene was obtained by solution calorimetry for the first time

New method for determination of vaporization and sublimation enthalpy of aromatic compounds at 298.15 K using solution calorimetry technique and group-additivity scheme

© 2015 Elsevier B.V. All rights reserved. In this work a new method for determination of vaporization/sublimation enthalpies of aromatic compounds directly at T = 298.15 K was developed. This method is based on the general relationship between vaporization/sublimation enthalpy and enthalpies of solution and solvation of the studied compound in any solvent. According to this method the procedure for determination of vaporization (liquids) or sublimation (solids) enthalpy includes measurement of the solution enthalpy of the compound in a selected solvent and calculation of the solvation enthalpy for this system. A group-additivity scheme for calculation of solvation enthalpies is proposed. The solvation enthalpy of compound is estimated from the solvation enthalpy of parent aromatic or heteroaromatic compound and contributions of the substituent groups. Limiting solution enthalpies of 34 aromatic compounds (substituted benzenes, naphthalenes, biphenyls, pyrene, anthracene and pyridines) in carbon tetrachloride, benzene, acetonitrile and N,N-dimethylformamide were measured in the present work at 298.15 K. Vaporization/sublimation enthalpies of 78 aromatic and heteroaromatic compounds were determined directly at 298.15 K using experimentally measured solution enthalpies and predicted values of solvation enthalpies. The results are in good agreement with available literature data

Enthalpies of fusion and enthalpies of solvation of aromatic hydrocarbons derivatives: Estimation of sublimation enthalpies at 298.15 K

© 2016 Elsevier B.V. All rights reserved.Enthalpy of sublimation of solid compound can be found using the values of solution enthalpy and solvation enthalpy in any solvent. In this work enthalpies of solution at infinite dilution of a number of aromatic hydrocarbons derivatives in benzene were measured at 298.15 K. Comparison between experimental and literature solution enthalpies in benzene at 298.15 K and fusion enthalpies at melting temperature of aromatic hydrocarbon derivatives showed, that these values are approximately equal. Thereby, fusion enthalpies at melting temperature can be used instead of their solution enthalpies in benzene at 298.15 K for calculation of sublimation enthalpies at 298.15 K. Solvation enthalpies in benzene at 298.15 K required for this procedure were calculated using group additivity scheme. The sublimation enthalpies of 80 aromatic hydrocarbons derivatives at 298.15 K were evaluated as a difference between fusion enthalpies at melting temperature and solvation enthalpies in benzene at 298.15 K. Obtained in this work values of sublimation enthalpy at 298.15 K for studied compounds were in a good agreement with available literature data

Hexamorphism of Dantrolene: Insight into the Crystal Structures, Stability, and Phase Transformations

Dantrolene represents yet another interesting example of abundant molecular crystal polymorphism existing in at least six different neat polymorphs, three of which can be obtained via crystallization (I-III) and an additional three (IV- VI) via solid-state dehydration from three different monohydrates (MH-I-MH-III). The reasons for polymorph formation were rationalized by analyzing the crystal structures of the polymorphs and hydrates used in their preparation. The thermodynamic relations among the polymorphs were established from calorimetric data, solubility measurements, and lattice energy calculations

Fast scanning calorimetry: Sublimation thermodynamics of low volatile and thermally unstable compounds

© 2019 Elsevier B.V. Fast scanning calorimetry (FSC) was applied for measurements of the sublimation rates of theophylline, caffeine and anthraquinone as reference compounds. In comparison to conventional vapor pressure determination techniques, this method requires only nano-gram-size samples. The increased surface to volume ratio allows for very high sublimation rates and makes the sublimation process dominant over a possible decomposition. Experimental conditions and data treatment have been elaborated and validated by comparison with reliable literature data. The FSC method “opens a new door” for reliable experimental determination of vapor pressures and sublimation enthalpies for very low volatile and thermally unstable compounds like bio-relevant molecules

Fast scanning calorimetry: Sublimation thermodynamics of low volatile and thermally unstable compounds

© 2019 Elsevier B.V. Fast scanning calorimetry (FSC) was applied for measurements of the sublimation rates of theophylline, caffeine and anthraquinone as reference compounds. In comparison to conventional vapor pressure determination techniques, this method requires only nano-gram-size samples. The increased surface to volume ratio allows for very high sublimation rates and makes the sublimation process dominant over a possible decomposition. Experimental conditions and data treatment have been elaborated and validated by comparison with reliable literature data. The FSC method “opens a new door” for reliable experimental determination of vapor pressures and sublimation enthalpies for very low volatile and thermally unstable compounds like bio-relevant molecules

Enthalpies of fusion and enthalpies of solvation of aromatic hydrocarbons derivatives: Estimation of sublimation enthalpies at 298.15 K

© 2016 Elsevier B.V. All rights reserved.Enthalpy of sublimation of solid compound can be found using the values of solution enthalpy and solvation enthalpy in any solvent. In this work enthalpies of solution at infinite dilution of a number of aromatic hydrocarbons derivatives in benzene were measured at 298.15 K. Comparison between experimental and literature solution enthalpies in benzene at 298.15 K and fusion enthalpies at melting temperature of aromatic hydrocarbon derivatives showed, that these values are approximately equal. Thereby, fusion enthalpies at melting temperature can be used instead of their solution enthalpies in benzene at 298.15 K for calculation of sublimation enthalpies at 298.15 K. Solvation enthalpies in benzene at 298.15 K required for this procedure were calculated using group additivity scheme. The sublimation enthalpies of 80 aromatic hydrocarbons derivatives at 298.15 K were evaluated as a difference between fusion enthalpies at melting temperature and solvation enthalpies in benzene at 298.15 K. Obtained in this work values of sublimation enthalpy at 298.15 K for studied compounds were in a good agreement with available literature data

Sublimation thermodynamics of nucleobases derived from fast scanning calorimetry

© 2020 the Owner Societies. The five fundamental units of the genetic code: Uracil (U), thymine (T), cytosine (C), adenine (A) and guanine (G) are known for extremely low vapor pressure and low thermal stability at elevated temperatures. Therefore, application of conventional techniques for the determination of sublimation enthalpies and vapor pressures fails to provide accurate results. Recently, a Fast Scanning Calorimetry method (FSC) for vapor pressure determination was developed for investigation of extremely low volatile, as well as for thermally unstable molecular and ionic molecules. This success has encouraged application of the FSC method for determination of vapor pressures and sublimation enthalpies of the five nucleobases, where available literature data are in disarray. The thermodynamic data of the nucleobases available in the literature were collected, evaluated, and combined with our experimental results to reconcile available experimental data. The set of evaluated thermochemical data on the five nucleobases was recommended as the benchmark properties for these thermally labile compounds

Enthalpies of fusion and enthalpies of solvation of aromatic hydrocarbons derivatives: Estimation of sublimation enthalpies at 298.15 K

© 2016 Elsevier B.V. All rights reserved.Enthalpy of sublimation of solid compound can be found using the values of solution enthalpy and solvation enthalpy in any solvent. In this work enthalpies of solution at infinite dilution of a number of aromatic hydrocarbons derivatives in benzene were measured at 298.15 K. Comparison between experimental and literature solution enthalpies in benzene at 298.15 K and fusion enthalpies at melting temperature of aromatic hydrocarbon derivatives showed, that these values are approximately equal. Thereby, fusion enthalpies at melting temperature can be used instead of their solution enthalpies in benzene at 298.15 K for calculation of sublimation enthalpies at 298.15 K. Solvation enthalpies in benzene at 298.15 K required for this procedure were calculated using group additivity scheme. The sublimation enthalpies of 80 aromatic hydrocarbons derivatives at 298.15 K were evaluated as a difference between fusion enthalpies at melting temperature and solvation enthalpies in benzene at 298.15 K. Obtained in this work values of sublimation enthalpy at 298.15 K for studied compounds were in a good agreement with available literature data