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Abstract  

The standard (p 0=0.1 MPa) molar enthalpy of formation, Δf H m 0(l)=169.8±2.6 kJ mol−1, of the liquid 3-bromoquinoline was derived from its standard molar energy of combustion, in oxygen, to yield CO2(g), N2(g) and HBr·600H2O(l), at T=298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpy of vaporization of the compound, Δ1 g H m 0=70.7±2.3 kJ mol−1. These two thermodynamic parameters yielded the standard molar enthalpy of formation, in the gaseous phase, at T=298.15 K, Δf H m 0(g)=240.5±3.5 kJ mol−1.

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Abstract  

The standard (p 0=0.1 MPa) molar enthalpy of formation of 1-cyanoacetylpiperidine, in the crystalline state, at T=298.15 K, has been derived from measurements of its standard massic energy of combustion, by static bomb combustion calorimetry, as Δf H m 0=−217.1±1.4 kJ mol−1. The standard molar enthalpy of sublimation was measured, at T=298.15 K, by the microcalorimetric sublimation technique as Δcr g H m 0=103.5±1.9 kJ mol−1.

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Abstract  

The standard (p 0=0.1 MPa) molar enthalpy of formation, Δf H 0 m, for crystalline N-phenylphthalimide was derived from its standard molar enthalpy of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry, as –206.03.4 kJ mol–1. The standard molar enthalpy of sublimation, Δg cr H 0 m , at T=298.15 K, was derived, from high temperature Calvet microcalorimetry, as 121.31.0 kJ mol–1. The derived standard molar enthalpy of formation, in the gaseous state, is analysed in terms of enthalpic increments and interpreted in terms of molecular structure.

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Abstract  

The standard (p 0=0.1 MPa) molar enthalpies of formation, in the condensed phase, of nine linear-alkyl substituted thiophenes, six in position 2- and three in position 3-, at T=298.15 K, were derived from the standard massic energies of combustion, in oxygen, to yield CO2(g) and H2SO4·115H2O(aq), measured by rotating-bomb combustion calorimetry. The standard molar enthalpies of vaporization of these compounds were measured by high temperature Calvet Microcalorimetry, so their standard molar enthalpies of formation, in the gaseous phase, were derived. The results are discussed in terms of structural contributions to the energetics of the alkyl-substituted thiophenes, and empirical correlations are suggested for the estimation of the standard molar enthalpies of formation, at T=298.15 K, for 2- and 3-alkyl-substituted thiophenes, both in the condensed and in the gaseous phases.

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Abstract  

The present work is part of a broader research program on the energetics of formation of heterocycles, aiming the study of the enthalpic effects of the introduction of different substituents into heterocycles. In this work we present the results of the thermochemical research on sulphur heterocycles of the type substituted thiophenes with different kind of substituents, mainly alkyl, ester, acetyl, carboxamide, acetamide, carbonitrile and carboxaldehyde. The standard (p o=0.1 MPa) molar enthalpies of formation, in the condensed phase, at T=298.15 K, of a large number of substituted thiophenes, were derived from their standard massic energies of combustion, measured by rotating-bomb combustion calorimetry, while the standard molar enthalpies of vaporization or sublimation of those compounds were obtained either by high temperature Calvet Microcalorimetry, or by the temperature dependence of their vapour pressures determined by the Knudsen effusion technique. The standard molar enthalpies of formation, of the studied sulphur heterocycles in the gaseous phase, were then derived. The results are interpreted in terms of structural contributions to the energetics of the substituted thiophenes, the internal consistency of the results is discussed and, whenever appropriate and possible, empirical correlations are suggested for the estimation of standard molar enthalpies of formation, at T=298.15 K, of substituted thiophenes. A Table of enthalpic increments for different group substituents in positions 2 or 3 of the thiophene ring has been established.

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Thermochemical properties of three piperidine derivatives

1-benzyl-4-piperidinol, 4-benzylpiperidine and 4-piperidine-piperidine

Journal of Thermal Analysis and Calorimetry
Authors: M. Ribeiro da Silva and Joana Cabral

Abstract  

The standard (p o=0.1 MPa) molar energies of combustion for the crystalline 1-benzyl-4-piperidinol and 4-piperidine-piperidine, and for the liquid 4-benzylpiperidine, were measured by static bomb calorimetry, in oxygen, at T=298.15 K. The standard molar enthalpies of sublimation or vaporization, at T=298.15 K, of these three compounds were determined by Calvet microcalorimetry. Those values were used to derive the standard molar enthalpies of formation, at T=298.15 K, in their condensed and gaseous phase, respectively.

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Journal of Thermal Analysis and Calorimetry
Authors: Maria Ribeiro da Silva, N. Araújo, A. Silva, L. da Silva, N. Barros, J. Gonçalves, and M. Ribeiro da Silva

Abstract  

The standard (p 0=0.1 MPa) molar enthalpies of formation, at T=298.15 K, in the gaseous phase, for three tetradentate Schiff bases involving a N2O2 set, N,N’-bis(salicylaldehydo)cyclohexanediimine (H2salch), N,N’-bis(acetylacetone)cyclohexanediimine (H2acacch) and N,N’-bis(benzoylacetone)cyclohexanediimine (H2bzacch), were determined from their enthalpies of combustion and sublimation, obtained by static bomb calorimetry in oxygen and by the Knudsen effusion technique, respectively. The results are compared with identical parameters for related compounds previously studied, resulting from the condensation of salicylaldehyde or β-diketone with aliphatic diamines.

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Abstract  

The standard (p 0=0.1 MPa) molar enthalpies of formation, Δf H m 0, for crystalline phthalimides: phthalimide, N-ethylphthalimide and N-propylphthalimide were derived from the standard molar enthalpies of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry, as, respectively, – (318.01.7), – (350.12.7) and – (377.32.2) kJ mol–1. The standard molar enthalpies of sublimation, Δcr g H m 0, at T=298.15 K were derived by the Clausius-Clapeyron equation, from the temperature dependence of the vapour pressures for phthalimide, as (106.91.2) kJ mol–1 and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide as, respectively, (106.31.3), (91.01.2) and (98.21.4) kJ mol–1. The derived standard molar enthalpies of formation, in the gaseous state, are analysed in terms of enthalpic increments and interpreted in terms of molecular structure.

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Journal of Thermal Analysis and Calorimetry
Authors: G. Mrevlishvili, A. Carvalho, M. Ribeiro da Silva, T. Mdzinarashvili, G. Razmadze, and T. Tarielashvili
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Journal of Thermal Analysis and Calorimetry
Authors: G. Mrevlishvili, M. Sottomayor, M. Ribeiro da Silva, T. Mdzinarashvili, M. Al-Zaza, M. Tediashvili, D. Tushishvili, and N. Chanishvili

Abstract  

Bacterial viruses genome- ds-DNA -expulsion from the phage capsid is induced by temperature and is not accompanied by heat effects (temperature interval 45–75°C). Thus the temperature induced ejection of genetic material from phages is predominantly entropic. ds-DNA output from the capsid increases the viscosity of the phage suspension at least 100 times. ds-DNA output from the capsid is accompanied by a significant change of partial volume. The disruption of 1mg of phage produces ΔV=1.3×10–9 m3 which corresponds to a volume increase of 200%. This produces exothermic heat effects in closed calorimetric cells, with free volume above the measured liquid. This paper deals with the study of the V-group, family T-even, E. Coli bacteria phage (named unphage). According to electron microscopic pictures, the geometrical parameters of this phage are 750×560 Å (from head) and 900 Å (from tail).

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