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The need to transition from fossil fuels to renewables arises from factors such as depletion, price fluctuations, and environmental considerations. Lignocellulosic biomass, being abundant, and quickly renewable, and not interfering with food supplies, offers a standout alternative for chemical production. This paper explores the energetic characteristics of two derivatives of furfural—a versatile chemical obtained from biomass with great potential for commercial sustainable chemical and fuel production. The standard (p° = 0.1 MPa) molar enthalpies of formation of the liquids furfurylamine and 5-methylfurfurylamine were derived from the standard molar energies of combustion, determined in oxygen and at T = 298.15 K, by static bomb combustion calorimetry. Their standard molar enthalpies of vaporization were also determined at the same temperature using high-temperature Calvet microcalorimetry. By combining these data, the gas-phase enthalpies of formation at T = 298.15 K were calculated as −(43.5 ± 1.4) kJ·mol−1 for furfurylamine, and −(81.2 ± 1.7) kJ·mol−1 for 5-methylfurfurylamine. Furthermore, a theoretical analysis using G3 level calculations was performed, comparing the calculated enthalpies of formation with the experimental values to validate both results. This method has been successfully applied to similar molecules. The discussion looks into substituent effects in terms of stability and compares them with similar compounds.

This paper reports an experimental and theoretical study of the gas phase standard (p° = 0.1 MPa) molar enthalpies of formation, at T= 298.15 K, of α-alanine (DL) and β-alanine. The standard (p° = 0.1 MPa) molar enthalpies of formation of crystalline α-alanine (DL) and β-alanine were calculated from the standard molar energies of combustion, in oxygen, to yield CO2(g), N2(g), and H2O(l), measured by static-bomb combustion calorimetry at T= 298.15 K. The vapor pressures of both amino acids were measured as function of temperature by the Knudsen effusion mass-loss technique. The standard molar enthalpies of sublimation at T= 298.15 K was derived from the Clausius−Clapeyron equation. The experimental values were used to calculate the standard (p° = 0.1 MPa) enthalpy of formation of α-alanine (DL) and β-alanine in the gaseous phase, ΔfHm°(g), as −426.3 ± 2.9 and −421.2 ± 1.9 kJ·mol−1, respectively. Standard ab initio molecular orbital calculations at the G3 level were performed. Enthalpies of formation, using atomization reactions, were calculated and compared with experimental data. Detailed inspections of the molecular and electronic structures of the compounds studied were carried out. [ABSTRACT FROM AUTHOR]

Thermochemical and thermodynamic properties of 2,5-dimethyl-1-phenylpyrrole and 2,5-dimethyl-1-(4-nitrophenyl)pyrrole have been determined by using a combination of calorimetric and effusion techniques as well as high-level ab initio molecular orbital calculations. The standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline state, ΔfHm°(cr), at T= 298.15 K, were derived from the standard molar enthalpies of combustion, ΔcHm°, which were obtained from static bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to determine the standard molar enthalpies of sublimation, ΔcrgHm°, at T= 298.15 K. From the experimental results, the standard molar enthalpies of formation, in the gaseous phase, at T= 298.15 K, were derived. The results were analyzed and interpreted in terms of enthalpic increments and molecular structure. For comparison purposes, standard ab initio molecular calculations at the G3(MP2)//B3LYP level were performed, using a set of working reactions and the gas-phase enthalpies of formation of both compounds were estimated; the results are in excellent agreement with experimental data. The computational study was also extended to the determination of proton and electron affinities, basicities and adiabatic ionization enthalpies. [ABSTRACT FROM AUTHOR]

The present work reports the thermodynamic study performed on three monofluorinated nitrobenzene derivatives by a combination of experimental techniques and computational approaches. The standard (p° = 0.1 MPa) molar enthalpies of formation in the liquid phase of the three isomers of fluoronitrobenzene were derived from the standard molar energies of combustion, in oxygen, at T= 298.15 K, measured by rotating bomb combustion calorimetry. The vapor pressure study of the referred compounds was done by a static method and, from the obtained results, the phase diagrams were elaborated, and the respective triple point coordinates, as well as the standard molar enthalpies of vaporization, sublimation and fusion, at T= 298.15 K, were determined. The combination of some of the referred thermodynamic parameters yielded the standard (p° = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T= 298.15 K, of the studied compounds: ΔfHmo(2-fluoronitrobenzene, g) = −(102.4 ± 1.5) kJ·mol−1, ΔfHmo(3-fluoronitrobenzene, g) = −(128.0 ± 1.7) kJ·mol−1, and ΔfHmo(4-fluoronitrobenzene, g) = −(133.9 ± 1.4) kJ·mol−1. Using the empirical scheme developed by Cox, values of standard molar enthalpies of formation in the gaseous phase were estimated and afterwards compared with the ones obtained experimentally, and both were interpreted in terms of the molecular structure of the compounds. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. The computed values compare very well with the experimental results obtained in this work and show that 4-fluoronitrobenzene is the most stable isomer from the thermodynamic point of view. Furthermore, this composite approach was also used to obtain information about the gas-phase basicities, proton and electron affinities and, finally, adiabatic ionization enthalpies. [ABSTRACT FROM AUTHOR]

The relative stabilities of 2,2′- and 3,3′-bithiophenes were evaluated by experimental thermochemistry and the results compared with data obtained from state of the art calculations, which were also extended to 2,3′-bithiophene. The standard (p° = 0.1 MPa) molar enthalpies of formation of crystalline 2,2′-bithiophene and 3,3′-bithiophene were calculated from the standard molar energies of combustion, in oxygen, to yield CO2(g) and H2SO4·115H2O, measured by rotating-bomb combustion calorimetry at T= 298.15 K. The vapor pressures of these two compounds were measured as a function of temperature by Knudsen effusion mass-loss technique. The standard molar enthalpies of sublimation, at T= 298.15 K, were derived from the Clausius−Clapeyron equation. The experimental values were used to calculate the standard (p° = 0.1 MPa) enthalpies of formation of the title compounds in the gaseous phase; the results were analyzed and interpreted in terms of enthalpic increments and molecular structure. Standard ab initio molecular orbital calculations at the G3(MP2)//B3LYP level were performed. Enthalpies of formation, using homodesmotic reactions, were calculated and compared with experimental data. The computational study was also extended to the isomeric compound 2,3′-bithiophene. Detailed inspections of the molecular and electronic structures of the compounds studied were carried out. Finally, bond dissociation enthalpies (BDE) and enthalpies of formation of thienyl radicals were also computed. [ABSTRACT FROM AUTHOR]

Static bomb calorimetry, Calvet microcalorimetry and the Knudsen effusion technique were used to determine the standard molar enthalpy of formation in the gas phase, at T= 298.15 K, of the indole and indoline heterocyclic compounds. The values obtained were 164.3 ± 1.3 kJ·mol−1and 120.0 ± 2.9 kJ·mol−1, respectively. Several different computational approaches and different working reactions were used to estimate the gas-phase enthalpies of formation for indole and indoline. The computational approaches support the experimental results reported. The calculations were further extended to the determination of other properties such as bond dissociation enthalpies, gas-phase acidities, proton and electron affinities and ionization energies. The agreement between theoretical and experimental data for indole is very good supporting the data calculated for indoline. [ABSTRACT FROM AUTHOR]

The standard (p° 0.1 MPa) molar enthalpies of formation, %@mt;sys@%%@sb@%f%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@%, of crystalline 2-, 3- and 4-chlorobenzophenone and 4,4‘-dichlorobenzophenone were derived from the standard molar energies of combustion, %@mt;sys@%%@sb@%c%@sbx@%%@ital@%U%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@%, in oxygen, to yield CO2(g), N2(g), and HCl·600H2O(l), at T298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high-temperature vacuum sublimation technique was used to measure the enthalpy of sublimation, %@mt;sys@%%@sx@%cr%@be@%g%@sxx@%%@mx@%%@mt;sys@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@%, of the compound 2-chlorobenzophenone. For the other three compounds, the standard molar enthalpies of sublimation, at T298.15 K were derived by the Clausius−Clapeyron equation, from the temperature dependence of the vapor pressures of these compounds, measured by the Knudsen-effusion technique. From the values of %@mt;sys@%%@sb@%f%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@%and %@mt;sys@%%@sx@%cr%@be@%g%@sxx@%%@mx@%%@mt;sys@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@%, the standard molar enthalpies of formation of all the compounds, in the gaseous phase, %@mt;sys@%%@sb@%f%@sbx@%%@ital@%H%@rsf@%%@/xs;55;%lnwidth@%°%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%m%@sbx@%%@mx@%(g), at T298.15 K, were derived. These values were also calculated by using the B3LYP/6-311G(2d,2p)//B3LYP/6-31G(d) computational approach. [ABSTRACT FROM AUTHOR]

The standard (po0.1 MPa) molar enthalpies of formation in the condensed phase of seven isomers of fluoromethylaniline were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g), N2(g) and HF·10H2O(l), at T298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation of these compounds, also at T298.15 K, were determined using Calvet microcalorimetry, while the enthalpies of fusion of the solid compounds were determined by differential scanning calorimetry. The standard molar enthalpies of formation in the gaseous phase, at T298.15 K, were derived from the former two experimental quantities. G3MP2//B3LYP calculations were performed for all possible fluoromethylanilines allowing the estimation of data for the isomers that were not studied experimentally. The Cox scheme was applied with two different approaches for the estimation of the standard molar enthalpies of formation of all the isomers studied, and this led to the conclusion that the literature values for the enthalpies of formation of the metaand paraisomers of methylaniline seem to be not reliable. Further G3MP2//B3LYPs calculations on the methylaniline isomers yielded new values for the standard molar enthalpies of formation of the isomers of methylaniline, which have been tested under the Cox scheme, resulting in better estimates. [ABSTRACT FROM AUTHOR]

The standard (p° 0.1 MPa) molar enthalpies of formation in the condensed phase of all the fluoroanilines, with the exception of the 2,3,5-trifluoroaniline compound, were derived from the standard molar energies of combustion in oxygen at T298.15 K, measured by rotating bomb combustion calorimetry. Calvet high-temperature vacuum sublimation experiments were performed to measure their enthalpies of vaporization or sublimation. These experiments allowed the determination of the standard molar enthalpies of formation in the gaseous phase and at T298.15 K. These values are also compared with estimates based on G3MP2B3 and BP86/6-31G(d) computations, which have been extended also to the fluoroaniline that was not studied experimentally. The results are in close agreement with a mean deviation of ∼3 kJ·mol-1. The largest difference between experimental and G3MP2B3 values is found for the pentafluoroaniline (−7.0 kJ·mol-1). For the three monofluoroanilines, the composite approach has been used also to compute gas-phase acidities, electron and proton affinities, ionization enthalpies and N−H bond dissociation enthalpies. The computed values compare well with available experimental results supporting the new computed data. [ABSTRACT FROM AUTHOR]

The standard (p00.1 MPa) molar enthalpies of formation, f%@mt;sys@%%@ital@%H%@rsf@%%@sx@%M%@be@%0%@sxx@%%@mx@%, for liquid 2,4,6-trichloropyrimidine and for crystalline 2-chloropyrimidine, 2,4- and 4,6-dichloropyrimidine, and 2,4,5,6-tetrachloropyrimidine compounds were determined at T298.15 K by rotating-bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation, %@mt;sys@%%@sx@%cr,l%@be@%g%@sxx@%%@mx@%%@mt;sys@%%@ital@%H%@rsf@%%@sx@%M%@be@%0%@sxx@%%@mx@%, of these compounds at T298.15 K were determined by Calvet microcalorimetry. The experimental standard molar enthalpies of formation of those compounds, in the gaseous state, at T298.15 K, were thus obtained by combining these two sets of results. The latter values have been employed in the calibration of the computational procedure, which has been used to estimate the gas-phase enthalpies of formation for the other chloropyrimidines that were not possible to obtain in a pure form for the experimental study. It is found that the exchange-correlation functional based on the local spin density approximation (LSDA) seems to be a cheap choice for the estimation of enthalpies of formation for heterocycles containing nitrogen atoms; the well-known B3LYP hybrid method yields larger differences, with respect to the experimental values, for 2,4,6-tri- and 2,4,5,6-tetrachloropyrimidines. [ABSTRACT FROM AUTHOR]

The standard (po 0.1 MPa) molar enthalpies of formation of 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-dichloroanilines were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g), N2(g) and HCl·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 enthalpies of sublimation of the six isomers. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the six isomers of dichloroaniline, in the gaseous phase, at T 298.15 K. The gas-phase enthalpies of formation were also estimated by G3MP2B3 calculations, which were further extended to the computation of gas-phase acidities, proton affinities, and ionization enthalpies. [ABSTRACT FROM AUTHOR]