Maria Victoria Roux

Critically evaluated thermochemical properties of polycyclic aromatic hydrocarbons

Experimental thermochemical properties of benzene, toluene, and 63 polycyclic aromatic hydrocarbons, published within the period 1878–2008 (over 350 references), are reported. Available experimental data for the enthalpies of combustion used to calculate enthalpies of formation in the condensed state, combined with sublimation, vaporization, and fusion enthalpies, are critically evaluated. Whenever possible, recommended values for these thermochemical properties and for the enthalpies of formation in the gas state at T=298.15K are provided.

Thermochemical properties of N-heterocyclic compounds I. Enthalpies of combustion, vapour pressures and enthalpies of sublimation, and enthalpies of formation of pyrazole, imidazole, indazole, and benzimidazole

Abstract The energies of combustion of pyrazole, imidazole, indazole, and benzimidazole have been determined using a static bomb calorimeter. The vapour pressures have been measured over a temperature range of about 20 K by the Knudsen-effusion technique. From the experimental results the following quantities for the four compounds at 298.15 K have been derived: Compound Δ f H m o (cr)/(kJ · mol −1 ) Δ sub H m o /(kJ · mol −1 ) Δ f H m o (g)/(kJ · mol −1 ) Pyrazole 105.4±0.7 74.0±0.4 179.4±0.8 Imidazole 49.8±0.6 83.1±0.2 132.9±0.6 Indazole 151.9±1.3 91.1±0.2 243.0±1.3 Benzimidazole 79.5±1.3 102.2±0.4 181.7±1.4

Thermochemical properties of N-heterocyclic compounds II. Enthalpies of combustion, vapour pressures, enthalpies of sublimation, and enthalpies of formation of 1,2,4-triazole and benzotriazole

Abstract The energies of combustion of 1,2,4-triazole and benzotriazole have been determined using a static bomb calorimeter. The vapour pressures have been measured over a temperature range of about 15 K by the Knudsen effusion technique. From the experimental results the following quantities for the two compounds at 298.15 K have been derived: Compound Δ f H m o (cr) Δ sub H m o Δ f H m o (g) kJ · mol −1 kJ · mol −1 kJ · mol −1 1,2,4-Triazole 108.7±0.4 84.0±0.7 192.7±0.8 Benzotriazole 236.5±1.2 99.0±0.5 335.5±1.3

Structure-Energy Relationship in Barbituric Acid: A Calorimetric, Computational, and Crystallographic Study

This paper reports the value of the standard (p(o) = 0.1 MPa) molar enthalpy of formation in the gas phase at T = 298.15 K for barbituric acid. The enthalpies of combustion and sublimation were measured by static bomb combustion calorimetry and transference (transpiration) method in a saturated N2 stream and a gas-phase enthalpy of formation value of -(534.3 +/- 1.7) kJ x mol(-1) was determined at T = 298.15 K. G3-calculated enthalpies of formation are in very good agreement with the experimental value. The behavior of the sample as a function of the temperature was studied by differential scanning calorimetry, and a new polymorph of barbituric acid at high temperature was found. In the solid state, two anhydrous forms are known displaying two out of the six hydrogen-bonding patterns observed in the alkyl/alkenyl derivatives retrieved from the Cambridge Crystallographic Database. The stability of these motifs has been analyzed by theoretical calculations. X-ray powder diffraction technique was used to establish to which polymorphic form corresponds to the commercial sample used in this study and to characterize the new form at high temperature.

Thermochemical properties of naphthalene compounds II. Enthalpies of combustion and formation of the 1- and 2-naphthols

Abstract The energies of combustion of 1-naphthoic and 2-naphthoic acids were determined using a static bomb calorimeter. The sublimation vapour pressures were measured in a given temperature range by the Knudsen effusion technique. The formation enthalpies in the crystalline state at 298.15 K and the sublimation enthalpies at the mean temperature of the measurement ranges were derived for the two acids. The values obtained are: −ΔH° f ( c ) kcal th mol −1 −ΔH s kcal th mol −1 1-naphthoic acid 79.71 ± 0.25 −26.38 ± 0.05 (at 350.5 K) 2-naphthoic acid 82.71 ± 0.35 −27.15 ± 0.19 (at 355.6 K) The results are discussed in terms of steric effects arising from the carboxylic group.

Evaluation of poultry litter as a feasible fuel

Caloric values (massic energy of combustion) of poultry litter coming from the chicken farm “Cantos Blancos” (Guadalajara– Spain) were determined by static bomb calorimetry. These values correspond to samples treated in different conditions of drying-up. The massic energy of combustion of the “dry samples” was 14 447 kJ/kg and for “wet samples” decreased linearly with increasing water content. The optimum conditions to use these waste product as an economic fuel were also established.

Thermochemical properties of N-heterocyclic compounds III. Enthalpies of combustion, vapour pressures and enthalpies of sublimation, and enthalpies of formation of 9H-carbazole, 9-methylcarbazole, and 9-ethylcarbazole

Abstract The energies of combusion of 9H-carbazole, 9-methylcarbazole, and 9-ethylcarbazole have been measured using a static bomb calorimeter. The vapour pressures have been determined over a temperature range of about 15 K by the Knudsen-effusion technique. From the experimental results the following quantities for the three compounds at 298.15 K have been derived: Δ f H m o (cr) Δ sub H m o Δ f H m o (g) Compound kJ · mol−1 kJ · mol−1 kJ · mol1 9H-Carbazole 101.7±2.8 103.3±1.1 205.0±3.0 9-Methylcarbazole 103.7±2.4 95.5±0.3 199.2±2.4 9-Ethylcarbazole 70.6±2.6 99.1±0.3 169.7±2.6

Experimental and computational thermochemical study of α-alanine (DL) and β-alanine.

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, Δ(f)H(m)°(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.

Structural effects on the thermochemical properties of carbonyl compounds I. Enthalpies of combustion, vapour pressures and enthalpies of sublimation, and enthalpies of formation of 2-methylpropanamide, 2,2-dimethylpropanamide, and 1-adamantyl carboxamide

Abstract The energies of combustion of 2-methylpropanamide, 2,2-dimethylpropanamide, and 1-adamantyl carboxamide have been determined using a static bomb calorimeter. The vapour pressures have been measured over a temperature range of about 15 K by the Knudsen-effusion technique. From the experimental results the following quantities for the three compounds, at 298.15 K, have been derived: Compound Δ f H m o (cr) Δ sub H m o Δ f H m o (g) kJ·mol −1 kJ·mol −1 kJ·mol −1 2-Methylpropanamide −368.6 ± 0.9 86.0 ± 0.2 −282.6 ± 0.9 2,2-Dimethylpropanamide −399.7 ± 1.3 86.6 ± 0.4 −313.1 ± 1.4 1-Adamantyl carboxamide −427.0 ± 2.4 108.0 ± 0.5 −319.0 ± 2.5 The structural effects on the thermochemical properties have been studied.

Experimental and theoretical study of the structures and enthalpies of formation of 3H-1,3-benzoxazole-2-thione, 3H-1,3-benzothiazole-2-thione, and their tautomers.

This paper reports an experimental and theoretical study of the structures and standard (p(o) = 0.1 MPa) molar enthalpies of formation of 3H-1,3-benzoxazole-2-thione and 3H-1,3-benzothiazole-2-thione. The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry and the Knudsen effusion technique, and gas-phase enthalpies of formation values at T = 298.15 K of (42.0 +/- 2.7) and (205.5 +/- 3.8) kJ x mol(-1) for 3H-1,3-benzoxazole-2-thione and 3H-1,3-benzothiazole-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in excellent agreement with the experimental values. The present work discusses the question of tautomerism explicitly for both compounds and compares the energetics of all the related species. A comparison of the theoretical results with the structural data is also reported.