Static Bomb Combustion Calorimeter Research Articles

Experimental and computational thermochemical study of dimethoxyacetophenones

The standard (po = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, for 2′,4′-, 2′,5′-, 2′,6′- and 3′,4′-dimethoxyacetophenones, in the condensed phase, were derived from measurements of the standard massic energies of combustion using a static bomb combustion calorimeter. The standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, were determined by high temperature Calvet microcalorimetry. Combining the results measured by these two techniques, the standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived.Computational studies for the experimentally studied compounds were also performed, as a complement to the experimental work, being also extended to the 2′,3′- and 3′,5′-dimethoxyacetophenone isomers. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3 level.Group additivity values and corrections for functional group interactions in the benzene ring were derived and used for predicting enthalpies of formation for dimethoxyacetophenones. The applicability of simple group-additivity procedures to tri-substituted benzenes was discussed.

Gas-phase standard enthalpy of formation of 3,5-dimethyl-4-nitroisoxazole determined by semi-micro-combustion calorimetry and thermal analysis

The present paper reports the determination of the standard (p° = 0.1 MPa) molar enthalpy of formation in gas phase at T = 298.15 K of 3,5-dimethyl-4-nitroisoxazole, which was derived from the enthalpy of combustion in solid state and the sublimation enthalpy. The combustion enthalpy was derived from the respective combustion energy value, which was obtained from combustion calorimetry using a static bomb combustion calorimeter in oxygen atmosphere at T = 298.15 K. The sublimation enthalpy was obtained at the same temperature by using thermogravimetry experiments in isothermal regime. The purity and the constant pressure heat capacity of the compound were determined by using differential scanning calorimetry, priori to carry out the combustion experiments. The value obtained of formation enthalpy of compound in gas phase presents high precision and low uncertainty.

Calorimetric and computational studies for three nitroimidazole isomers

In the present work, a combined experimental and computational thermochemical study of nitroimidazole isomers was carried out. The standard (p°=0.1MPa) molar enthalpy of combustion, in the crystalline phase, for 4-nitroimidazole was determined, at the temperature of 298.15K, using a static bomb combustion calorimeter. Calvet microcalorimetry experiments were performed to measure its standard molar enthalpy of sublimation. The standard molar enthalpy of formation of 4-nitroimidazole, in the gaseous phase, at T=298.15K, (116.9±2.9)kJ·mol−1, has been derived from the corresponding standard molar enthalpy of formation in the crystalline phase and the standard molar enthalpy of sublimation.Computational studies for 4-nitroimidazole were performed to complement the experimental work. These were also extended to the 2- and 5-nitroimidazole isomers. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3 level. Also investigated were the tautomeric equilibrium of 4(5)-nitroimidazole in the gaseous phase and it was concluded that the two tautomers are equally stable.

Energy characteristics of nitrooxazolidines and their radicals

The standard molar enthalpies of combustion for three methyl and dimethyl nitrooxazolidine derivatives in the liquid and crystalline states were determined using a high-precision static bomb combustion calorimeter. The resulting values were used to derive the standard molar enthalpies of formation of the azidomethyl-N-nitrooxazolidines. The standard molar enthalpies of vaporization for these compounds were measured using a Calvet microcalorimeter. The enthalpies of formation of some nitrooxazolidine-derived radicals and biradicals were calculated.

Thermodynamic properties of alkyl 1H-indole carboxylate derivatives: A combined experimental and computational study

The standard (po=0.1MPa) molar enthalpies of formation, in the crystalline phase, of methyl 1H-indole-3-carboxylate and ethyl 1H-indole-2-carboxylate, at T=298.15K, were derived from measurements of the standard massic energies of combustion using a static bomb combustion calorimeter. The Knudsen effusion technique was used to measure the vapour pressures as a function of the temperature, which allowed determining the standard molar enthalpies of sublimation of these compounds. The standard (po=0.1MPa) molar enthalpies of formation, in the gaseous phase, at T=298.15K, were calculated by combining, for each compound, the standard molar enthalpy of formation, in the crystalline phase, and the standard molar enthalpy of sublimation, yielding −(207.6±3.6)kJ·mol−1 and −(234.4±2.4)kJ·mol−1, for methyl 1H-indole-3-carboxylate and ethyl 1H-indole-2-carboxylate, respectively.Quantum chemical studies were also conducted, in order to complement the experimental study. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3(MP2) level, for the compounds studied experimentally, extending the study to the methyl 1H-indole-2-carboxylate and ethyl 1H-indole-3-carboxylate. The results obtained were compared with the experimental data and were also analysed in terms of structural enthalpic group contributions.

Experimental and computational energetic study of 1-R-2-phenylindole (R = H, CH3, C2H5)

The standard (po=0.1MPa) molar energies of combustion, ΔcUmo, of 2-phenylindole, 1-methyl-2-phenylindole and 1-ethyl-2-phenylindole, in the crystalline state, were determined, at T=298.15K, using a static bomb combustion calorimeter. The vapour pressures as a function of the temperature for these compounds were measured by the Knudsen effusion technique and the standard molar enthalpies of sublimation were derived. From the experimental results, the standard (po=0.1MPa) molar enthalpies of formation in the condensed and gaseous phases, at T=298.15K, of 2-phenylindole, 1-methyl-2-phenylindole and 1-ethyl-2-phenylindole were calculated.Additionally, the gas-phase enthalpies of formation of these compounds and also for 1-ethylindole were estimated by G3(MP2) calculations. Enthalpies of formation, obtained using appropriate working reactions, were calculated and compared with the experimental data. The results were also analysed in terms of structural enthalpic group contributions.

Thermodynamic properties of 5-(1-adamantyl)tetrazole

Abstract Temperature dependence of the heat capacity of 5-(1-adamantyl)tetrazole was studied between (5 and 370) K in a vacuum adiabatic calorimeter. From obtained data the thermodynamic properties of the compound in the condensed state were evaluated over the range of (0–370) K. The crystal structure of 5-(1-adamantyl)tetrazole was determined from the X-ray diffraction analysis. The saturated vapor pressure for crystalline 5-(1-adamantyl)tetrazole in the temperature ranges from (394 to 419) K was measured by the Knudsen effusion method, and its enthalpy of sublimation was obtained using these results. The standard enthalpy of formation for crystalline 5-(1-adamantyl)tetrazole at 298.15 K was determined in a static bomb combustion calorimeter. From these data, the standard enthalpy of formation for gaseous 5-(1-adamantyl)tetrazole was evaluated. The enthalpy of formation calculated using quantum chemical methods is in an excellent agreement with the experimental value. The thermodynamic properties of 5-(1-adamantyl)tetrazole in the ideal-gas state were calculated in the temperature range from (0 to 1000) K. The calculated entropy of gaseous 5-(1-adamantyl)tetrazole is in a good agreement with the one obtained from the experimental data.

The standard molar enthalpies of combustion and formation of 2-methylbenzothiazole, 2-methylbenzoxazole, and 2-methyl-2-thiazoline

A static-bomb combustion calorimeter and a rotating-bomb combustion calorimeter were used to determine the energies of combustion of 2-methylbenzothiazole, 2-methylbenzoxazole, and 2-methyl-2-thiazoline. The static- and rotating-bomb calorimeters were recently calibrated by the standard benzoic acid combustion runs and they were tested with adequate secondary combustion standards. The rotating-bomb calorimeter was tested using thianthrene and, in the present work, 1,2,4-triazole was used to test the static-bomb calorimeter. From the energies of combustion of the compounds under study, the liquid-phase standard molar enthalpies of formation were derived, at T = 298.15 K, as: (72.5 ± 1.5), (−50.7 ± 2.1), and (−88.5 ± 2.8) kJ mol−1, respectively.

Experimental study on the energetics of two indole derivatives

The standard (p o = 0.1 MPa) molar energies of combustion, $$ \Updelta_{\text{c}} H_{\text{m}}^{\text{o}} $$ , for indole-2-carboxylic acid and indole-3-carboxaldehyde, in the crystalline state, were determined, at T = 298.15 K, using a static bomb combustion calorimeter. For both compounds, the vapour pressures as function of temperature were measured, by the Knudsen effusion technique, and the standard molar enthalpies of sublimation, $$ \Updelta_{\text{cr}}^{\text{g}} H_{\text{m}}^{\text{o}} $$ , at T = 298.15 K, were derived by the Clausius–Clapeyron equation. From the experimental results, the standard (p o = 0.1 MPa) molar enthalpies of formation in the condensed and gaseous phases, at T = 298.15 K, of indole-2-carboxylic acid and indole-3-carboxaldehyde were derived. The results are analysed in terms of structural enthalpic increments.

Enthalpies of formation of 5,6-dihydro-5-methyluracil and 5,6-dihydro-6-methyluracil

The standard (p°=0.1MPa) molar enthalpy of combustion, ΔcHm°, of two crystalline compounds, 5,6-dihydro-5-methyluracil and 5,6-dihydro-6-methyluracil, were determined, at T=298.15K, using a static bomb combustion calorimeter. The vapor pressures as a function of the temperature were measured for those compounds, by the Knudsen effusion technique, and the standard molar enthalpies of sublimation at the mean temperature of the vapor pressure measurements were derived from the Clausius–Clapeyron equation, and corrected to T=298.15K using an estimated value for ΔcrgCp,m°. These values were used to derive the standard molar enthalpies of formation of the two compounds studied, in the condensed and gaseous phases. Some considerations about the relative stability of the two isomers were made and compared with similar compounds.

Thermodynamic properties of 1-ethyl-4-nitro-1,2,3-triazole

Temperature dependence of the heat capacity and the parameters of phase transitions of 1-ethyl-4-nitro-1,2,3-triazole (1ET) were studied between 5 and 370K in a vacuum adiabatic calorimeter. Thermodynamic properties of the 1ET in the condensed state were obtained over the range of 0–370K. Saturated vapor pressure for crystalline 1ET in the temperature ranges from 313 to 344K and its enthalpy of sublimation were measured by the Knudsen effusion method. The standard enthalpy of formation for crystalline 1ET at 298.15K was determined in a static bomb combustion calorimeter. From these data, the standard enthalpy of formation for gaseous 1ET was evaluated. The enthalpy of formation calculated using quantum chemical methods is in excellent agreement with the experimental value.

Experimental study on the thermochemistry of some amino derivatives of uracil

Values of the standard (p∘=0.1MPa) molar enthalpy of combustion, ΔcHm∘, of four crystalline compounds: 5-aminouracil, 6-aminouracil, 6-amino-1-methyluracil, and 6-amino-1,3-dimethyluracil, were determined, at T=298.15K, using a static bomb combustion calorimeter. The values obtained of standard molar enthalpy of combustion were used to derive the standard molar enthalpy of formation of the compounds investigated in their condensed phase and together with literature values of the standard molar enthalpy of sublimation, yielded the standard molar enthalpies of formation in the gaseous phase. These are discussed in terms of the effects of the molecular structure on the relative enthalpic stability.

An Isoperibolic Micro-Bomb Combustion Calorimeter of Low Cost for Measurement of the Enthalpy of Combustion: Chemical Calibration

A micro static-bomb combustion calorimeter has been developed in our laboratory designing one small cell to obtain combustion heats, which requires only a smaller sample quantity. The energy equivalent of the combustion system has been provided with a new micro-bomb. In the best conditions of operation, the energy equivalent of this calorimetric arrangement is just (calor)= (1,1679 ± 0,0004) kJK-1, which means an uncertainty of 0,03% for the calibration with benzoic acid NIST 39 Joule. This combustion calorimeter has been used in the measurement of the enthalpy of combustion of m-methoxybenzoic acid and salicylic acid, giving (-24,21876 ± 0,00102) kJg-1 and (-21,0078 ± 0,0025) kJg-1, respectively, for these substances. Keywords: Benzoic acid, m-methoxybenzoic acid, micro-combustion calorimetry, enthalpy of combustion, energy of combustion, isoperibolic micro-bomb, thermodynamic study, calorimeter, arc system, thremostat, Combustion, indium, ignition, salicylic acid

Experimental study on the thermochemistry of 3-nitrobenzophenone, 4-nitrobenzophenone and 3,3′-dinitrobenzophenone

The standard ( p° = 0.1 MPa) molar enthalpies of combustion, Δ c H m ∘ , for the 3- and 4-nitrobenzophenones and for the 3,3′-dinitrobenzophenone, in the crystalline state, were determined, at the temperature T = 298.15 K, using a static bomb combustion calorimeter. For these compounds, the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K, were determined by Calvet microcalorimetry. For the 3- and 4-nitrobenzophenones the vapour pressures as function of temperature were measured by the Knudsen effusion technique and the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K, were derived by the Clausius–Clapeyron equation. The results are as follows: - Δ c H m ∘ ( cr ) / ( kJ · mol - 1 ) Δ cr g H m ∘ / ( kJ · mol - 1 ) Calvet Knudsen 3-Nitrobenzophenone 6324.5 ± 1.4 123.3 ± 2.4 121.6 ± 0.6 4-Nitrobenzophenone 6327.8 ± 1.9 122.3 ± 2.7 122.9 ± 0.7 3,3′-Dinitrobenzophenone 6154.6 ± 2.2 147.4 ± 3.9 These values were used to derive the standard molar enthalpies of formation of the compounds in their condensed and gaseous phases, respectively. For 3- and 4-nitrobenzophenones, the standard ( p° = 0.1 MPa) molar enthalpies, entropies and Gibbs functions of sublimation, at T = 298.15 K, were derived. The derived standard molar enthalpies of formation in the gaseous state are analysed in terms of structural enthalpic increments.

Thermodynamics of Ethyl Decanoate

The heat capacity of ethyl decanoate in the interval of (5 to 370) K was measured in an adiabatic calorimeter. The triple-point temperature Tfus = (253.60 ± 0.02) K and the enthalpy of fusion ΔcrliqHm° = (32.29 ± 0.04) kJ·mol−1 were determined. The vapor pressure over liquid ethyl decanoate in the interval of (294 to 323) K was measured by the Knudsen method. The calorimetric enthalpy of vaporization ΔliqgHm°(304.8 K) = (69.9 ± 0.7) kJ·mol−1 was determined in an MID-200 Calvet-type microcalorimeter. The standard enthalpy of formation for liquid ethyl decanoate at 298.15 K ΔfHm°(liq) = (−682.7 ± 2.4) kJ·mol−1 was determined in a static bomb combustion calorimeter. From these data, the standard enthalpy of formation for gaseous ethyl decanoate was evaluated to be ΔfHm°(g) = (−612.2 ± 2.4) kJ·mol−1. The formation enthalpy was also calculated using quantum chemical methods via homodesmic reactions at different theory levels. The results are in excellent agreement with the experimental value.

Standard molar enthalpies of formation of some vinylfuran derivatives

The standard ( p ∘ = 0.1 MPa) molar enthalpies of combustion, Δ c H m ∘ , for crystalline 2-furanacrylic acid, 3-furanacrylic acid, and 3-(2-furyl)-2-propenal and for the liquid 2-furanacrylonitrile were determined, at the temperature 298.15 K, using a static bomb combustion calorimeter. For these compounds, the standard molar enthalpies of phase transition, Δ cr,l g H m ∘ , at T = 298.15 K, were determined by Calvet microcalorimetry. For the two crystalline furanacrylic acids the vapour pressures as function of temperature were measured by the Knudsen effusion technique and the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K were derived by the Clausius–Clapeyron equation. The results are as follows: - Δ c H m ∘ ( cr,l ) / ( kJ · mol - 1 ) Δ cr,l g H m ∘ / ( kJ · mol - 1 ) Calvet Knudsen 2-Furanacrylic acid (cr) 3149.8 ± 0.5 103.0 ± 0.7 103.3 ± 0.5 3-Furanacrylic acid (cr) 3151.5 ± 0.7 104.9 ± 1.1 106.8 ± 0.5 3-(2-Furyl)-2-propenal (cr) 3425.7 ± 1.2 82.3 ± 0.4 2-Furanacrylonitrile (l) 3562.5 ± 1.3 65.2 ± 0.6 These values were used to derive the standard molar enthalpies of formation of the compounds in their condensed and gaseous phases, respectively. For 2-furanacrylic acid and 3-furanacrylic acid, the standard ( p ∘ = 0.1 MPa) molar enthalpies, entropies, and Gibbs functions of sublimation, at T = 298.15 K, were derived. The derived standard molar enthalpies of formation in the gaseous state are analysed in terms of structural enthalpic increments.

Thermochemistry of nitronaphthalenes and nitroanthracenes

The standard ( p ∘ = 0.1 MPa) molar energies of combustion, Δ c U m ∘ , for crystalline 1-nitronaphthalene and 9-nitroanthracene were determined, at the temperature 298.15 K, using a static bomb combustion calorimeter. For these compounds, the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K, were derived by the Clausius–Clapeyron equation, from the temperature dependence of the vapour pressures of these compounds, measured by the Knudsen effusion technique. The results were as follows: - Δ c U m ∘ ( cr ) Δ cr g H m ∘ kJ · mol −1 kJ · mol −1 1-Nitronaphthalene 4984.8 ± 1.4 95.1 ± 0.4 9-Nitroanthracene 6905.0 ± 2.8 111.4 ± 0.6 These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. 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. Using estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds, the standard ( p ∘ = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived. Additionally, standard enthalpies of formation for these two compounds were estimated by computations based on density functional theory. The estimated values are in excellent agreement with experimental data, which gives support to the estimates based on computational thermochemistry for the gas-phase enthalpies of formation of 2-nitronaphthalene, 1-nitroanthracene and 2-nitroanthracene.

Thermochemistry of some alkylsubstituted anthracenes

The standard ( p ∘ = 0.1 MPa) molar enthalpies of combustion, Δ c H m ∘ , for crystalline 9-methylanthracene, 2-ethylanthracene, and 9,10-dimethylanthracene were determined, at the temperature 298.15 K, using a static bomb combustion calorimeter. For these compounds, the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K were derived by the Clausius-Clapeyron equation, from the temperature dependence of the vapour pressures of these compounds, measured by the Knudsen-effusion technique. The results were as follows: - Δ c H m ∘ ( cr ) / ( kJ · mol - 1 ) Δ cr g H m ∘ / ( kJ · mol - 1 ) 9-Methylanthracene 7714.7 ± 3.4 101.8 ± 1.0 2-Ethylanthracene 8357.3 ± 3.2 107.6 ± 0.6 9,10-Dimethylanthracene 8367.2 ± 3.8 113.0 ± 1.7 These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. 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. Using estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds, the standard ( p ∘ = 0.1 MPa) molar enthalpies, entropies, and Gibbs energy of sublimation, at T = 298.15 K, were derived. Additionally, standard enthalpies of formation were estimated by computations based on density-functional theory. The estimated values are in excellent agreement with experimental data.

Enthalpies of combustion and formation of fullerene C 70 by isoperibolic combustion calorimetry

A micro static-bomb combustion calorimeter developed from a 1107 Parr semi-micro bomb, has been used for the measurement of the enthalpy of combustion of the fullerene C 70, yielding Δ c U o m (cr, T=298.15 K)=−(30099.7 ± 56.9) kJ · mol −1. The enthalpy of formation in the gas phase is derived from the experimental results and from literature data. The calculation of the enthalpy of formation by carbon atom, the strain energy, and the bond enthalpies give insight about the stability of each fullerene.

Low-temperature heat capacities and standard molar enthalpy of formation of aspirin

Molar heat capacities (Cp,m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of Cp,mvs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding function is as follows: for 78 K≤T≤383 K, Cp,m/J mol-1 K-1=19.086X4+15.951X3-5.2548X2+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {ΔHT -ΔH298.15} and {ST-S298.15}, were derived. Combustion energy of aspirin (ΔcUm) was determined by static bomb combustion calorimeter. Enthalpy of combustion (ΔcHom) and enthalpy of formation (ΔfHom) were derived through ΔcUm as - (3945.26±2.63) kJ mol-1 and - (736.41±1.30) kJ mol-1, respectively.