Molar Enthalpies Of Combustion Research Articles

Thermochemical study of 2-adamantanone

The results of a thermochemical study of the standard molar enthalpy of combustion of 2-adamantanone in the crystalline phase state by isoperibol combustion calorimetry are presented. Two different approaches of combustion-calorimetry data processing (one from 1956 traditionally used in the field and another from 2021 updated with respect to equations and reference values) were compared and shown to give nearly indistinguishable results for 2-adamantanone (composed of only C, H, O elements). The results allowed resolving the observed inconsistency in the literature values of the enthalpy of formation of 2-adamantanone in the crystalline phase state published to date. The experimental standard enthalpy of formation for crystal was combined with the enthalpy of sublimation available in the literature to give the enthalpy of formation for gas, which is in excellent agreement with the gas-phase enthalpy of formation computed according to one of the most reliable quantum-chemical protocols. The enthalpy effect of the substitution of a methylene fragment with a carbonyl group was analyzed in a series of linear, branched, and cyclic alkanes. The evaluated effect indirectly confirms the absence of any measurable strain in 2-adamantanone in comparison to the parent molecule of adamantane.

Biofuels energetics: Measurements and evaluation of calorific values of triglycerides

The triglycerides with the saturated alkyl chains containing 3, 4, and 6 carbon atoms, as renewable energy sources were investigated. Specific energies of combustion were measured by using high-precision combustion calorimetry. The standard molar enthalpies of combustion and formation were derived from these results. Validation of the new calorific data for triglycerides was performed using the structure-property relationships. The experimental and additive enthalpies of formation for triglycerides measured in this work agree well and could be recommended for the thermochemical calculations for triglyceride technologies.

Synthesis, thermodynamic properties and Hirshfeld surface analysis of 2-[(4-methyl-benzoyl)-hydrazone]-propionic acid

A Schiff base compound, C11H12O3N2 (1), was synthesized and structurally characterized. The standard molar enthalpy of combustion and formation of 1 at T = 298.15 K and P = 0.1 MPa were determined to be ΔcHm˚(C11H12O3N2, s) = - (4989.91 ± 2.66) kJ·mol−1 and ΔfHm˚(C11H12O3N2, s) = -(1053.68 ± 7.79) kJ·mol−1, respectively. The low-temperature heat capacities of 1 were experimentally investigated at temperatures of 78–400 K. The Cp, m vs. T curve is smoothly ascending, no anomaly, which indicates that the structure of 1 is stable and no phase transition occurs during the whole test temperature range. The corresponding thermodynamic functions of 1 were calculated based on the smoothed heat capacities. Furthermore, in order to explore the distribution of weak intermolecular interactions within hydrate 1·H2O, the Hirshfeld surface and associated fingerprint plots were analyzed.

Low-temperature heat capacities, standard molar enthalpies of formation and detonation performance of two CL-20 cocrystal energetic materials

Two cocrystals of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) with 2,4,6-trinitrotoluene (TNT) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were prepared by a solvent/non-solvent (acetonitrile/distilled water) method at room temperature. The low-temperature heat capacities of CL-20∙TNT cocrystal and 2CL-20·HMX cocrystal were measured in the temperature range from 1.9 to 300 K using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). By fitting the heat capacity data to a series of theoretical and empirical models, the thermodynamic functions were derived. In addition, the standard molar heat capacities, entropies and enthalpies of cocrystal samples at 298.15 K and 0.1 MPa were also obtained. The standard molar energies of combustion of CL-20, TNT, HMX, CL-20∙TNT cocrystal, and 2CL-20·HMX cocrystal were determined. From the combustion results, the standard molar enthalpies of combustion and formation for the compounds at T = 298.15 K were derived. The detonation velocity (D) and detonation pressure (P) were obtained by Kamlet-Jacobs equations. 2CL-20·HMX cocrystal shows superior detonation velocity and detonation pressure, which are higher than those of CL-20∙TNT cocrystal.

Synthesis, crystal structure and thermal behavior of Bis(3,4-diaminofurazan)methane

A new energetic compound bis(3,4-diaminofurazan)methane (BDAFM) was synthesized and structurally characterized by X-ray diffraction. Theoretical calculation on BDAFM was carried out by B3LYP with 6-311+G(d) basis set. The crystal of BDAFM belongs to orthorhombic system with space group Pnn2. The BDAFM molecule is composed of two diaminofurazan groups linked by a methylene group, and the two diaminofurazan groups are centrosymmetric about the central C1 atom. Thermal decomposition of BDAFM was studied by DSC and TG/DTG methods. Results show that the thermal behavior of BDAFM presents a continuous melting-decomposition process, and the peak temperatures of melting and thermal decomposition are 251.8 and 276.4 °C, respectively. The molar heat capacity of BDAFM was determined as 245.7 J mol−1 K−1 at 298.15 K. The standard molar enthalpy of combustion and enthalpy of formation were obtained as −3362 and 259 kJ mol−1, respectively. The impact sensitivity of BDAFM is > 12.5 J, which is higher than that of DAF (>23.5 J) but lower than that of RDX and HMX (>7.4 J). The detonation velocity (D) and detonation pressure (P) for BDAFM were 7629 m s−1 and 24.38 GPa respectively, which are higher than that of TNT and close to that of DAAF.

Thermodynamic properties of some isomeric 5-(nitrophenyl)-furyl-2 derivatives

BackgroundThe aim of the current work was to determine thermodynamical properties of 5-(nitrophenyl)-2-furaldehyde oximes and 3-[5-(nitrolphenyl)-2-furyl]acrylic acids.ResultsThe temperature dependences of saturated vapor pressures of 5-(nitrophenyl)-2-furaldehyde oximes and 3-[5-(nitrolphenyl)-2-furyl]acrylic acids were determined by the Knudsen effusion method. The results are presented by the Clapeyron–Clausius equation in linear form, and via this form, the standard enthalpies of sublimation of compounds were calculated at 298.15 K. The standard molar formation enthalpies of compounds in crystalline state at 298.15 K were determined indirectly from the corresponding standard molar combustion enthalpy, obtained using combustion bomb calorimetry. The non-nearest neighbour interactions (strain) in molecule were defined. The ideal-gas enthalpies of investigated compounds formation and the data available from the literature were used for calculation of group-additivity parameters and the correction terms useful in the application of the Benson correlation.ConclusionDetermining the thermodynamic properties for these compounds will contribute to solving practical problems pertaining to optimization processes of their synthesis, purification and application. It will also provide a more thorough insight regarding the theoretical knowledge of their nature and are necessary for the application of the Benson group-contribution correlation for calculation of Delta {}_{f}H_{{m(298.15{text{K}})}}^{o} (g)calc.

Empirically Corrected Electronic Structure Calculations Applied to the Enthalpy of Combustion Physical Chemistry Laboratory

A method for using electronic structure calculations to predict the standard molar enthalpy of combustion for hydrocarbons is presented. In this approach, simple geometry optimizations can be used ...

Synthesis of Ethyl-4-ethoxy Pentanoate by Reductive Etherification of Ethyl Levulinate in Ethanol on Pd/SiO2 -C Catalysts.

The synthesis of biomass-derived ethers to be used as biofuels or biofuel additives has attracted much attention. Following the recently reported synthesis of etherified ester ethyl-4-ethoxy pentanoate (EEP) from γ-valerolactone (GVL) in ethanol catalyzed by H-beta zeolite, an alternative route to prepare EEP in high yield has been developed by reductive etherification of ethyl levulinate (EL) in ethanol at 140 °C under 0.5 MPa H2 with a silica-modified Pd/C catalyst. The ether production likely follows a tandem acetalization-hydrogenolysis process with ethyl-4,4-diethoxy pentanoate (EDEP) as the intermediate. The acetalization step can be favored by introducing acidic materials, such as SiO2 -carbon or beta zeolite, as a cocatalyst. The combination of the Pd/SiO2 -C and beta zeolite mixture leads to 100 % EL conversion and 93 % EEP selectivity under optimized reaction conditions. For the first time, the standard molar combustion enthalpy of as-prepared EEP is measured by using a static oxygen bomb, and the value of which is determined to be about -5658 kJ mol-1 , which is much larger than that of GVL (-2650 kJ mol-1 ).

Standard molar enthalpies of formation and phase changes of Tetra-N-phenylbenzidine and 4,4′-Bis (N-carbazolyl)-1,1′-biphenyl

The values of the standard molar energies of combustion of Tetra-N-phenylbenzidine and 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl in solid phase were obtained experimentally using an isoperibolic semi-micro combustion calorimeter. The calorimeter was calibrated with benzoic acid NIST 39j and tested with 1,2,4-triazole. The molar enthalpies of combustion in oxygen, at T = 298.15 K and po = 0.1 MPa were (− 18,522.4 ± 12.1) and (− 18,114.4 ± 12.5) kJ mol−1, respectively. The corresponding standard molar enthalpies of formation were derived as: (354.4 ± 12.9) and (518.1 ± 13.4) kJ mol−1. The vaporization enthalpies of the compounds were obtained by thermogravimetry, and these values were used to derive the enthalpies of formation in gaseous phase.

Standard molar enthalpies of formation for crystalline vanillic acid, methyl vanillate and acetovanillone by bomb calorimetry method

The massic energies of combustion for three crystalline monosubstituted guaiacols such as vanillic acid, methyl vanillate and acetovanillone were determined by using bomb calorimeter method and were found to be − (21,070.3 ± 8.6), − (23,352.3 ± 7.4) and − (26,732.2 ± 5.2) J g−1, respectively. The standard molar enthalpy of combustion and standard molar enthalpy of formation in the crystalline state at 298.15 K were calculated. They are − (3542.9 ± 1.5) and − (748.5 ± 1.8) kJ mol−1 for vanillic acid, − (4255.4 ± 1.7) and − (715.3 ± 2.1) kJ mol−1 for methyl vanillate, − (4444.7 ± 0.9) and − (526.1 ± 1.5) kJ mol−1 for acetovanillone, respectively. The basic contribution in a value of standard molar enthalpy of formation for oxygen-containing aromatic compounds provides the replacement of the hydrogen atom in the benzene ring to the oxygen-containing group. The calculation of these contributions gives the following values for the crystalline state at 298.15 K for substituents CHO − (150 ± 6), COCH3 − (201 ± 4), COOCH3 − (392 ± 6) and COOH − (428 ± 4) kJ mol−1. The differences in contributions for crystalline and gaseous states were estimated for groups CHO, COOCH3, COCH3 − (26 ± 3) kJ mol−1 in monosubstitute benzene derivatives, 4-substituted anisoles and guaiacols, − (35 ± 4) kJ mol−1 in 4-substituted phenols and for group COOH − (50 ± 3) kJ mol−1 in all abovementioned groups of compounds. More higher differences in contributions found for 4-substituted phenols and benzenecarboxylic acids are attributed to the hydrogen bonds formation in crystalline state of these derivatives.

Investigation on enthalpies of combustion and heat capacities for 2-aminomethylpyridine derivatives

The molar energies of combustion $$\left( {\Delta_{\text{c}} U_{\text{m}} } \right)$$ for 2-aminomethylpyridine (AMP), tert-butyl 2-[N-(tert-Y)-2-picolyamino]acetate (AMPY), N,N-dioctyl-2-(aminomethyl)pyridine (AMPO), and tert-butyl 2-(N-octyl-2-picolyamino)acetate (AMPA) were measured by an oxygen bomb calorimeter at 298.15 K, and the results are: − (3585.5 ± 2.4) kJ mol−1, − (10145.0 ± 7.2) kJ mol−1, − (14047.1 ± 18.8) kJ mol−1, − (12141.3 + 12.3) kJ mol−1, respectively. The standard molar enthalpies of combustion $$\left( {\Delta_{\text{c}} H_{\text{m}}^{\varTheta } } \right)$$ and standard molar enthalpies of formation $$\left( {\Delta_{\text{f}} H_{\text{m}}^{\varTheta } } \right)$$ for these compounds were derived from the experimental results and literature values. The values of $$\Delta_{\text{f}} H_{\text{m}}^{\varTheta }$$ for AMP, AMPY, AMPO and AMPA are 88.4 ± 2.5 kJ mol−1, − (930.4 ± 7.6)kJ mol−1, − (304.8 ± 19.0)kJ mol−1 and − (569.9 ± 12.6) kJ mol−1. The heat capacities at constant pressure for these compounds were measured with a DSC over the temperature range from 280 to 323 K, and the relationships between the heat capacity and temperature were obtained from measured results. The melting point and enthalpy of fusion for AMPY were also determined by DSC.

Investigation on standard molar enthalpy of combustion, specific heat capacity and thermal behavior of methionine

The standard molar enthalpy of combustion of methionine was determined to be − 6661.03 kJ mol−1 by XRY-1C microcomputer oxygen bomb calorimeter. The standard molar enthalpy of formation was calculated to be 3121.35 kJ mol−1 based on the standard molar combustion enthalpy. The thermal stability behavior of methionine was studied by the thermal gravimetric analysis. The results show that melting process of methionine was accompanied by the decomposition reaction in the temperature range of 500.15–520.15 K, displayed one-stage decomposition process. The absorb heat of methionine was obtained to be 974.34 kJ mol−1 (6530.00 J g−1) at 550.51 K by DSC-60 differential scanning calorimetry. Moreover, the specific heat capacity of methionine from 373.15 to 453.15 K in the solid state was measured, and then the relationship between the constant pressure specific heat capacity Cp and the temperature has been established. These data provide a thermodynamic basis for process development, engineering design and industrial production of methionine.

Experimental and computational thermochemical studies of acridone and N-methylacridone

Abstract This paper reports the standard (p° = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of acridone and N-methylacridone as (50.0 ± 5.0) kJ·mol−1 and (60.6 ± 4.3) kJ·mol−1, respectively. These data were obtained from experimental thermodynamic parameters, namely the standard molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, derived from the standard molar enthalpies of combustion measured by static-bomb combustion calorimetry, and the standard molar enthalpies of sublimation, at T = 298.15 K, determined by Calvet microcalorimetry or the Knudsen effusion techniques. Additionally, the gas-phase enthalpies of formation were estimated by G3(MP2)//B3LYP calculations, using several hypothetical gas-phase reactions, and were compared with the corresponding ones determined experimentally. The gas-phase keto-enol tautomerization chemical equilibrium of acridone ↔ 9-acridinol was analysed using the Boltzmann’s distribution, being confirmed that the equilibrium favours the formation of the keto form. The bond dissociation enthalpies (N-H) and (C-H) and the gas-phase acidities were also determined. The electrostatic potential surfaces and the frontier molecular orbitals were determined for both compounds, allowing us to infer about their reactivity properties. Other properties studied include the HOMO-LUMO energy gap and the ionization potential.

Standard molar enthalpy of formation of vanillin

Specific energy of combustion of vanillin was determined using the bomb calorimeter BIC 100 with high degree of thermal protection from environment impact. The standard deviation of mean for energy equivalent was 0.01%. Based on the specific energy of combustion −(25,072.1 ± 7.4) J g−1, the standard molar enthalpy of combustion and standard molar enthalpy of formation for vanillin in the crystalline state at 298.15 K were calculated to be −(3815.9 ± 1.1) and −(475.5 ± 1.5) kJ mol−1, respectively. Standard molar enthalpy of formation of vanillin in the gaseous state was determined to be −(375.8 ± 2.1) kJ mol−1 from ab initio calculations using density functional theory and G3 methods. The enthalpy of sublimation of vanillin at 298.15 K, determined as difference between standard molar enthalpies of formation of vanillin in crystalline and gaseous states, was found to be 100 ± 3 kJ mol−1.

Tuning the structural, electronic and electrochemical properties of the 4-methyl-1-phenyl triazolium based [PhMeTAZ][Y1–8] ionic liquids through changing anions: A quantum chemical study

The many ionic liquids properties can be tuned for specific applications by changing their constituent ions. In the present work, the effect of anion variations on the structural, electronic and thermodynamic characteristics of the tunable phenyl methyl triazolium based ionic liquids [PhMeTAZ][Y1–8] (Y=CH3COO−, NO3−, CF3COO−, BF4−, ClO4−, N(CN)2−, Tf2N− and C(CN)3− were explored at M06–2X/6-311++G(d,p) level of theory. Thermodynamic binding energy of ion pairs were assessed using M06-2X and dispersion corrected M06-2X-D3, B2PLYP-D and mPW2PLYP-D functionals. Based on the Grimme's dispersion corrected binding ΔG values, strength of the inter-ionic interactions in the ILs decreases in the following order: [PhMeTAZ][CH3COO]>[PhMeTAZ][CF3COO]>[PhMeTAZ][NO3]>[PhMeTAZ][BF4]>[PhMeTAZ][ClO4]>[PhMeTAZ][N(CN)2]>[PhMeTAZ] [Tf2N]>[PhMeTAZ] [C(CN)3]. In addition, thermodynamic functions of formation and combustion of ionic liquids (ΔHf°,298, ΔGf°,298 and ΔH°c,298 using CBS-QB3 composite method), electrochemical stability of the cations and anions, electrochemical window (ECW), crystal lattice energy and volumetric based properties were assessed. The ΔHf°,298 and ΔGf°,298 of all ILs are positive and those of Y3, Y5 and Y6 based ILs are greater than others, indicating that formation of these ionic liquids is high energetic. The molar enthalpy of combustion for Y1, Y4 and Y6 based ILs is greater than 1500.0kcalmol−1. Our results also show that ECW of [PhMeTAZ][BF4] and [PhMeTAZ][Tf2N] ILs are set only by aromatic [PeMeTAZ]+ cation, in contrast to those found for other ILs.

Studies on 3,3′-diamino-4,4′-azofurazan (DAAF)

The specific heat capacity of 3,3′-diamino-4,4′-azofurazan (DAAF) was determined by a differential scanning calorimetry. In the temperature range of 253–373 K, the specific heat capacity (C p) versus T relationship can be fitted into a linear equation: C p (J g−1 K−1) = 0.0028T + 0.26456. The standard molar heat capacity is 215.53 J mol−1 K−1 at 298.15 K. According to the relationship between the specific heat capacity and thermodynamic functions, enthalpy, entropy, Gibbs free energy increments [H T–H 298.15], [S T–S 298.15] and [G T–G 298.15] of DAAF from 253 to 373 K with temperature interval of 10 K, relative to the standard temperature 298.15 K were calculated. The combustion energy of DAAF was measured by a precise IKA C5000 oxygen-bomb calorimeter to be Δc U = −(13188.43 ± 32.77) J g−1. The standard molar enthalpy of combustion at 298.15 K was determined to be Δc H m = −(2575.68 ± 6.42) kJ mol−1. The standard molar enthalpy of formation was calculated to be Δf H m = 429.98 ± 6.44 kJ mol−1 in accordance with Hess’s law. The detonation velocity and detonation pressure were calculated as 7.31 km s−1 and 23.61 GPa using the Kamlet–Jacobs equations according to the experimental enthalpy of formation.

Comprehensive thermodynamic study of methylprednisolone

In the present work the temperature dependence of heat capacity for methylprednisolone has been measured for the first time over the temperature range from 6 to 350K using by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the methylprednisolone, namely, the heat capacity, enthalpy H°(T)−H°(0), entropy S°(T)−S°(0) and Gibbs function G°(T)−H°(0) have been evaluated from the experimental values for the range from T→0 to 350K. Standard molar enthalpy of combustion (−11898.9±6.7)kJ·mol−1 of the methylprednisolone was measured for the first time using high-precision combustion calorimeter. The standard molar enthalpy of formation in the crystalline state (−1045.8±7.3)kJ·mol−1 of compound at 298.15K was derived from the combustion experiments. The standard molar enthalpy of sublimation at 298.15K (194.5±2.2)kJ·mol−1 was measured by using the quartz-crystal microbalance (QCM). Using combination of the adiabatic and combustion calorimetry with the result from QCM, the thermodynamic functions of the methylprednisolone at T=298.15K and p=0.1MPa have been calculated.

Thermodynamic properties of 3D copper(II)-MOFs assembled by 1H-tetrazole

Three-dimensional MOFs, {[Cu3(tz)4Cl2] 2CH3OH}n (Htz = 1H-1,2,3,4-tetrazole), have been synthesized in methanol. It was characterized by chemical analysis, element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. Thermogravimetric analysis demonstrated that the MOFs after removing methanol molecules possessed good thermostability with decomposition temperature up to 533 K. The enthalpy change of liquid-phase formation reaction was determined by a RD496–2000 microcalorimeter at 298.15 K with the value of (−46.63 ± 0.26) kJ mol−1. The enthalpy change of solid-phase formation reaction was calculated as (−573.89 ± 0.89) kJ mol−1 on the basis of a designed thermochemical cycle. The thermodynamics of formation reaction of the MOFs was investigated by changing the temperature of liquid-phase reaction. Based on the experimental results, fundamental kinetic and thermodynamic parameters k, n, E, $$\Delta H_{ \ne }^{\theta }$$ , $$\Delta S_{ \ne }^{\theta }$$ and $$\Delta G_{ \ne }^{\theta }$$ were obtained. The specific heat capacity at 298.15 K was determined to be (1.87 ± 0.08) J K−1 g−1 by a RD496-2000 calorimeter. In addition, the constant volume combustion energy of title MOFs was determined by a RBC-II rotating-bomb calorimeter at 298.15 K. The standard molar enthalpy of combustion and standard molar enthalpy of formation were calculated to be (−4736.43 ± 4.03) kJ mol−1 and (293.42 ± 4.11) kJ mol−1, respectively.

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.