Thermochemical properties of three piperidine derivatives

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.     

Thermochemical studies of 1-hydroxyisoquinoline, 5-hydroxyisoquinoline and 1,5-dihydroxyisoquinoline

The standard (p^° = 0.1 MPa) molar enthalpies of formation, , for crystalline 1-hydroxyisoquinoline, 5-hydroxyisoquinoline and 1,5-diidroxyisoquinoline, were derived from the standard molar enthalpies of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry. The standard molar enthalpies of sublimation, , at T = 298.15 K, were determined by Calvet microcalorimetry. The results were as follows:

1-Hydroxyisoquinoline	4395.1 ± 1.5	113.6 ± 2.2
5-Hydroxyisoquinoline	4455.2 ± 1.9	109.6 ± 2.1
1,5-Dihydroxyisoquinoline	4194.1 ± 2.2	123.6 ± 2.2

Full-size table

     

Thermochemical Study of the Cyanophenol Isomers

The standard (p° = 0.1MPa) molar enthalpies of formation for 2-, 3- and 4-cyanophenol in the gaseous phase were derived from the standard molar enthalpies of combustion in oxygen at T = 298.15 K, measured by static bomb combustion calorimetry, and the standard molar enthalpies of sublimation at 298.15 K, measured by Calvet microcalorimetry: 2-cyanophenol, (32.8 ± 2.1) kJ-mol^–1; 3-cyanophenol, (37.8 ± 2.2) kJ-mol^–1; 4-cyanophenol, (35.1 ± 2.5)-kJ-mol^–1. Ab initio geometry optimizations of the three cyanophenols and respective phenoxyl radicals and phenoxide anions were performed using the 6-31G* basis sets. Single-point MP2 and DFT energy calculations allowed the estimation of the enthalpies of formation in the gaseous phase, the O—H bond dissociation energies, and the gas-phase acidities of the three cyanophenols. The theoretical results are generally in good agreement with the experimental findings.     

Thermochemical studies on the thioproline

The combustion energy of thioproline was determined by the precision rotating-bomb calorimeter at 298.15 K to be Δ_c U= –2469.30±1.44 kJ mol^–1. From the results and other auxiliary quantities, the standard molar enthalpy of combustion and the standard molar enthalpy of formation of thioproline were calculated to be Δ_c H _m ^θC₄H₇NO₂S, (s), 298.15 K= –2469.92±1.44 kJ mol^–1 and Δ_f H _m ^θC₄H₇NO₂S, (s), 298.15K= –401.33±1.54 kJ mol^–1.     

一水合邻菲罗啉的热化学性质

用纯度为99.999%的量热基准苯甲酸标定了实验室建立的精密转动弹量热计,其能当量为18604.99±8.14J/K,测得一水合邻菲罗啉(phen·H2O)的燃烧能为-5757.45±2.53kJ/mol,换算成标准燃烧焓为-5759.93±2.53kJ/mol,进而计算出一水合邻菲罗啉的标准生成焓为-391.34±2.98kJ/mol。     

Thermochemical study of some cubane derivatives

The thermochemical study of cubane-1,4-dicarboxylic acid (1), diethyl cubane-1,4-dicarboxylate (2), diisopropyl cubane-1,4-dicarboxylate (3), and bis(2-fluoro-2,2-dinitro)ethyl cubane-1,4-dicarboxylate (4) was performed. The standard enthalpies of combustion (_c H°) and formation (_f H°) of these compounds were estimated using the method of combustion in a calorimetric bomb in an oxygen atmosphere. Using the additive group method, calculated values for _f H° of these substances which agreed satisfactorily with the experimental ones were obtained. The strain energies (E _s) of the cubic structure of derivatives1–4 were calculated. It was concluded thatE _s did not change on substitution of hydrogen atoms in cubane for various functional groups and was equal toE _s of the structure of cubane itself. The reliability of the single published value of _f H° in the cubane crystal state, 541.8 kJ mol^–1 (129.5 kcal mol^–1), was confirmed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2471–2473, October, 1996.     

Thermochemical study of aliphatic and phenyl-substituted geminal diacetates

The standard enthalpies of combustion _c H ^o of aliphatic diacetates1 and aromatic diacetates2 were measured calorimetrically. The enthalpies of vaporization _vap H ^o or sublimation _sub H ^o of1 and2 were obtained from the temperature function of the vapor pressure measured in a flow system. From _f H ^o(g) of1 and2 new values of group increments for the estimation of standard enthalpies of formation of these classes of compounds were derived. The geminal interaction energy between the geminal acyloxy groups shows no anomeric stabilization.Geminal Substituent Effects, Part 12, for part 11 see Ref. 7.     

Thermochemical Properties and Non-isothermal Decomposition Reaction Kinetics of N-Guanylurea Dinitramide （GUDN）

Introduction N-Guanylurea dinitramide (GUDN) is a new ener-getic oxidizer with higher energy and lower sensitivity. Its crystal density is 1.755 g·cm-3. The detonation velocity is about 8210 m·s-1. Its specific impulse and pressure exponent are 213.1 s and 0.73, respectively. It has the potential for possible use as an energy ingredient of propellants and explosives from the point of view of the above-mentioned high performance. Its preparation,1 properties2 and hygroscopocity2 have been …     

Thermochemical study of 2- and 3-alkyl substituted thiophenes

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.     

Thermochemical study of 1-, 3- and 4-piperidinecarboxamide derivatives

The standard (p° = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, in the gaseous phase, of three piperidinecarboxamide derivatives, namely 1-, 3- and 4-piperidinecarboxamide, were determined from their enthalpies of combustion and sublimation, obtained by static bomb calorimetry in oxygen and by Calvet microcalorimenty, respectively.The final results are analysed and discussed in terms of molecular structure.     

Thermochemistry of Alcohols: Experimental Standard Molar Enthalpies of Formation and Strain of Some Alkyl and Phenyl Congested Alcohols

The standard molar enthalpies of formation _f H _m ^° (cr) at the temperature T = 298.15 K were determined using combustion calorimetry for di-tert-butyl-methanol (A), di-tert-butyl-iso-propyl-methanol (B), and di-phenyl-methyl-methanol (C). The standard molar enthalpies of sublimation _cr ⁸ H _m ^° of these compounds and of di-phenyl-methanol (D) were obtained from the temperature variation of the vapor pressure measured in a flow system. Molar enthalpies of fusion _cr ¹ H _m ^° of the compounds A–D and of tri-phenyl-methanol (E) were measured by differential scanning calorimeter (DSC). From these data and data available from the literature, the following standard molar enthalpies of formation in gaseous phase _f H _m ^° (g) for A, (–397.0 ± 1.2); B, (–418.1 ± 2.3); C, (–34.2 ± 1.3); and D, (0.9 ± 2.1) kJ · mol^–1 were derived, which correspond to strain enthalpies (H _S) of 46.1, 114.7, 8.1, and 5.0 kJ · mol^–1, respectively.     

Thermochemical studies for determination of the molar enthalpy of formation of aniline derivatives

The standard (p ^o=0.1 MPa) molar enthalpies of combustion atT=298.15 K were measured by static bomb combustion calorimetry for liquidN,N-diethylaniline,N,N-dimethyl-m-toluidine,N,N-dimethyl-p-toluidine, andN-ethyl-m-toluidine. Vaporization enthalpies forN,N-dimethyl-m-toluidine andN-ethyl-m-toluidine were determined by correlation gas chromatography. Derived standard molar values of _f H _m ^o (g) at 298.15 K forN,N-diethylaniline (62.1±7.6);N,N-dimethyl-m-toluidine (72.6±7.3),N,N-dimentyl-p-toluidine (68.9±7.4),N-ethyl-m-toluidine (30.5±3.8 kJ· mol^–1) were obtained.     

Strain Energies of α-Alkylsubstituted Styrenes, 1,1-Di-phenyl-ethene,Tri-, and Tetra-phenyl-ethene

The standard (p° = 0.1 MPa) molar enthalpies of formation _fH°_m (1 or cr) at the temperature T = 298.15 K were determined by using combustion calorimetry for -ethyl-styrene (A), -iso-propyl-styrene (B), -tert-butyl-styrene (C), 1,1-di-phenyl-ethene (D), tri-phenyl-ethene (E), and tetra-phenyl-ethene (F). The standard molar enthalpies of vaporization _l ^g H°_m or sublimation _cr ^g H°_m of compounds A to F were obtained from the temperature variation of the vapor pressure measured in a flow system. Molar enthalpies of fusion _cr ^l H°_m of solid compounds were measured by d.s.c. Resulting values of _fH°_m (g) were obtained at the temperature T = 298.15 K and used to derive strain enthalpies of phenylalkenes. The interactions of the substituents are discussed in terms of deviations of _fH°_m (g)from the group additivity rules. These values provide a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.     

Thermochemical properties of the rare earth complexes with pyromellitic acid

Fourteen rare earth complexes with pyromellitic acid were synthesized and characterized by means of chemical and elemental analysis, and TG–DTG. The constant-volume combustion energies of complexes, Δ_cU, were measured by a precise rotating-bomb calorimeter (RBC-type II). Their standard molar enthalpies of combustion, , and standard molar enthalpies of formation, , were calculated at T = 298.15 K. The relationship of and with the atomic numbers of the elements in the lanthanide series was examined. The results show that a certain amount of covalence is present in the chemical bond between rare earth cations and the ligand.     

Thermochemical study of three dimethylpyrazine derivatives

The standard (p ⁰=0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T-298.15 K, for 2,5-dimethylpyrazine (2,5-DMePz) and for the two dimethylpyrazine-N,N′-dioxide derivatives, 2,3-dimethylpyrazine-1,4-dioxide (2,3-DMePzDO) and 2,5-dimethylpyrazine-1,4-dioxide (2,5-DMePzDO), were derived from the measurements of standard massic energies of combustion, using a static bomb calorimeter, and from the standard molar enthalpies of vaporization or sublimation, measured by Calvet microcalorimetry. The mean values for the molar dissociation enthalpy of the nitrogen-oxygen bonds, 〈DH _m⁰〉(N-O), were derived for both N,N′-dioxide compounds. These values are discussed in terms of the molecular structure of the two N,N′-dioxide derivatives and compared with 〈DH _m⁰〉(N-O) values previously obtained for other N-oxide derivatives.     

Thermochemical Studies for Determination of the Standard Molar Enthalpies of Formation of Alkyl-Substituted Furans and Some Ethers

The standard molar enthalpies of vaporization _l ^g H _m ^º of 2,5-dimethylfuran, 2-tert-butylfuran, 2,5-di-tert-butylfuran, cyclopentenyl methyl ether, cyclohexenyl methyl ether, and tert-amyl methyl ether were obtained from the temperature variation of the vapor pressure measured in a flow system. The standard (p° = 0.1 MPa) molar enthalpies of formation _f H _m ^º (1) at the temperature T = 298.15 K were measured using combustion calorimetry for 2,5-dimethylfuran, 2-tert-butylfuran, and 2,5-di-tert-butylfuran. From the derived standard molar enthalpies of formation for gaseous compounds, ring correction terms and non-nearest neighbor interactions useful in the application of the Benson group additivity scheme were calculated.     

Thermochemical study of the isomeric compounds: 3-acetylbenzonitrile and benzoylacetonitrile

The standard (p° = 0.1 MPa) molar enthalpies of formation of 3-acetylbenzonitrile and benzoylacetonitrile, in the crystalline phase, were derived from the respective standard massic energies of combustion measured by static bomb combustion calorimetry, in oxygen, at T = 298.15 K. The standard molar enthalpies of sublimation, at T = 298.15 K, were measured by Calvet microcalorimetry. From the above experimentally determined enthalpic parameters, the standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, are found to be: (52.4 ± 2.1) kJ · mol⁻¹ and (74.8 ± 2.5) kJ · mol⁻¹ for 3-acetylbenzonitrile and benzoylacetonitrile, respectively.Molecular structures were computed using highly accurate ab initio techniques. Standard molar enthalpies of formation of the experimentally studied compounds were derived using an appropriate set of working reactions. Very good agreement between the calculated and the experimental values was obtained, so the calculations were extended to the estimates of the standard molar enthalpies of formation of 2- and 4-acetylbenzonitriles whose study was not performed experimentally.Our results were further interpreted and rationalized in terms of the enthalpic stability and compared to other relevant disubstituted benzenes.     

氯化镧与甘氨酸配位反应的热化学研究

The reaction enthalpy of coordination reaction of lanthanum chloride with Glycine is determined by solution calorimetry in an isoperibel reaction calorimeter. The calormetric solvent is the solution of hydrochloric acid (2 mol·L- 1), a new thermochemical cycle is designed. According to the results, the following date:()(298.2 K)=- 4.310 kJ·mol- 1()(La(Gly)3Cl3· 5H2O, s, 298.2 K)=- 4222.93 kJ·mol- 1 were obtained.     

Standard Enthalpies of Formation for Some Semi-products At the Synthesis of Poly(ethylene) Terephthalate

The enthalpies of combustion for 4-formylbenzoic acid (I), 4-methylbenzyl alcohol (II), and trimethyl 1,2,4-benzenetricarboxylate (III) were determined by the bomb calorimetry method. Enthalpies of sublimation for I and II were measured with a calorimeter. The contributions of different substituents to the standard enthalpies of formation for benzene derivatives in the gas state were derived. This revised version was published online in July 2006 with corrections to the Cover Date.     

硝酸镝与丙氨酸配位反应的热化学研究

采用新型的具有恒温环境的反应热量计 ,以 2mol L的HCl作溶剂 ,分别测定了 [Dy(NO3) 3·6H2 O +4Ala]和Dy(Ala) 4(NO3) 3·H2 O在 2 5℃时的溶解焓。通过设计的热化学循环得到六水硝酸镝与丙氨酸配位反应的反应焓ΔrHmθ=30 .638kJ mol,并计算出配合物Dy(Ala) 4(NO3) 3·H2 O在 2 98.1 5K时的标准生成焓ΔfHmθ=-3833.8kJ mo