摘要 :
The energies of combustion of single-walled and multi-walled carbon nanotubes were measured by using an isoperibolic micro-combustion calorimeter. The values of the massic energy of combustion in oxygen at T = 298.15 K and pAA = 0...
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The energies of combustion of single-walled and multi-walled carbon nanotubes were measured by using an isoperibolic micro-combustion calorimeter. The values of the massic energy of combustion in oxygen at T = 298.15 K and pAA = 0.1 MPa of the compounds under study were obtained as: (- 27,635.0 +/- 9.5) and (- 32,347.3 +/- 15.3) J g(-1), respectively. The corresponding standard molar enthalpies of formation were derived as: (4.7 +/- 1.3) and (0.8 +/- 0.9) kJ mol(-1), respectively. The used calorimeter to test the compounds was calibrated previously with benzoic acid NIST 39j, salicylic acid and 1,2,4-triazole.
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Carbon nanotubes (CNTs) with different content of carboxylated groups on their surface (depending on the duration of their treatment with nitric acid) were synthesized. All samples were analyzed by thermal analyses, X-ray photoele...
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Carbon nanotubes (CNTs) with different content of carboxylated groups on their surface (depending on the duration of their treatment with nitric acid) were synthesized. All samples were analyzed by thermal analyses, X-ray photoelectron spectroscopy, Raman and energy-dispersive X-ray spectroscopy, transmission electron microscopy and S-BET. The adiabatic bomb calorimetry technique was used for the determination of enthalpy of formation. With the increase in time of treatment from 3 to 9 h, the content of oxygen increased from 7.49 to 8.22 at%. After 15-h treatment in nitric acid, CNTs contained 7.86 at%. The enthalpies of formation of all samples were negative and had nonlinear character. The changes of surface and bulk physicochemical characteristics of oxidized CNTs were analyzed. It was shown that despite decrease in surface enthalpy of formation a dagger(f) H (0)(298(surf.)) with the increase in oxygen content, the bulk enthalpy of formation a dagger(f) H (0)(298(bulk)) was very sensitive to defectiveness and structure of carbon layers. It resulted in the difficult correlation between oxygen content, morphology, defectiveness and a dagger(f) H (0)(298).
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The standard (p~o=0.1 MPa) molar enthalpies of formation #DELTA#_fH_m~o(1,or cr)at T=298.15 K were determined by means of combustion calorimetry for 2-methylnitrobenzene,2-ethylnitrobenzene,2-isopropylnitrobenzene,2-tert-butylnitr...
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The standard (p~o=0.1 MPa) molar enthalpies of formation #DELTA#_fH_m~o(1,or cr)at T=298.15 K were determined by means of combustion calorimetry for 2-methylnitrobenzene,2-ethylnitrobenzene,2-isopropylnitrobenzene,2-tert-butylnitrobenzene,2,6-dimethylnitrobenzene,2,6-di-isopropyl-nitrobenzene,and 2,4,6-tri-tert-butylnitrobenzene.The molar enthalpies of sublimation (or these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system.The resulting values of #DELTA#_fH_m~o(g) were obtained at T=298.15 K and used to derive strain enthalpies of alkylnitrobenzenes.The intramolecular interactions of the substituents were discussed in terms of deyiations of #DELTA#_fH_m~o(g) from group additivity fules.These values provide a further improvement on the group-contribution methodology for the estimation of the thermodynamci properties of organic compounds.
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摘要 :
The standard (p~o = 0.1 MPa) molar enthalpies of formation #delta#H_m~o(1, or cr) at T = 298.15 K were determined by means of combustion calorimetry for 2-methylnitrobenzene, 2-ethylnitrobenzene, 2-isopropylnitrobenzene, 2-tert-bu...
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The standard (p~o = 0.1 MPa) molar enthalpies of formation #delta#H_m~o(1, or cr) at T = 298.15 K were determined by means of combustion calorimetry for 2-methylnitrobenzene, 2-ethylnitrobenzene, 2-isopropylnitrobenzene, 2-tert-butylnitrobenzene, 2,6-dimethyl-nitrobenzene, 2,6-di-isopropyl-nitrobenzene, and 2,4,6-tri-tert-butylnitrobenzene. The molar enthalpies of sublimation (or vaporization) of these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system. The resulting values of #delta#_fH_m~o(g) were obtained at T = 298.15 K and used to derive strain enthalpies of alkylnitrobenzenes. The intramolecular interactions of the substituents were discussed in terms of deviations of #delta#H-m~o(g) from group additivity rules. These values provide a further improvement on the group-contribution methodology for the estimation of the thermodynamic properties of organic compounds.
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The standard (p degrees = 0.1 MPa) molar enthalpies of formation Delta(f)H(m) degrees(cr) at the temperature T = 298.15 K were measured by using combustion calorimetry of 2-phenylphenol, 4-phenylphenol, 2,6-diphenylphenol, 2,2'-di...
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The standard (p degrees = 0.1 MPa) molar enthalpies of formation Delta(f)H(m) degrees(cr) at the temperature T = 298.15 K were measured by using combustion calorimetry of 2-phenylphenol, 4-phenylphenol, 2,6-diphenylphenol, 2,2'-dihydroxybiphenyl, and 4,4'-dihydroxybiphenyl. The standard molar enthalpies of sublimation Delta(cr)(g)H(m) degrees of the compounds were obtained from the temperature variation of the vapour pressure measured in a flow system. Molar enthalpies of fusion Delta(cr)(1)H(m) degrees of the compounds were measured by d.s.c. Values of the weak interactions (about 2kJ.mol(-1) to 4kJ.mol(-1)) of phenyl substituents with the hydroxyl group were derived from the enthalpies of formation in the gas phase. [GRAPHICS] (C) 1998 Academic Press Limited. [References: 14]
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The standard enthalpies of formation ΔH_f°(g) of mono- and gem-di(alkoxycarbonyl)-substituted cyclopropanes 1, cyclobutanes 2 and cyclopentanes 3 have been calculated from the standard enthalpies of combustion ΔH_c°, which wer...
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The standard enthalpies of formation ΔH_f°(g) of mono- and gem-di(alkoxycarbonyl)-substituted cyclopropanes 1, cyclobutanes 2 and cyclopentanes 3 have been calculated from the standard enthalpies of combustion ΔH_c°, which were measured calorimetrically, in combination with the standard enthalpies of vaporization ΔH_(vap)°. The latter were obtained for 1a-c, 2b-c and 3b-c from the temperature dependence of the vapor pressures, which were measured in a flow system. Contrary to suggestions in the literature, only weak stabilization (≤ 8 kJ · mol~(-1)) of small rings by gem-alkoxycarbonyl substituents was observed. In this context, we give a revised value for the enthalpy of combustion of methyl cyclobutanecarboxylate. It is concluded that the known high rates of ring closure to gem-dialkoxycarbonyl cyclopropanes are not attributable to a 'stabilizing effect' resulting from conjugation between the alkoxycarbgonyl substituents and the cyclopropane ring, as has been suggested in the literature. The operation of a Thorpe-Ingold- or gem-dimethyl-type effect would seem to offer a more satisfactory interpretation.
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The standard (p(o) = 0.1 MPa) molar enthalpies of formation Delta(f)H(m)(o)(1) at T = 298.15 K were determined by means of combustion calorimetry For benzylcyanide, alpha-methyl-benzylcyanide, alpha-ethyl-benzylcyanide, and alpha,...
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The standard (p(o) = 0.1 MPa) molar enthalpies of formation Delta(f)H(m)(o)(1) at T = 298.15 K were determined by means of combustion calorimetry For benzylcyanide, alpha-methyl-benzylcyanide, alpha-ethyl-benzylcyanide, and alpha,alpha-dimethyl-benzylcyanide. The standard molar enthalpies of vaporization of these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system. Resulting values of Delta(f)H(m)(o)(g) were obtained at T = 298.15 K and used to derive strain enthalpies of benzylcyanides. The strain effects were discussed in terms of deviations of Delta(f)H(m)(o)(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. (C) 2000 Academic Press. [References: 23]
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Thermochemical studies of some organic compounds have been done in the present communication. The enthalpy of combustion values, ΔH_c, of the compounds have been determined experimentally by measuring temperature rise per gram of...
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Thermochemical studies of some organic compounds have been done in the present communication. The enthalpy of combustion values, ΔH_c, of the compounds have been determined experimentally by measuring temperature rise per gram of the sample and obtaining the time-temperature plot by the application of Matlab. These data have been used in the calculation of standard enthalpies of formation of the compounds, ΔH_f~0.
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The compounds (4R, 5R)-3,4-dimethyl-5-phenyl-1,3-oxazolidine (OXA1), (4S,5R)-3,4dimethyl-5-phenyl-1,3-oxazolidine (OXA2) [Chemical Abstracts registry number 123618-06-4], and (4R,5R)-2,2,3,4-tetramethyl-5-phenyl-oxazolidine (OXA3)...
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The compounds (4R, 5R)-3,4-dimethyl-5-phenyl-1,3-oxazolidine (OXA1), (4S,5R)-3,4dimethyl-5-phenyl-1,3-oxazolidine (OXA2) [Chemical Abstracts registry number 123618-06-4], and (4R,5R)-2,2,3,4-tetramethyl-5-phenyl-oxazolidine (OXA3) [Chemical Abstracts registry number 141271-51-4] have been studied by oxygen bomb combustion calorimetry, and the vapor pressures were measured at different temperatures by a static method. On the basis of the experimental results, the standard molar enthalpies of formation of the liquid and gaseous compounds were determined. A summary of experimental and derived results at the temperature T = 298.15 K is shown below; where Delta(c)U(m)degrees(l), Delta(c)H(m)degrees(l), Delta(f)H(m)degrees(l), Delta(l)(g)H(m)degrees(l), and Delta(f)H(m)degrees(g) denote the standard molar energy of combustion, the standard molar enthalpy of combustion, the standard molar enthalpy of formation of the liquid compound, the standard molar enthalpy of vaporization, and the standard molar enthalpy of formation of the gaseous compound, respectively. [GRAPHICS] The standard molar enthalpy of formation in the gaseous phase is decreased by 7.8 kJ . mol(-1) from compound OXA2 to OXA1. This quantity is attributed to the different configuration of the methyl group at the C-4 position of these compounds. In the envelope conformation, OXA2 has a nearly gauche interaction between the phenyl and methyl substituents, while OXA1 has a nearly anti-interaction between the same substituents. In addition, with the experimental results for compounds OXA1 and OXA3, the group contribution terms to the standard molar enthalpies of formation of the gaseous compounds for the molecular groups {C-(O)(N)(H)(2)} and {C-(O)(N)(C)(2)} were derived as -104.5 kJ . mol(-1) and -118.8 kJ . mol(-1), respectively. (C) 1998 Academic Press. [References: 14]
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The standard (p degrees = 0.1 MPa) molar enthalpies of formation Delta(f)H(m) degrees (I or cr) al the temperature T = 298.15 K were measured using combustion calorimetry for N,N-dimethyloctylamine (A), 2,4-dimethylaniline (B), 2,...
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The standard (p degrees = 0.1 MPa) molar enthalpies of formation Delta(f)H(m) degrees (I or cr) al the temperature T = 298.15 K were measured using combustion calorimetry for N,N-dimethyloctylamine (A), 2,4-dimethylaniline (B), 2,5-dimethylaniline (C), N-ethylaniline (D), N-benzylaniline (E), and N,N-dimethylaniline (F). The standard molar enthalpies of vaporization Delta(l)(g)H(m) degrees or sublimation Delta(cr)(g)H(m) degrees of the compounds were obtained from the temperature variation of the vapour pressure measured in a flow system. In order to accomplish the thermochemical investigation of tert-butyl-methylamine (G), tert-butyl-isopropylamine (H), and 2,2,6,6-tetramethylpiperidine (I), their molar enthalpies of the vaporization were measured by the transpiration method. The following results were obtained: [GRAPHICS] (C) 1997 Academic Press Limited. [References: 20]
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