Saturated vapor pressures and the enthalpies of vaporization of dicyclohexyl esters of dicarboxylic acids

Saturated vapor pressures at 320–370 K and the enthalpies of vaporization of dicyclohexyl esters of linear dicarboxylic acids containing two to six carbon atoms were determined by the transpiration method. Linear correlations of the enthalpies of vaporization of the esters with the number of carbon atoms in molecules and Kováts retention indices were obtained.     

Saturation vapor pressures and vaporization enthalpies of esters of ethylene glycol and lower carboxylic acids

Saturation vapor pressures and vaporization enthalpies of ethylene glycol and C₁–C₅ carboxylic acid disubstituted esters of normal and branched structures are determined by the transfer method in the temperature range of 295 to 327 K. Dependences of vaporization enthalpies versus the number of carbon atoms in a molecule and the retention indices are determined. An analysis of existing calculation schemes is given to help predict the vaporization enthalpy of the compounds under study.     

Determination of vapor pressures and enthalpies of vaporization of 1,2-alkanediols

Molar enthalpies of vaporization of 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The measured data sets were successfully checked for internal consistency. A large number of the primary experimental results on temperature dependences of vapor pressures have been collected from the literature and have been treated uniform in order to derive vaporization enthalpies at the reference temperature 298.15 K. This collection together with the experimental results reported here has helped to resolve some contradictions which have been met in the available literature.     

Experimental vapor pressures of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides and a correlation scheme for estimation of vaporization enthalpies of ionic liquids

Vapor pressures for a series of 1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (alkyl = ethyl, butyl, hexyl, and octyl) ionic liquids (ILs) were measured by the integral effusion Knudsen method. Thermodynamic parameters of vaporization for ILs were calculated from these data. The absence of decomposition of ILs during the vaporization process was proved by IR spectroscopy. Enthalpies of vaporization of ILs were correlated with molar volumes and surface tensions of the compounds.     

The vaporization enthalpies and vapor pressures of a series of unsaturated fatty acid methyl esters by correlation gas chromatography

Vaporization enthalpies for methyl myristoleate (methyl Z 9-tetradecenonate), methyl 10-pentadecenoate, methyl palmitoleate (methyl Z 9-hexadecenoate), methyl Z 10-heptadecenoate, methyl oleate (methyl Z 9-octadecenoate), methyl linoleate (methyl Z,Z 9,12-octadecadienoate), methyl linolenate (methyl Z,Z,Z 9,12,15-octadecatrienoate), methyl Z 11-eicosenoate, methyl Z,Z 11,14-eicosadienoate, methyl Z,Z,Z 11,14,17-eicosatrieneoate, methyl arachidonate (methyl Z,Z,Z,Z 5,8,11,14-eicosatetraeneoate), methyl Z,Z,Z,Z,Z 5,8,11,14,17-eicosapentaeneoate, methyl erucate (methyl Z 13-docosaneoate), methyl Z,Z 13,16-docosadienoate, methyl Z,Z,Z,Z,Z,Z 4,7,10,13,16,19-docosahexaenoate and methyl nervonate (methyl Z 15-tetracosenoate) are evaluated at T = 298.15 and vapor pressures are evaluated over the temperature range T = 298.15-450 K by correlation gas chromatography. The results are generated by an interpolative process using literature values for the saturated fatty acid methyl esters (FAMEs) from methyl decanoate to methyl tetracosanoate, exclusive of methyl nonadecanoate, heneicosanoate and tricosanoate, as standards. Relationships for calculating vapor pressures for all of the compounds studied from T = 298.15 to 450 K are provided.     

Prediction of vapor pressures and enthalpies of vaporization of organic compounds from the normal boiling point temperature

Recently, our Laboratory proposed a model for the prediction of vapor pressures of organic compounds that requires only the knowledge of the normal boiling point of the compound involved, and a compound specific K_f for which generalized expressions for several classes of organic compounds as functions of the normal boiling point and the molecular weight were developed.In this work our model is compared with the one proposed in Lyman's book, which is similar to our model but uses different K_f values. The results indicate that our model provides very satisfactory results in the temperature range from the melting up to the normal boiling point and up to the critical, where no hydrogen-bonding is involved. Also, it is proven that the accuracy of our model is much better than that proposed by Lyman, especially for the high molecular weight compounds.Finally, our model is used for the prediction of enthalpies of vaporization at the normal boiling point. Excellent results are obtained that are comparable or better than those obtained with two recommended models in “The Properties of Gases and Liquids” book, where the latter, however, require as input information except from the normal boiling point the critical properties of the compound involved as well.     

A new approach for the estimation of sublimation enthalpies and vapor pressures of crystalline benzene derivatives

This work presents a new approach for estimating sublimation enthalpies and vapor pressures of substituted benzenes. Proposed estimating equations were based on a collection of selected literature results of vapor pressures of ca. 240 benzene derivatives attached with 30 different substituents. Compared to experimental results, best estimates are obtained from the equations that include the temperature of fusion. A review of the results determined for substituted benzenes using two different calorimetric techniques shows that the results of enthalpies of sublimation derived from vapor pressures seem to be more reliable than those derived from the calorimetric techniques.     

Saturated vapor pressures and enthalpies of evaporation of esters of glycerol and lower carboxylic acids

Saturated vapor pressures and enthalpies of evaporation of trisubstituted esters of glycerol and carboxylic acids C₁–C₅ with normal and branched structure were determined by the transpiration method in the temperature range of 300–371 K. Dependences of enthalpies of evaporation on the number of carbon atoms in a molecule and on the retention indices are established. Prognostic possibilities of existing calculation schemes are analyzed for compounds with three carboxyl groups in a molecule.     

An examination of the vaporization enthalpies and vapor pressures of pyrazine, pyrimidine, pyridazine, and 1,3,5-triazine

The vaporization enthalpies and liquid vapor pressures from T = 298.15 K to T = 400 K of 1,3,5-triazine, pyrazine, pyrimidine, and pyridazine using pyridines and pyrazines as standards have been measured by correlation-gas chromatography. The vaporization enthalpies of 1,3,5-triazine (38.8 ± 1.9 kJ mol⁻¹) and pyrazine (40.5 ± 1.7 kJ mol⁻¹) obtained by these correlations are in good agreement with current literature values. The value obtained for pyrimidine (41.0 ± 1.9 kJ mol⁻¹) can be compared with a literature value of 50.0 kJ mol⁻¹. Combined with the condensed phase enthalpy of formation in the literature, this results in a gas-phase enthalpy of formation, Δ_f H _m (g, 298.15 K), of 187.6 ± 2.2 kJ mol⁻¹ for pyrimidine, compared to a value of 195.1 ± 2.1 calculated for pyrazine. Vapor pressures also obtained by correlation are used to predict boiling temperatures (BT). Good agreement with experimental BT (±4.2 K) including results for pyrimidine is observed for most compounds with the exception of the pyridazines. The results suggest that compounds containing one or two nitrogen atoms in the ring are suitable standards for correlating various heterocyclic compounds provided the nitrogen atoms are isolated from each other by carbon. Pyridazines do not appear to be evaluated correctly using pyridines and pyrazines as standards.     

Thermogravimetric method used to determine the saturated vapor pressure in a wide range of values

Thermogravimetric method was used to study the evaporation of a number of solvents. The evaporation coefficients in the Langmuir equation were calculated in relation to the conditions of a thermogravimetric experiment (atmospheric pressure, carrier-gas) and nature of a substance under study.     

Vapour pressures and enthalpies of vaporization of a series of substituted phenyl isobutyl ethers

Molar enthalpies of vaporization of 2-Br-phenyl isobutyl ether, 3-Br-phenyl isobutyl ether, 4-Br-phenyl isobutyl ether, and 2-Br-4-Me-phenyl isobutyl ether were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The measured data sets were successfully checked for internal consistency. The values of enthalpies of vaporization and vapor pressures of ortho-, meta-, and para-substituted benzenes are discussed in the context.     

Vapor pressures and enthalpies of vaporization of a series of 1- and 2-halogenated naphthalenes

Molar enthalpies of vaporization, Δ_l^gH_m⁰, of 1-methyl-naphthalene, 1-chloro-napthalene, 2-chloro-naphthalene, 1-bromo-naphthalene, 2-bromo-naphthalene, and 1-iodo-naphthalene, as well as molar enthalpies of sublimation, Δ_s^gH_m⁰, of 2-chloro-naphthalene and 2-bromo-naphthalene have been obtained from the temperature dependence of the vapor pressure determined with the transpiration method. These values and the correlation gas-chromatography method, based on the Kovat’s index, have been used to determine Δ_l^gH_m⁰ and Δ_s^gH_m⁰ of 2-iodo-naphthalene. Results obtained in this work have been compared with those from the literature and found consistent.     

Thermochemical properties of benzoic acid derivatives XI. Vapour pressures and enthalpies of sublimation and formation of the six dimethylbenzoic acids

The energies of combustion of 3,4- and 3,5-dimethylbenzoic acids have been revised by combustion calorimetry. Vapour pressures of very pure samples of the six dimethylbenzoic acids have been determined over a range of temperatures near 298 K by the Knudsen-effusion technique. From the experimental results and our previously published thermochemical quantities the following results for the six C₆H₃(CH₃)₂CO₂H isomers at 298.15 K have been derived.

     

18.

Vapour pressures,enthalpies and entropies of sublimation of <Emphasis Type="Italic">para</Emphasis> substituted benzoic acids     

Manuel J. S. Monte  Luís M. N. B. F. Santos  José M. S. Fonseca  Carlos A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2010,100(2):465-474

The vapour pressures of six para-substituted benzoic acids were measured using the Knudsen effusion method within the pressure range (0.1–1 Pa) in the following temperature intervals: 4-hydroxybenzoic acid (365.09–387.28) K; 4-cyanobenzoic acid (355.14–373.28) K; 4-(methylamino)benzoic acid (359.12–381.29) K; 4-(dimethylamino)benzoic acid (369.29–391.01) K; 4-(acetylamino)benzoic acid (423.10–443.12) K; 4-acetoxybenzoic acid (351.28–373.27) K. From the temperature dependence of the vapour pressure, the standard molar enthalpy, entropy and Gibbs energy of sublimation, at the temperature 298.15 K, were derived for each of the studied compounds using estimated values of the heat capacity differences between the gaseous and the crystalline phases. Equations for estimating the vapour pressure of para substituted benzoic acids at the temperature of 298.15 K are proposed.     

19.

Thermogravimetry as a screening tool for the estimation of the vapor pressures of pure compounds     

Federica Barontini  V. Cozzani 《Journal of Thermal Analysis and Calorimetry》2007,89(1):309-314

A simplified approach was developed to estimate the vapor pressure of pure compounds from experimental data obtained by isothermal thermogravimetric (TG) analysis. A numerical procedure was developed to estimate the Antoine parameters of the substance by the analysis of isothermal TG data. The results of the experimental validations carried out evidenced that at least a preliminary estimation of vapour pressures of pure substances by the analysis of TG data is possible. The limited time and the reduced amounts of sample required for the experimental runs make the technique attractive with respect to the conventional and more accurate techniques for vapor pressure assessment.     

20.

Isotactic polypropylene: An attempt to correlate crystallization conditions,superreticular structure,and impact properties     

Roberto Greco  Pellegrino Musto  Giuseppe Ragosta  Fernando Riva 《Macromolecular rapid communications》1988,9(2):91-95

     

Isomer		$\text{Δ}{}_{\mathrm{<mtext>f</mtext>}}\text{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(cr)}$	$\text{Δ}{}_{\mathrm{<mtext>sub</mtext>}}\text{H}{}_{\mathrm{m}}{}^{\mathrm{o}}$	$\text{Δ}{}_{\mathrm{<mtext>f</mtext>}}\text{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(g)}$
	kJ·mol?1	kJ·mol?1	kJ·mol?1
2,6-	?440.7 ± 1.7	99.1 ± 0.2	?341.6 ± 1.7
2,3-	?450.4 ± 1.7	104.6 ± 0.4	?345.8 ± 1.7
2,5-	?456.1 ± 1.6	105.0 ± 0.6	?351.1 ± 1.7
2,4-	?458.5 ± 1.7	103.5 ± 0.3	?355.0 ± 1.7
3,4-	?468.8 ± 1.9	106.4 ± 0.3	?362.4 ± 1.9
3,5-	?466.8 ± 1.7	102.3 ± 0.3	?364.5 ± 1.7

Vapour pressures,enthalpies and entropies of sublimation of <Emphasis Type="Italic">para</Emphasis> substituted benzoic acids

The vapour pressures of six para-substituted benzoic acids were measured using the Knudsen effusion method within the pressure range (0.1–1 Pa) in the following temperature intervals: 4-hydroxybenzoic acid (365.09–387.28) K; 4-cyanobenzoic acid (355.14–373.28) K; 4-(methylamino)benzoic acid (359.12–381.29) K; 4-(dimethylamino)benzoic acid (369.29–391.01) K; 4-(acetylamino)benzoic acid (423.10–443.12) K; 4-acetoxybenzoic acid (351.28–373.27) K. From the temperature dependence of the vapour pressure, the standard molar enthalpy, entropy and Gibbs energy of sublimation, at the temperature 298.15 K, were derived for each of the studied compounds using estimated values of the heat capacity differences between the gaseous and the crystalline phases. Equations for estimating the vapour pressure of para substituted benzoic acids at the temperature of 298.15 K are proposed.     

Thermogravimetry as a screening tool for the estimation of the vapor pressures of pure compounds

A simplified approach was developed to estimate the vapor pressure of pure compounds from experimental data obtained by isothermal thermogravimetric (TG) analysis. A numerical procedure was developed to estimate the Antoine parameters of the substance by the analysis of isothermal TG data. The results of the experimental validations carried out evidenced that at least a preliminary estimation of vapour pressures of pure substances by the analysis of TG data is possible. The limited time and the reduced amounts of sample required for the experimental runs make the technique attractive with respect to the conventional and more accurate techniques for vapor pressure assessment.