Group-contribution Methodology Research Articles

Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for 1,4-Diisopropylbenzene, 1,2,4,5-Tetraisopropylbenzene, Cyclohexanone Oxime, Dimethyl Malonate, Glutaric Acid, and Pimelic Acid

The results of a study aimed at improvement of group-contribution methodology for estimation of enthalpies of formation in the ideal-gas state for pure organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurements. Enthalpies of formation in the condensed phase were determined for 1,4-diisopropylbenzene, 1,2,4,5-tetraisopropylbenzene, dimethyl malonate, glutaric acid, pimelic acid, and cyclohexanone oxime. Ideal-gas enthalpies of formation for each of the compounds except pimelic acid are also reported. Enthalpies of fusion and for crystalline phase transitions were determined for 1,2,4,5-tetraisopropylbenzene, cyclohexanone oxime, glutaric acid, and pimelic acid. Two-phase (solid + vapor) or (liquid + vapor) heat capacit...

Thermochemistry of substituted benzenes: quantification of ortho-, para-, meta-, and buttress interactions in alkyl-substituted nitrobenzenes

The standard (po= 0.1 MPa) molar enthalpies of formation ΔfHmo(l, 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 ofΔfHmo (g) were obtained atT= 298.15 K and used to derive strain enthalpies of alkylnitrobenzenes. The intramolecular interactions of the substituents were discussed in terms of deviations ofΔfHmo (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.

Thermochemical study of the ortho interactions in alkyl substituted anilines

The standard (po= 0.1 MPa) molar enthalpies of formation ΔfHmo(l or cr) at the temperature T= 298.15 K were determined by means of combustion calorimetry for 2-ethyl-aniline, 2-iso-propyl-aniline, 2-tert-butyl-aniline, 2,6-di-methyl-aniline, 2,6-di-ethyl-aniline, 2,6-di-iso-propyl-aniline, and 2,4,6-tri-tert-butyl-aniline. The standard molar enthalpies of vaporization (or sublimation) of these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system. The resulting values of ΔfHmo(g) were obtained at the temperature T= 298.15 K and used to derive strain enthalpies of alkyl-anilines. The intra-molecular interactions of the substituents were discussed in terms of deviations ofΔfHmo (g) from group additivity rules. These values provide a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.

Strain effects in phenyl substituted methanes. Geminal interactions between phenyl and electron-withdrawing cyano substituent in benzylcyanides

The standard (po= 0.1 MPa) molar enthalpies of formation ΔfHmo(l) atT= 298.15 K were determined by means of combustion calorimetry for benzylcyanide, α -methyl-benzylcyanide, α -ethyl-benzylcyanide, and α, α - 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 ofΔfHmo (g) were obtained atT= 298.15 K and used to derive strain enthalpies of benzylcyanides. The strain effects were discussed in terms of deviations ofΔfHmo (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.

Thermochemistry of phenols: buttress effects in sterically hindered phenols

The standard (po= 0.1 MPa) molar enthalpies of formation ΔfHmo(l, or cr) at the temperature 298.15 K were measured by means of combustion calorimetry for 2,3,6-tri-methylphenol, 2,4,6-tri-methylphenol, 2,6-di-iso-propylphenol, 2-tert-butyl-6-methylphenol, 2-tert-butyl-4,6-di-methylphenol, 2,6-di-tert-butylphenol, 2,6-di-tert-buty-4-methylphenol, and 2,4,6-tri-tert-butylphenol. The standard molar enthalpies of sublimation (or vaporization) of these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system. Molar enthalpies of fusionΔcrlHmo of the solid compounds were measured by d.s.c. Resulting values ofΔfHmo (g) were obtained at the temperature 298.15 K and used to derive strain enthalpies of alkylphenols. The intramolecular interactions were discussed in terms of the enthalpic contribution of the substituents. The buttress interaction of tert-alkyl groups with hydroxyl t-Bu-OH-t-Bu was found to be 5.0 kJ · mol−1. Other buttress effects of methyl, iso-propyl-, and tert-alkyl substituents with the OH-group were found to be negligible within ±(1 to 2)kJ · mol−1. These values provided a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.

Strain Effects in Phenyl-Substituted Methanes. Geminal Interaction between Phenyl and the Electron-Releasing Substituent in Benzylamines and Benzyl Alcohols

The standard (p° = 0.1 MPa) molar enthalpies of formation ΔfH°m(l) at T = 298.15 K of N,N-dimethylbenzylamine, α-methylbenzylamine, and α,α-dimethylbenzylamine were determined by means of combustion calorimetry. The standard molar enthalpies of vaporization of these compounds and also of benzylamine, benzyl alcohol, and α,α-dimethylbenzyl alcohol were obtained from the temperature dependence of the vapor pressure measured in a flow system. Resulting values of ΔfH°m(g) were obtained at T = 298.15 K and used to derive strain enthalpies of benzyl derivatives. The intramolecular interactions of the substituents were discussed in terms of deviations of ΔfH°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.

Strain effects in phenyl substituted methanes. Geminal interactions between phenyl and alkoxycarbonyl substituent

The standard ( p 0=0.1 MPa) molar enthalpies of formation Δ f H 0 m( l) at the temperature T=298.15 K were measured using combustion calorimetry for ethyl-2-phenyl-acetate, methyl-2-phenyl-propionate, and ethyl-2-phenyl-propionate. The standard molar enthalpies of vaporization of Δ g l H 0 m of these compounds were obtained from the temperature function of the vapour pressure measured in a flow system. Noticeable destabilized interactions of phenyl and alkoxycarbonyl substituents were derived from the enthalpies of formation in the gas phase of the compound under investigation. These values provide a further improvement to the group-contribution methodology for estimation of the thermodynamic properties of organic compounds

Thermochemistry of phenols: quantification of theortho-,para-, andmeta-interactions in tert-alkyl substituted phenols

The standard (po= 0.1 MPa) molar enthalpies of formation ΔfHmo(l or cr) at T=298.15 K were measured by means of combustion calorimetry for 2-tert-butylphenol, 2-tert-butyl-5-methylphenol, 2-tert-butyl-4-methylphenol, 2,4-di-tert-butylphenol, 3-tert-butylphenol, 4-tert-butylphenol, 2-methyl-4-tert-butylphenol, 4-tert-amylphenol, and 4-tert-octylphenol. The standard molar enthalpies of sublimation (or vaporization) of these compounds, and also of 2-tert-amylphenol, 2,4-di-tert-amylphenol, 2-tert-octylphenol, and 2,4-di-tert-octyl\\-phenol were obtained from the temperature dependence of the vapour pressure measured in a flow system. Molar enthalpies of fusion Δcr1Hmoof the solid compounds were measured by d.s.c. Resulting values of ΔfHmo(g) were obtained atT= 298.15 K and used to derive strain enthalpies of tert-alkylphenols. The intra-molecular interactions of the substituents were discussed in terms of deviations of ΔfHmo(g) from the group additivity rules. The interaction energy of the tert-alkyl and OH groups in the gas phase was found to be 12.5 kJ· mol−1for theortho-interaction, 1.7 kJ· mol−1for thepara-interaction, and 2.6 kJ· mol−1for themeta-interaction. These values provided a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.

Thermochemical investigation on α-methyl-styrene and parent phenyl substituted alkenes

The standard molar enthalpies of vaporization Δ g l H 0 m or sublimation Δ g cr H 0 m of α-methyl-styrene, 4-methoxy-α-methyl-styrene, 1,1-di-(4-methyl-phenyl)-ethene, allyl benzene, 1,2-dihydro-naphthalene, and 1,4-dihydro-naphthalene were obtained from the temperature function of the vapor pressure measured in a flow system. The standard ( p 0=0.1 MPa) molar enthalpies of formation Δ f H 0 m (l or cr) at T=298.15 K were measured using combustion calorimetry for α-methyl-styrene, 4-methoxy-α-methyl-styrene, and 1,1-di-(4-methyl-phenyl)-ethene. Molar enthalpies of fusion Δ l cr H 0 m of the solid compounds were measured by DSC. These experimental results together with the data available from the literature provided a coherent understanding of the energetics of phenyl-substituted species. The results of the study were also aimed at an improvement of the group-contribution methodology.

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 ΔfH°m (1 or cr) at the temperature T = 298.15 K were determined by using combustion calorimetry for α-ethyl-styrene (A), α-iso-propyl-styrene (B), α-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 Δ l g H°m or sublimation Δ 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 Δ cr l H°m of solid compounds were measured by d.s.c. Resulting values of ΔfH°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 ΔfH°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.

Thermochemistry of amines: strain in six-membered rings from experimental standard molar enthalpies of formation of morpholines and piperazines

The standard (p°=0.1 MPa) molar enthalpies of formation ΔfHm°(l) at the temperatureT=298.15 K were measured by means of combustion calorimetry for morpholine (A), N-methyl-morpholine (B), N-ethyl-morpholine (C), and N,N-dimethyl-piperazine (D). The standard molar enthalpies of vaporization ΔglHm° of these compounds and, in addition, the enthalpy of sublimation of piperazine (E) ΔgcrHm°=(72.1±1.3) kJ·mol−1, were obtained from the temperature dependence of the vapour pressure measured in a flow system. Strain enthalpies (ring-correction terms) of cyclic amines were derived from the measured enthalpies of formation of the gaseous compounds. These experimental results, together with data available from the literature, provided a quantitative understanding of the inter-relations of structure and energetics of amines and a further improvement of the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.

Thermochemical properties of branched alkylsubstituted benzenes

The standard (p°=0.1 MPa) molar enthalpies of formation ΔfHm° (l or cr) at the temperatureT=298.15 K were measured using combustion calorimetry for tert-butylbenzene, 4-methyl-1-tert-butylbenzene, 3,5-dimethyl-1-tert-butylbenzene, 5-methyl-1,3-di-tert-butylbenzene, and 1,4-di-tert-butylbenzene. The standard molar enthalpies of vaporization ΔlgHm°, or sublimation ΔcrgHm°, of these compounds, and also of 3-methyl-1-tert-butylbenzene, 1,3-di-tert-butylbenzene, and 1,3,5-tri-tert-butylbenzene were obtained from the temperature function of the vapour pressure measured in a flow system. Enthalpies of fusion ΔcrlHm° of solid compounds were measured by d.s.c. Strain enthalpies of branched alkylbenzenes were derived from the measured enthalpies of formation of the gaseous compounds. These experimental results, together with the data available from the literature, provided a quantitative understanding of the interrelations of structure and energetics of alkylbenzenes, and a further improvement on the group-contribution methodology for estimation of thermodynamic properties of organic compounds.

Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for Dicyclohexyl Sulfide, Diethylenetriamine, Di-n-octyl Sulfide, Dimethyl Carbonate, Piperazine, Hexachloroprop-1-ene, Tetrakis(dimethylamino)ethylene,N,N‘-Bis-(2-hydroxyethyl)ethylenediamine, and 1,2,4-Triazolo[1,5-a]pyrimidine

This paper reports measurements made for DIPPR Research Project 871 in the 1993 Project Year. The results of the study are aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic substances. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurements. Ideal-gas enthalpies of formation of hexachloroprop-1-ene, N,N‘-bis(2-hydroxyethyl)ethylenediamine, dimethyl carbonate, di-n-octyl sulfide, dicyclohexyl sulfide, diethylenetriamine, tetrakis(dimethylamino)ethylene, piperazine, and 1,2,4-triazolo[1,5-a]pyrimidine are reported. Enthalpies of fusion were determined for N,N‘-bis(2-hydroxyethyl)ethylenediamine, piperazine and 1,2,4-triazolo[1,5-a]pyrimidine. Two-phase (solid + vapor) or (liquid + vapor) heat...

Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for 2-Aminoisobutyric Acid (2-Methylalanine), Acetic Acid, (Z)-5-Ethylidene-2-norbornene, Mesityl Oxide (4-Methyl-3-penten-2-one), 4-Methylpent-1-ene, 2,2‘-Bis(phenylthio)propane, and Glycidyl Phenyl Ether (1,2-Epoxy-3-phenoxypropane)

The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurements. Ideal-gas enthalpies of formation of acetic acid, (Z)-5-ethylidene-2-norbornene, mesityl oxide (4-methyl-3-penten-2-one), 4-methylpent-1-ene, glycidyl phenyl ether (1,2-epoxy-3-phenoxypropane), and 2,2‘-bis(phenylthio)propane are reported. An enthalpy of formation of 2-aminoisobutyric acid (2-methylalanine) in the crystalline phase was determined. Using a literature value for the enthalpy of sublimation of 2-aminoisobutyric acid, a value for the ideal-gas enthalpy of formation was derived. An enthalpy of fusion was determined for 2,2‘-bis(phenylthio)propane. Two-phase (solid + vapor) or (liquid + vapor) heat capacities were determined from 300 K to the critical region or earlier decomposition temperature for all the compounds except acetic acid. For mesityl oxide and 4-methylpent-1-ene, critical temperatures and critical densities were determined from the DSC results and corresponding critical pressures derived from the fitting procedures. Group-additivity parameters and ring strain energies useful in the application of group-contribution correlations were derived.

A group contribution approach to predict permeability and permselectivity of aromatic polymers

Membrane separation of gases has evolved into an important separation technology for various gas mixtures (specifically O 2 N 2 ). Aromatic engineering polymers such as polysulfones, polycarbonates, and polyimides comprise commercially utilized membranes for these applications. The ability to predict permeability and permselectivity from polymeric structural units is highly desired in order to streamline synthetic approaches to optimum membrane candidates. A group contribution methodology is outlined in this paper which demonstrates excellent predictability of permeability (for O 2, N 2 and He) and good prediction of permselectivity for the O 2 N 2 and He N 2 gas pairs. This procedure utilizes the basic equation: ln P = Σ i=1 n φ i ln P i where φ i =volume fraction of a structural unit i and P i =the permeability contribution of the structural unit. Experimental permeability data are employed to set up an array of equations (of the above equation) solved by least squares fit. The values of φ i are calculated using computer software programs to predict molar volume contributions. The structural units are chosen around the chemical bond. This procedure shows promising results when applied to aromatic polymers chosen from the classes of polysulfones, polycarbonates, polyarylates, poly(aryl ketones) and poly(aryl ethers). This procedure has been utilized to determine the contributions of 24 structural units employing 65 polymers which comprise the database. Excellent agreement within the database is observed and good agreement outside the database is also demonstrated. This procedure allows for a quantitative assessment of the structure/permeability (permselectivity) relationships for polymers of interest for membrane separation, and thus demonstrates group contribution methodology can be applied to both polymer permeability and permselectivity. Further refinements by addition of other polymeric classes (e.g. polyimides and polyamides) as well as additional expansion of the database should prove to be a valuable technique to predict the membrane separation pottential of a wide variety of polymeric materials.

Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for Cyclohexene, Phthalan (2,5-Dihydrobenzo-3,4-furan), Isoxazole, Octylamine, Dioctylamine, Trioctylamine, Phenyl Isocyanate, and 1,4,5,6-Tetrahydropyrimidine

The results of a study aimed at improvement of the group-contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (dsc) heat-capacity measurements. Ideal-gas enthalpies of formation of cyclohexene, phthalan (2,5-dihydrobenzo-3,4-furan), isoxazole, octylamine, dioctylamine, trioctylamine, phenyl isocyanate, and 1,4,5,6-tetrahydropyrimidine are reported. Two-phase (liquid + vapor) heat capacities were determined for phthalan, isoxazole, the three octylamines, and phenyl isocyanate. Liquid-phase densities along the saturation line were measured for phthalan and isoxazole in the temperature range 298 K to 425 K. The critical temperature and critical density of octylamine were determi...

Mean field lattice equations of state

Abstract In preceding publications in this series, the Mean Field Lattice Gas (MFLG) model has been shown to produce a useful description of the pVT behavior of both polymers and low molar mass materials. Here we introduce a method, referred to as use of the Bondi constraint, by which the number of adjustable parameters required to apply the model can be reduced from five to three. This is accomplished by taking advantage of the general observations that (1) the parameter which represents the number of segments per molecule (or polymer repeat unit), m1, varies linearly with the van der Waals volume as calculated by Bondi and (2) the ratio of the molecular surface areas of a compound and a reference fluid, calculated from the MFLG parameters m1 and γ1, can be equated to the analogous ratio of surface areas calculated using Bondi's group contribution methodology. We show that this predictive method for derivation of the parameters m1 and γ1, produces a pVT description for ethane and ethylene which is comparable to that produced using the standard five-parameter fit. Thus the Bondi constraint is a useful means of generating material parameters that are necessary to apply the model to compounds for which few volumetric data are available.