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)

Abstract

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.

The Guinness Molecules for the Carbohydrate Formula

“…Turning to thermodynamic reference values, the energies in Table must be corrected by −920 kJ/mol, the combined 0 K heat of formation for 2 CH 4 and 2 CO 2 . A rough experimental estimate of the 0 K heat of formation of acetic acid dimer yields −900 kJ/mol, in acceptable agreement with the CCSD(T) prediction of −908 kJ/mol, considering the simplifications involved in the dimer partition function and other experimental uncertainties for such anharmonic systems …”

“…Turning now to thermodynamic reference values, the energies in Table must be corrected by −460 kJ/mol, the combined 0 K heat of formation for CH 4 and CO 2 . For acetic acid, we determine the 0 K ideal gas heat of formation as −418 kJ/mol based on the 298 K heat of formation of −483.5 kJ/mol of the liquid, the monomer vaporization enthalpy of 51.6 kJ/mol, and the difference in thermal enthalpies between the elements and acetic acid of 14.1 kJ/mol . This, and even more so the ATcT values of −419.6 kJ/mol and −418.8 kJ/mol, compare well to our CCSD(T) value of −420 kJ/mol.…”

Liquid Densities and Excess Quantities for the Green Esterification Process

“…For the system of DES 1 + DES 2 , the curve trend shows both negative and positive deviations, and the values of excess molar volume shift from negative toward positive (Figure ). After x 1 = 0.5, the dispersive forces have acted in between the like molecules of the mixture giving a positive contribution . The maxima of negative deviation was at 0.1 mol fraction of DES 1 , and the maxima of positive deviation was at 0.9 mol fraction.…”

“…It can be noted from Table that the densities of individual components have the following pattern: acetic acid > n -butyl acetate > n -butanol, and the ILs and DESs follow the pattern [EMIM]­[HSO 4 ] > [EMIM]­[EtSO 4 ] > (ChCl–glycerol) > (ChCl–acetic acid) > [BMIM]­[OAc]. The individual compound density data reported in the literature, − experimental data, and COSMO-RS predicted density data are tabulated in Table . For DES 2 (ChCl–acetic acid), no literature reference was found.…”

“…After x 1 = 0.5, the dispersive forces have acted in between the like molecules of the mixture giving a positive contribution. 11 The maxima of negative deviation was at 0.1 mol fraction of DES 1 , and the maxima of positive deviation was at 0.9 mol fraction. This shows that as the composition of DES 1 increases in the system, dispersive forces became stronger within the like molecules of DES 1 and DES 2 mixtures.…”