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

Abstract

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, vaporpressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurements. Enthalpies of formation in the condensed phase were determined for 1,4-diisopropylbenzene, 1,2,4,5tetraisopropylbenzene, dimethyl malonate, glutaric acid, pimelic acid, and cyclohexanone oxime. Idealgas 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 capacities were determined from 300 K to the critical region or earlier decomposition temperature for all the title compounds. For 1,4-diisopropylbenzene, 1,2,4,5-tetraisopropylbenzene, and dimethyl malonate, values of the critical temperature and critical density were determined from the DSC results and the corresponding critical pressure was derived from the fitting procedures. The results of all the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization (restricted to within (50 K of the temperature range of the vapor pressures), and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. Enthalpies of sublimation were derived for cyclohexanone oxime and, using literature vapor pressures, glutaric acid. Group-additivity enthalpy of formation parameters and strain energies useful in the application of ideal-gas-phase group-contribution correlations were derived. Errors in the literature data for the enthalpy of formation of diethyl malonate are noted.

From a eutectic mixture to a deep eutectic system via anion selection: Glutaric acid + tetraethylammonium halides

“…The β→α transition temperature (343.8±0.8 K) and enthalpy (2.46±0.10 kJ • mol −1 ) are in agreement with literature values, considering the transition temperature is sensitive to the applied heating rate. The GluA melting point (369.0 K) was slightly lower than that reported in literature (370.9-372.2 K), while the enthalpy of fusion (21.2±1.0 kJ • mol −1 ) matched literature values (19.8-23 kJ • mol −1 ) 12,26,38,39 . The GluA was extensively dried but not recrystallised before use, which might be necessary for a higher onset temperature.…”

“…for which the values of parameters A L i , A S i , B L i , and B S i were adopted from literature 26 . For the salts Eq.…”

“…To elucidate this shift, the S-L phase diagrams of GluA + Et 4 NCl, GluA + Et 4 NBr, and GluA + Et 4 NI were constructed experimentally over a broad composition range using a wide variety of analysis techniques. Additionally, the solid phase was evaluated using wide-angle X-ray scattering (WAXS) at miscellaneous temperatures and compositions, since both GluA and Et 4 NX are polymorphic materials [26][27][28][29] and can form co-crystals [18][19][20][21][22][23]30 . The resulting phase boundaries were described quantitatively using various suitable thermodynamic models 31,32 .…”

Experimental and Theoretical Study of the Structures and Enthalpies of Formation of the Synthetic Reagents 1,3-Thiazolidine-2-thione and 1,3-Oxazolidine-2-thione

“…In some instances, a group value is derived from a single thermochemical measurement of a compound containing that group. In such cases in the literature, sometimes the group increment has been derived, e.g., (C) 2 CNOH from cyclohexanone oxime, 9 while in others the compound stands in splendid isolation, such as saccharin from which the acylsulfonamide functional group and the associated (C b )CONHSO 2 (C b ) group increment was not derived. 10 In this latter case, the acylsulfonamide group is found in a five-membered ring that plausibly introduces additional ring strain.…”

Enantiotropic phase transition and twinning in 2,2,3,3,4,4-hexafluoropentane-1,5-diol

“…29.7 (3) kJ mol À1 . The observed enthalpy change for the solidstate phase transition is relatively small compared with other organic crystal structures (Yu et al, 2000;Cingolani & Berchiesi, 1974;Petropavlov et al, 1988;Steele et al, 2002). Typical values of enthalpy changes for similar phase transitions fall in the range 1-10 kJ mol À1 , which is larger than the observed enthalpy change from phase (II) to (I) of HFPD.…”