Ideal-gas enthalpies of formation of methyl benzoate, ethyl benzoate, (R)-(+)-limonene, tert-amyl methyl ether, trans-crotonaldehyde, and diethylene glycol are reported. The standard energy of combustion and hence standard enthalpy of formation of each compound in the liquid phase has been measured using an oxygen rotating-bomb calorimeter without rotation. Vapor pressures were measured to a pressure limit of 270 kPa or the lower decomposition point for each of the six compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperature (ambient to a maximum of 548 K). A differential scanning calorimeter was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. For methyl benzoate and tert-amyl methyl ether, critical temperatures and critical densities were determined from the DSC results and corresponding critical pressures derived from the fitting procedures. Fitting procedures were used to derive critical temperatures, critical pressures, and critical densities for each of the remaining compounds. The results of 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 region of the experimentally determined vapor pressures), and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. All measured and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each of the compounds studied. Group-additivity parameters, useful in the application of the Benson gas-phase group-contribution correlations, were derived.

This paper reports measurements made for DIPPR Research Project 821 in the 1996 Project Year. Vapor pressures were measured to a pressure limit of 270 kPa (unless decomposition occurred) for all six compounds using a twin ebulliometric apparatus. Additionally, for -caprolactam, measurements at low pressures (0.043 kPa to 3.08 kPa) were performed using an inclined-piston apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. A critical temperature and the corresponding critical density were determined experimentally for pyrazine. 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 (within the temperature range ((50 K) of the vapor pressures), enthalpies of fusion if solid at ambient temperature, solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using a four-term power series in [(1 -T r ) n/3 ]. For -caprolactam, the results of the present measurements were combined with literature values to derive a "Third Law" estimate of sublimation pressures in the region of ambient temperature. All measured and derived values were compared with those obtained in a search of the literature.

This paper reports measurements made for DIPPR Research Project 821 in the 1994 Project Year. Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for eight compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter (DSC) was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. Where possible, the critical temperature and critical density for each compound were determined experimentally. The results of the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization [within the temperature range (±50 K) of the vapor pressures], enthalpies of fusion if solid at ambient temperature, solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using a four-term power series in either T or [(1 − T r)1/3]. All measured and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each of the compounds studied. A “Rule-Of-Thumb” derived in the 1992 Project Year was used to estimate thermal decomposition temperatures by radical scission from a knowledge of the bond dissociation energy or vice versa.

This paper reports measurements made within the DIPPR‡ Project 821 for the 1992 Project Year. Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for eight compounds using an inclined-piston and twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperature (ambient to a maximum of 548 K). A differential scanning calorimeter (dsc) was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. Where possible, the critical temperature and critical density for each compound were determined experimentally. The results of 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 region of the experimentally determined vapor pressures], solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using extended corresponding states. All measured and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each of the compounds studied. The temperature at which initiation of thermal decomposition by a bond scission reaction occurs is discussed. A “Rule-Of-Thumb” is derived to estimate thermal decomposition temperatures by radical scission from a knowledge of the bond dissociation energy or vice versa. Compounds studied were acetophenone, (±)-1,2-butanediol, (±)-1,3-butanediol, diethylene glycol monopropyl ether, 1,3-dimethyladamantane, 2-ethoxyethyl acetate, ethyl octyl sulfide, and pentyl acetate.

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.