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 improvem ent 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 o f experimental data, are addressed by experimental studies of enthalpi es of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurement s. Ideal-gas enthalpies of formation of hexachloroprop-1-ene, N,N'-bis (2-hydroxyethyl)ethylenediamine, dimethyl carbonate, di-n-octyl sulfid e, dicyclohexyl sulfide, diethylenetriamine, tetrakis(dimethylamino)et hylene, piperazine, and 1,2,4-triazolo[1,5-alpha]pyrimidine are report ed. Enthalpies of fusion were determined for N,N'-bis(2-hydroxyethyl)e thylenediamine, piperazine and 1,2,4-triazolo[1,5-alpha]pyrimidine. Tw o-phase (solid + vapor) or (liquid + vapor) heat capacities were deter mined from 300 K to the critical region or earlier decomposition tempe rature for each compound studied. Liquid-phase densities along the sat uration line were measured for N,N'-bis(2-hydroxyethyl)ethylenediamine , dimethyl carbonate, and dicyclohexyl sulfide. For dimethyl carbonate and piperazine, critical temperatures and critical densities mere det ermined from the DSC results and corresponding critical pressures deri ved from the fitting procedures. Fitting procedures were used to deriv e critical temperatures, critical pressures, and critical densities fo r hexachloroprop-1-ene, di-n-octyl sulfide, dicyclohexyl sulfide, and diethylenetriamine. Group-additivity parameters and 1,4-interaction te rms useful in the application of group-contribution correlations were derived.