THE THERMODYNAMIC PROPERTIES OF CHROMAN AND ISOCHROMAN

Measurements leading to the calculation of the ideal-gas thermodynamic properties for chroman and isochroman are reported. Thermochemical and thermophysical properties were determined by adiabatic heat-capacity calorimetry, combustion calorimetry, comparative ebulliometry, and inclined-piston manometry. Density measurements are reported for chroman. Results were used to calculate standard molar entropies, enthalpies, and Gibbs energies of formation for the ideal gas at selected temperatures from near the respective triple-point temperatures to 500 K. The polynomial used in the JANAF Thermochemical Tables to represent the enthalpy of reference-state graphite from 298.15 K to 6000 K is published for the first time. Below 298.15 K, interpolated values used at NIPER are listed at 10 K intervals to 200 K. Published estimates of the ideal-gas properties of chroman and isochroman, based on group-contribution estimates, show large deviations from the experimental values reported here. © 1990.