Ethanethiol (Ethyl Mercaptan): Thermodynamic Properties in the Solid, Liquid and Vapor States. Thermodynamic Functions to 1000°K.1

Abstract

The thermodynamic properties of ethanethiol have been measured in the solid, liquid and vapor states over the temperature range 14 to 450/sup 0/K. The entropy of the saturated liquid at 298.16/sup 0/K was derived from measurements of the heat capacity of the solid and liquid and the heat of fusion (1189 cal. mole/sup -1/ at the triple point, 125.26 +- 0.05/sup 0/K). Results obtained for the vapor pressure, heat of vaporization (..delta..H/sub vap./), vapor heat capacity in the ideal gaseous state (C), and second virial coefficient (B, in the equation of state, PV = RT + BP) are accurately represented by the empirical equations (1) log P = 6.96206 - 1084.531/(t + 231.385), (P, mm.; t, /sup 0/C.); (2) ..delta..H/sub vap./ = 8151 + 1.369T - 0.02288T/sup 2/, cal. mole/sup -1/ (280 to 308/sup 0/K); (3) C/sup 0//sub p/ = 4.45 + 4.836 x 10/sup -2/ - 1.695 x 10/sup -5/T/sup 2/, cal. deg./sup -1/ mole/sup -1/ (315 to 450/sup 0/K); (4) B = -27 - 60.1 exp(800/T), cc. mole/sup -1/ (280 to 450/sup 0/K). The entropy of the ideal gas at one atmosphere pressure and 298.16/sup 0/K (70.77 +- 0.15 cal. deg./sup -1/ mole/sup -1/) was computed from thesemore » data. A vibrational assignment was made for ethanethiol, based upon information from similar molecules. The heights of the potential barriers to internal rotation selected to fit the experimental thermal data were 3310 cal. mole/sup -1/ for the methyl barrier and 1640 cal. mole/sup -1/ for the thiol barrier. Values of the free energy function, heat content, entropy and heat capacity were computed on the basis of an harmonic-oscillator, rigid-rotator approximation at selected temperatures up to 1000/sup 0/K.« less