3-Methyl-2-thiabutane: Calorimetric Studies from 12 to 500°K.; the Chemical Thermodynamic Properties from 0 to 1000°K.1

Abstract

The chemical thermodynamic properties of 3-methyl-2-thiabutane were investigated between 0 and 1000/sup 0/K. Low temperature calorimetric studies were made from 12 to 344/sup 0/K, and values were obtained of the heat capacity in the solid and liquid states (C/sub satd/), the heat of fusion (2236 cal. mole/sup -1/ at the triple point, 171.65/sup 0/K), and the entropy of the liquid at saturation pressure at 298.16/sup 0/K, 62.88 cal. deg./sup -1/ mole/sup -1/. From flow calorimetric studies, there were obtained values of the heat of vaporization (..delta..H/sub v/), heat capacity in the ideal gaseous state (C/sup 0//sub p/), and the second virial coefficient (B = V(PV/RT - 1)). Some of the results are represented by the following empirical equations: (A) C/sub satd/(liq.) = 50.83 - 0.16245T + 5.951 x 10/sup -4/ T/sup 2/ - 5.318 x 10/sup -7/ T/sup 3/, cal. deg./sup -1/ mole/sup -1/ (177 to 344/sup 0/K); (B) ..delta..H/sub v/ = 10.761 - 4.661 T - 0.01369 T/sup 2/, cal. mole/sup -1/ (318 to 358/sup 0/K); (C) C/sup 0//sub p/ = 3.78 + 9.489 x 10/sup -2/ T - 3.944 x 10/sup -5/ T/sup 2/, cal. deg./sup -1/ mole/sup -1/ (347 to 500/sup 0/K); and (D) B = 211more » - 147.0 exp (800/T), cc. mole/sup -1/ (318 to 500/sup 0/K). The entropy in the ideal gaseous state at 298.16/sup 0/K, 85.87 cal. deg./sup -1/ mole/sup -1/, and the standard heat of formation from graphite, hydrogen and gaseous diatomic sulfur, -36.83 kcal. mole/sup -1/ at 298.16/sup 0/K, were computed from these data and heat of combustion data to be reported elsewhere. Values of the functions (F/sup 0/ - H/sub 0//sup 0/)/T, H/sup 0/ - H/sub 0//sup 0//T, S/sup 0/ and C/sup 0//sub p/ were computed from spectroscopic and molecular structure information. The parameters required to describe restricted internal rotation and to evaluate anharmonicity corrections were chosen to give agreement between calculated and experimental values of the entropy and vapor heat capacity. Values of the heat, free energy and equilibrium constant of formation of 3-methyl-2-thiabutane were computed.« less