784
MCCULLOUGH, FINKE,HUBBARD, TODD, MESSERLY, DOUSLIN AND WADDINGTON
Vol. 65
THERMODYKAMIC PROPERTIES OF FOUR LINEAR THIAALKANES' BY J. P. MCCULLOUGH, H. L. FINKE, W. N. HUBBARD, S. S. TODD, J. F. MESSERLY,D. R. DOUSLIN AND GUYWADDINGTON contribution No. 9Y from the Thermodynamics Laboratory, Petroleum Research center, Bureau of Mines, the Interior, Bartlesvilk, Oklahoma
u. 8. Department of
Received October 86, 1980
Values of heat capacity, heat of fusion, entropy and related thermodynamic properties of 2- and 3-thiahexane, Cthiaheptane and Etthianonane were determined by low temperature calorimetric measurements in the range 11-370°K.; the heats of combustion were determinedoby rotating-bomb calorimetry, The vapor pressure of 2-thiahexane waa measured ebullioResults of these studies were used in calculating values of entropy, heat of formation, metrically in the range 73-163 free energy of formation and equilibrium constant of formation in the standard liquid and gas states a t 298.15"K. For addition of a methylene group to a normal propyl or larger normal alkyl group in linear thiaalkanes, the increments to the thermodynamic properties were found the same as those in normal alkanes above n-heptane.
.
Since 1948, the Bureau of Mines has made thermodynamic studies of selected organic sulfur compounds as part of American Petroleum Institute Research Project 48A. The object is to obtain information about the change in thermodynamic properties with molecular size and shape for use in calculating, by incremental methods, tables of data for entire homologous series of sulfur compounds. For example, the results obtained in individual studies of 16 compounds were used recently in preparing comprehensive tables of data for 100 linear alkane thiols, sulfides and symmetrical disulfides, through the CZ0compound in each clam2 This paper reports basic data for 2- and 3-thiahexane, 4-thiaheptane and 5-thianonane. The results given here and similar data previously reported for 2-thiapro~ane,~ 2 - t h i a b ~ t a n e ,2-thia~ pentane6 and 3-thiapentanee were used in computing some of the data in ref. 2. The Experimental section gives detailed results of low temperature and combustion calorimetric studies of 2- and 3-thiahexane1 4-thiaheptane and 5-thianonane and vapor pressure studies of 2thiahexane. Vapor pressure data for the other three compounds were reported previously by White, Barnard-Smith and Fidler their results were recorrelated by the Cox equation,s which is better for extrapolation to low temperatures than the Antoine equation used in ref. 7. These results were used in computing values of the standard entropy and heat of vaporization and of the standard entropy, heat of formation, free rnergy of formation and equilibrium constant of formation in the liquid and gas states a t 298.15"1
