D. W. Scott

Cyclohexanethiol and 2,4‐Dimethyl−3‐thiapentane: Molecular Vibrations, Conformational Analyses, and Chemical Thermodynamic Properties

Statistical thermodynamic treatments were made of the conformational energetics of the cyclohexanethiol and 2,4‐dimethyl−3‐thiapentane molecules. For cyclohexanethiol, there are 24 conformations that arise from the chair—skew‐boat and equatorial—axial equilibria of the frame and different orientations of the thiol group. The equatorial‐chair conformation is the most stable; the axial‐chair conformation has about 1.1 kcal/mole greater energy. For 2,4‐dimethyl−3‐thiapentane, six conformations could arise from different orientations of the isopropyl groups; however, only a d—l pair that involves no methyl—methyl interaction between the isopropyl groups has appreciable stability. Vibrational assignments needed for each compound were obtained by interpreting the molecular spectra for the vapor, liquid, and crystal states with the guidance of force‐constant calculations. Tables of the chemical thermodynamic properties were compiled.

The Heat Capacity of Benzene Vapor. The Contribution of Anharmonicity

The heat capacity of benzene vapor was measured at two or more pressures at each of five temperatures in the range 68° to 198°C; and values of Cpo, the heat capacity in the ideal gas state, were obtained. By assuming a moderate degree of anharmonicity of the vibrations, it was possible to obtain excellent agreement between values of Cpo calculated statistically from spectroscopic data, and the observed values. An empirical equation for the second virial coefficient of benzene vapor was obtained from the observed values of (∂Cp/∂P)T, and heat of vaporization and vapor pressure data.