The vapor heat capacities of ethyl alcohol have been measured, as a function of pressure, at 368, 422, and 476deg;K. From the variation of the heat capacity with pressure, together with vapor densities calculated by the Clapeyron equation, an equation of state for ethyl alcohol has been obtained. This equation has been used to extrapolate the measured heat capacities to the ideal gas state and likewise to correct the observed entropy.The infrared spectra of vapor C2H5OH, C2H5OD, and liquid C2H5OD are presented and a vibrational assignment is obtained which is sufficiently reliable for the statistical calculation of the thermodynamic properties.Comparison of the observed and statistically calculated heat capacities and entropies shows that, with a barrier to internal rotation of the CH3group of 3000 calories, the rotation of the OH group is hindered by a barrier between 0 and 1200 calories. Most satisfactory agreement is obtained for CH3and OH barriers of 3300 and 800 calories, respectively. Furthermore, comparison of the observed and calculated equilibrium constants for the reactionC2H4lpar;grpar;plus;H2Olpar;grpar;rlhar2;C2H5OHlpar;grpar;supports the selection of fundamental frequencies and internal rotation barriers.
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