Ideal gas thermodynamic properties of simple alkanols

Abstract

The ideal gas thermodynamic properties [C p 0 , S0(T) −S0(0) and H0(T)-H0(0)] of methanol (CH3OH), ethanol (C2H5OH), 1-propanol (CH3CH2CH2OH), and 2-propanol [(CH3)2CHOH] over the temperature range 0 to 1500 K at 1.01325-bar (1-atm) pressure are calculated by the statistical mechanical method, employing the recent molecular and spectroscopic constants. The internal rotational contributions to the thermodynamic properties caused by the presence of -CH3, -C2H5, and -OH rotors in these molecules are evaluated using an internal rotational partition function formed by the summation of internal rotational energy levels for each rotor. In the calculation of the thermodynamic properties of ethanol (g) and 1-propanol (g), we adopted a molecular model that the vapor of each compound contains an equilibrium mixture of trans and gauche isomers. The existence of such isomers was observed spectroscopically in recent years. Our calculated results, such as C p 0 and S0(T) ****-S0(0), agree with available experimental values.