In this study, a detailed thermodynamic analysis of the ethyl tert-butyl ether (ETBE) synthesis reaction between tert-butyl alcohol (TBA) and ethanol is performed to determine a liquid phase equilibrium constant expression. The result is of practical significance in view of the imminent prominence of ETBE to be produced from TBA and ethanol, as a gasoline blending oxygenate. In this study, enthalpy of formation, Gibbs, enthalpy of vaporization, and heat capacities (as a function of temperature) of the reactants and products were estimated At 298 K, the standard molar enthalpy of reaction for ETBE from TBA and ethanol was found as - 1 23 kJ.mol(-1). The liquid phase nonideality of the system was tested, and it was found that the system approaches ideal conditions. The thermodynamic analysis approach given here is expected to be useful for other liquid-phase systems.