Determination of self-association equilibrium constants of ethanol by FTIR spectroscopy

The self-association of ethanol diluted in CCl4 has been studied by IR spectroscopy, Three OH stretching bands were assigned to monomers, linear dimers, and linear multimers. The self-association was described with two equilibrium constants, one for the formation of dimers, K-2, the other for the formation of multimers, K-A. These equilibrium constants were determined for ethanol concentration ranging from 0.19 to 0.76 mol L(-1) by using a method developed by Coggeshall and Saier. At T = 25 degrees C, K-2 was found to be equal to 1.08 L mol(-1) in terms of molar concentration or 18.3 in terms of molar fraction; K-A was found to be equal to 3.52 L mol(-1) in terms of molar concentration or 60.0 in terms of molar fraction. The enthalpy of formation for K-2 was found to be equal to -4.61 kcal mol(-1) and to -4.15 kcal mol-l for K-A.