Untersuchungen zur Ermittlung von Assoziationskonstanten aus infrarotspektroskopischen Messungen an Alkoholen

Abstract

Infrared-spectroscopic measurements on the free OH absorption band of isopropanol, t-butanol and t-pentanol using various concentrations in CCl 4 and various temperatures, showed that the fraction α of the non-associated alcohol molecules was dependent on the concentration. Five different association models were used for calculating the formation constants of the single species. Within the limits of the accuracy of the measurements the values of α found as a function of concentration at various temperatures may be described by several contradictory models. Agreement between experiment and model may thus be accidental. Many errors and disagreements in the interpretation of association published in former studies, are comprehensible for this reason. In addition to the dimer absorption band near 3500 cm −1, these results support the view that with alcohols only a general association model with all species present is correct up to a definite maximum magnitude, and that special hypotheses concerning the value of the single formation constants may at best be considered as rough approximations.