Dielectric Study of Intermolecular Association in Isomeric Octyl Alcohols

Abstract

The equilibrium dielectric constants of eight liquid isomeric octanols have been measured over a wide range of temperature, and the data are analyzed in terms of the Kirkwood correlation factor. A simple molecular model based on hydrogen‐bond associative equilibria involving both ring dimers and linear chain n‐mers is developed. Equilibrium constants for ring and chain formation are deduced, and it is concluded that entropic factors, which can be correlated with the geometry of the molecules, are the principal basis for differences between isomers. At relatively high temperatures those species whose − OH group is most sterically blocked prefer to form rings, while those whose − OH group is relatively accessible tend to form open chains. In all cases, chains become the preferred species at low temperatures. $\mathrm{\Delta H°}$ for hydrogen‐bond formation in chains is estimated as about − 6.7 kcal/mole; for rings, about − 4.5 kcal/mole. $\mathrm{\Delta S°}$ varies from − 16 to − 30 eu/mole for chains and from − 13 to − 20 eu/mole for rings.