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. ΔH° for hydrogen-bond formation in chains is estimated as about − 6.7 kcal/mole; for rings, about − 4.5 kcal/mole. ΔS° varies from − 16 to − 30 eu/mole for chains and from − 13 to − 20 eu/mole for rings.

Measurements of static dielectric constant were made for all except t-butyl alcohol from the boiling points to —140°C; dispersion and loss were measured below 0°C in the range 20 cy/sec to 2 Mc/sec. Multiple dispersions were found as in other alcohols. The temperature dependences of static values are examined in terms of finite extent of chainwise molecular coordination by hydrogen bonding, and the rate laws of the dispersions are discussed.

Articles you may be interested inEffect of ions on intermolecular association and subT g dielectric relaxation in isomeric octanols Dielectric constant and loss have been measured in the frequency range 0.1-5X10 6 Hz over a wide range of temperature and pressures to 4 kbar for the following compounds: 2-octanol, 7-methyl-, 6-methyl-, 5-methyl-, and 2-methyl-3-heptanol. For each compound, most of the dispersion is well described by the Debye equation. At high frequencies additional regions of dispersion appear which could be resolved in three of the compounds. Activation parameters are derived for all of the compounds and are functions of pressure, temperature, and the nature of the alcohol's alkyl group. A qualitative model of dielectric relaxation based on ideas of Litovitz and Anderson and Ullman is proposed to explain the results.

The dielectric constants of the eight lowest aliphatic alcohols have been measured from room temperature to their respective critical temperatures. The densities were also measured if they were not previously available. The data were analyzed in terms of Kirkwood's correlation factor based on a model of linear, hydrogen-bonded chains with restricted rotation about the hydrogen bond and variable degree of polymerization. The equilibrium constants are strongly dependent on the size and shape of the alkyl group. —ΔF°298 (kcal/mole; mole fraction units), —ΔH°298 (kcal/mole), and —ΔS°298 (cal/mole·deg) for hydrogen-bond formation in the pure liquid are: MeOH, 3.95, 6.50, 8.56; EtOH, 4.10, 8.63, 15.2; n-PrOH, 3.42, 7.76, 14.6; iso-PrOH, 2.97, 8.64, 19.1; n-BuOH, 3.12, 7.70, 15.4; iso-BuOH, 2.87, 8.73, 19.7; sec-BuOH, 2.05, 7.97, 19.9; tert-BuOH, 0.98, 7.28, 21.2.