Relative permittivities, epsilon(r) and refractive indices, n(D), have been measured at (288.15-308.15) K and (293.15-303.15) K, respectively, for the mixtures 1-pentanol + octane, or + dibutyl ether and dibutyl ether + octane. These data have been used, together with density measurements available in the literature, to determine the correlation factor, g(k), for the studied systems according to the Kirkwood-Frohlich equations. Results show that the existence of cyclic species of 1-pentanol is predominant at low concentrations of this alkanol when is mixed with octane. These species are broken in large extent by the more active molecules of oxaalkane in the dibutyl ether mixture, which is in agreement with calorimetric data. The dibutyl ether + octane system does not show meaningful structure. These conclusions are confirmed by values of the molar polarization and by the temperature dependence of epsilon(r). The empirical expressions of Lorentz-Lorenz, Wiener, Heller, Gladstone-Dale and Newton correlate well the n(D) data. (C) 2012 Elsevier B.V. All rights reserved.