The electrooptical properties of 4,4’-biscyanobiphenyloxyalkanes in dioxane and benzene were investigated by the method of equilibrium electric birefringence. A non-monotonic dependence of the Kerr molar constant of these compounds on the length of the oxyalkane spacer was found. This dependence is due to the influence of the odd-even effect on the intramolecular orientational polar and anisotropic order. The problems are discussed of the effect of equilibrium and kinetic spacer flexibility on the value and sign of the observed birefringence and on the degree of correlation in orientations of mesogenic chain fragments in an electric field.