The physico-chemical aspects of some long straight chain alcohols from susceptibility measurement under a 24 GHz electric field at 25 °C

The straight line equation (χoij − χij′)/χij′ = ω(τ1 + τ2)(χij″/χij′) - ω2τ1τ2 for different weight fractions wj's of some dipolar long straight chain alcohols (j) in n-heptane (i) is derived from the available relative permittivities εij′, εij″, εοij and εαij at 25 °C under 24 GHz electric field. The intercepts and slopes of the above equation are used to get relaxation times τ1 and τ2 of the rotation of the flexible part and the whole molecule itself. χij′ (= εij′ − εαij) and χij″ (= εij″) are the real and imaginary parts of hf dimensionless complex dielectric orientational susceptibility χij⁎ and χoij (= εοij − εαij) is the low frequency dielectric susceptibility which is real. τj's of such alcohols are also measured from the ratio of the slopes of the individual variations of χij′ and χij″ with wj at wj→0 and the direct slope of χij″ versus χij′ equations of Murthy et al. [M.B.R. Murthy, R.L. Patil and D.K. Deshpande, Indian J. Phys 63B (1989) 491]. These τj's are finally compared with the reported τj's of Gopalakrishna [K.V. Gopalakrishna, Trans Faraday Soc. 53 (1957) 767] and τ1, τ2 by double relaxation method to see that the flexible part of the molecule is only rotating under the most effective dispersive region of the 24 GHz electric field. The weighted contributions c1 and c2 towards dielectric relaxations for estimated τ1, τ2 are, however, obtained from Fŕóhlich's theoretical formulations of χij′/χoij and χij″/χoij to compare them with those of graphical ones of (χij′/χoij)wj→0 and (χij″/χoij)wj→0. The latter ones are used to get the symmetric distribution parameter γ to have the symmetric relaxation times τs. The arbitrary curve of (1/ϕ) log cosϕ against ϕ in degree together with (χij′/χoij)wj→0 and (χij″/χoij)wj→0 experimentally obtained gives the asymmetric distribution parameter δ to get the characteristic relaxation time τcs. All these findings finally establish the symmetric relaxation behaviour for such compounds. The dipole moments μ1 and μ2 for the flexible part and the whole molecule are determined from τ1 and  τ2 and the linear coefficient β of χij′ versus wj's curves. All the measured μj's are compared with the reported μj's and μtheo's derived from the bond angles and bond moments of the substituted polar groups of the compounds to arrive at the physico-chemical properties by the conformations sketched in the paper. The slight disagreement of estimated μj's and μtheo's is, however, explained with the consideration of inductive and mesomeric moments in addition to strong hydrogen bonding of the flexible polar groups attached to the parent molecule.