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

Abstract

The straight line equation ( χ oij − χ ij′)/ χ ij′ = ω( τ 1 + τ 2)( χ ij″/ χ ij′) – ω 2 τ 1 τ 2 for different weight fractions w j's of some dipolar long straight chain alcohols (j) in n-heptane (i) is derived from the available relative permittivities ε ij′, ε ij″, ε οij and ε αij at 25 °C under 24 GHz electric field. The intercepts and slopes of the above equation are used to get relaxation times τ 1 and τ 2 of the rotation of the flexible part and the whole molecule itself. χ ij′ (= ε ij′ − ε αij) and χ ij″ (= ε ij″) are the real and imaginary parts of hf dimensionless complex dielectric orientational susceptibility χ ij ⁎ and χ oij (= ε οij − ε αij) is the low frequency dielectric susceptibility which is real. τ j's of such alcohols are also measured from the ratio of the slopes of the individual variations of χ ij′ and χ ij″ with w j at w j→0 and the direct slope of χ ij″ versus χ ij′ equations of Murthy et al. [M.B.R. Murthy, R.L. Patil and D.K. Deshpande, Indian J. Phys 63B (1989) 491]. These τ j's are finally compared with the reported τ j's of Gopalakrishna [K.V. Gopalakrishna, Trans Faraday Soc. 53 (1957) 767] and τ 1, τ 2 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 c 1 and c 2 towards dielectric relaxations for estimated τ 1, τ 2 are, however, obtained from Fŕóhlich's theoretical formulations of χ ij′/ χ oij and χ ij″/ χ oij to compare them with those of graphical ones of ( χ ij′/ χ oij) w j→0 and ( χ ij″/ χ oij) w j→0 . The latter ones are used to get the symmetric distribution parameter γ to have the symmetric relaxation times τ s. The arbitrary curve of (1/ ϕ) log cos ϕ against ϕ in degree together with ( χ ij′/ χ oij) w j→0 and ( χ ij″/ χ oij) w j→0 experimentally obtained gives the asymmetric distribution parameter δ to get the characteristic relaxation time τ cs. All these findings finally establish the symmetric relaxation behaviour for such compounds. The dipole moments μ 1 and μ 2 for the flexible part and the whole molecule are determined from τ 1 and τ 2 and the linear coefficient β of χ ij′ versus w j's curves. All the measured μ j's are compared with the reported μ j's and μ theo'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 μ j's and μ theo'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.