Estimation of Latent Heat for Hydrocarbons by Means of Raman Frequencies

Abstract

EARLIER studies1–5 have shown a correlation between the Raman spectra and boiling points of normal and substituted hydrocarbons. A direct linear relation has also been established between the reduced vaporization energy change δ(ΔH)/RTB of benzene and its substituted homologues ((C6H5X, where X=F, Cl, Br, 1) as well as of normal and substituted hydrocarbons (my unpublished work) and the X-sensitive6 or, in the case of hydrocarbons, the skeletal deformation frequencies, ℏcv/kTB, at their normal boiling point temperatures. The authors of refs. 1–6 have also pointed out that the existence of such correlations might be helpful in the formulation of a quantum theory of the vaporization process. In other words, it seems possible to propose a mechanism of evaporation on the basis of the thermally excited vibrational state of molecule as against the mechanism of evaporation using only the kinetic theory of liquids (for instance, the postulate that the evaporation process is essentially controlled by the molecular rotational partition function7–9).