Oscillation and Stepwise of Hydrocarbon Melting Temperatures as a Marker of their Cluster Structure

Abstract

The presence of melting temperatures oscillatory and stepwise changes for hydrocarbons four homologous series is demonstrated and analyzed. The oscillating dependence is manifesteds on the principle of «even-odd» molecules with different deviations from linearity. According to the working hypothesis, this is due to the presence of the matter smallest structural unit in the cluster form of with a certain coordination number. The oscillation of melting temperatures in hydrocarbons series is explained by the fact that clustering can occur both at the site of the final carbon in the molecule and at other carbons in the molecule chain, and this fact depends on the «even-odd» effect. Based on the known values of melting temperatures in homologous series, the clusters probable structure is assumed. It is shown that graphs for the calculated values of equivalent lengths of these clusters correlate with corresponding graphs for hydrocarbons melting temperatures. An approximation formula has been developed to predict melting temperatures of hydrocarbons based on the values of the equivalent length and the cluster molecular weight, which operates with an approximation coefficient of 0.997 and a mean deviation of 4.2 K.