Correlation of properties in hydrocarbons homologous series

Abstract

Correlations between combustible substances properties in the homologous series of n-alkanes and n-alcohols with a length of nС=1–20 were studied in order to determine ways to increase the methods convergence for assessing fire hazard parameters. The cluster length was added to the substance modulating parameters set. It should be noted that substances properties are often predicted using a molecule coarse-grained model, which has discreteness, does not describe short molecules, and requires an individual approach. It is shown that there are substance "arithmetic" parameters that directly depend on the certain atoms number. Among them, "length" better reflects isomeric, conformal, cluster differences, which are associated with parameters anomalies of hydrocarbons. A vaporization heat linear description from nС separately for n-alkanes and n-alcohols gives R=0,999. Exponential approximation of the n-alkanes boiling point tbp and flash point tfp by nС change fractions has R=0,999. It is shown that there is a correlation between tfp and tbp, but with a systematic difference, which indicates that the cluster composition is not completely similar at these temperatures; between tfp and tmp there is a smaller correlation, but its presence indicates clusters partial similarity. A universal formula for predicting hydrocarbons vaporization heats of 10 homologous series has been created, which has R=0,996. The description change hydrocarbons pulsations of in tmp was carried out on the cluster schemes alternation basis in homologous series, as well as taking into account their length and molar mass, which gives R=0,9997. According to similar principles, a formula for the hydrocarbons solubility in the water has been developed, which has the satisfactory accuracy. The study showed that the cluster length is a determining factor by which substance properties are modulated.