Revealing generality of the thermodynamic properties for crystals of long-chain aliphatics and polymethylene

We analyze the dependency of melting points of molecular crystals with different chain lengths on the crystal habit of elementary volume for the first-order phase transition. We demonstrate that molecular crystals with identical chemical structure of their cores–unbranched alkanes $\{$CH$_{3}$(CH$_{2}$)$_{n}$CH$_{3}\}$, diols $\{$COH(CH$_{2}$)$_{n}$COH$\}$, unbranched aliphatic alcohols $\{$CH$_{3}$(CH$_{2}$)$_{n}$COH$\}$, saturated carboxylic acids $\{$CH$_{3}$(CH$_{2}$)$_{n}$COOH$\}$, and dicarboxylic acids $\{$COOH(CH$_{2}$)$_{n}$COOH$\}$–lose their identity and individual properties and evolve toward polyethylene as the number of repeating–CH$_{2}$–groups increases.