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 HOC(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 HOOC(CH 2 ) n COOH—lose their identity and individual properties and evolve toward polyethylene as the number of repeating–CH 2 –groups increases.