The melting points of linear alkanes exhibit a non-monotonic dependency on molecular weight and chain length parity due to variations in crystal lattice packing efficiency rather than van der Waals forces alone. Specifically, transitions between odd-numbered carbon chains (where molecules pack less efficiently) and even-numbered chains (which allow denser lamellar stacking via methylene group alignment) result in significant enthalpic jumps that diminish as the chain length increases to infinity. This phenomenon illustrates how intermolecular structural periodicity governs phase transition temperatures within homologous series, distinguishing thermal behavior from simple boiling point trends which correlate directly with molecular mass.
The melting points of linear alkanes exhibit a non-monotonic dependency on molecular weight and chain length parity due to variations in crystal lattice packing efficiency rather than van der Waals f…