Explain why Alkanes with odd number of carbon atoms possess lower boiling points than those having even number of carbon atoms

Explanation

The melting point of solids depends on the way the molecules are packed in the crystals.
The carbon atoms in alkanes are arranged in zig-zag type of chain and not as straight chain.
In n-alkanes with even number of carbon atoms, the terminal methyl group lies on the opposite sides of the zig-zag chain.
While with odd number of carbon atoms, the terminal methyl group lies ont eh same side of the zig-zag chain.
Therefore, n-alkanes having odd number of carbon atoms are more unsymmetrical and do not pack well in the crystal lattice.
Hence, less energy is required to break the crystal lattice and melt the solid. While, n-alkanes having even number of carbon atoms are symmetrical and are very well packed in the crystal lattice. Therefore, more energy is required to break the crystal lattice and melt the solid. That.s why alkanes with odd number of carbon atoms possess lower boiling points than those having even number of carbon atom