∆𝑆 𝑚 = 56.5 -𝑅𝑙𝑛𝜎 (J K -1 mol -1 ) (1) The significant intuitive appeal of the above explanation comes from its conceptual and numerical arguments being valid and entirely consistent. However, the same account fails to explain a widespread observation: Symmetrical molecules, which, as a general rule, do have higher melting temperatures, quite often have greater melting entropies than their less symmetrical isomers. Therefore, Gilbert introduced the effect of "entropy-enthalpy compensation" into Eq. 1, namely that ΔSm is dependent upon the enthalpy of melting ΔHm. `Flexible' molecules (potentially multi-conformational) tend to yield higher values of ΔSm for a given ΔHm than `rigid' ones.