Validity of Trouton's Rule
The rule says that for many liquids the entropy of vaporization is almost the same, around ${\rm 85\,J K^{-1}} $.

The (partial) success of the rule is due to the fact that the entropy of a gas is so much larger than that of any liquid. Therefore, the entropy of the initial state (e.g. the liquid) usually makes no big difference.  However, if the liquid presents hydrogen bonding or any other kind of high ordered structure, its entropy will be particularly low and the entropy gain during vaporization will be larger than usual, too.