Why does trouton rule work

This is related to the ratio of the enthalpy of vaporization and the temperature of the transition:. Because of its convenience, the rule is used to estimate the enthalpy of vaporization of liquids whose boiling points are known. Thus is nothing unusual about K, but rather an influence from intermolecular interactions. For example, the entropies of vaporization of water, ethanol, formic acid and hydrogen fluoride are far from the predicted values. 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 greater, too.

The enthalpy of vaporization is greater for hydrogen-bonding molecules than for plain alkanes. For low-molecular weight alcohols, this effect is pronounced. The longer the alkane chain becomes, the more the compound behaves like a pure alkane. Keeping in mind the relative molecular weights of the compounds, you can see there is a decreasing effect of the hydrogen bonding and other effects on the n-alcohol series as we move to larger chains and become less alcohol-like structured liquid and more alkane-like unstructure liquid.

At the low-molecular weight end, hydrogen bonding dominates, so we see the behavior common to polar, hydrogen-bonding compounds.

At the high-molecular weight end, we see the pattern observed for alkanes. Learn more. Validity of Trouton's Rule Ask Question. Asked 7 years ago. Active 5 years, 1 month ago. Viewed 7k times. Improve this question. Freddy 4, 8 8 gold badges 37 37 silver badges 66 66 bronze badges. The GSE is derived by assuming that Trouton's rule is valid.

The GSE shows best results for small organic molecules termed "druglike". Add a comment. Active Oldest Votes. Improve this answer. Renato Renato 6 6 bronze badges. Please take a read them before posting further, and use correct punctuation and capitalization. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. Featured on Meta.