Reason for decreased boiling point of hexafluoroisoproponal?

Question

Ethanol and isopropyl alcohol have boiling points 78.37 °C and 82.6 °C respectively. The increase in the boiling point is obvious due to increase in carbon chain length which resulted in increase in boiling point of isopropyl alcohol.

But recently, I come across fluorinated ethanol and isopropanol, and the trend of boiling point is the reverse. Trifluoroethanol has boiling point 78 °C whereas hexafluoroisopropanol has boiling point 58.2 °C.

what is the reason for the decrease in boiling point of hexafluoroisopropanol? Is it due to increase in the number of fluorine atom, if so then why this resulted in decrease in the boiling point?

Answer 1

Since fluorine is so much more electronegative than hydrogen, its electrons are considerably less polarizable. This decreases the extent to which induced dipoles are able to form (London dispersion forces), which in turn lowers the energy necessary to break the intramolecular forces. This is what gives fluorocarbons lower boiling points than their hydrocarbon counterparts.