Why are some alcohols soluble in water?

1 Answer
Sep 23, 2016

Because to a first approximation, the smaller alcohols are half a water molecule.


Methanol and ethanol are infinitely miscible in water. This reflects the capacity of the alcohols to hydrogen bond, and also the shortness of the hydrocarbyl tail. Propanol and the higher alcohols have limited solubility in water, in that interaction between the hydrophobic tails becomes the important interaction.

Here is something else to consider. And this also reflects the influence of the phenomenon of hydrogen bonding. Ethanol and hexanes are infinitely miscible. Methanol and hexanes are IMMISCIBLE: i.e. methanol and hexanes would form 2 separate layers. Can you advance a rationalization?