what is the reason for the solubility or insolubility of alcohols

Question

anonymous · Answer

the length of the hydrocarbon chain i guess..
as it increases, the solubility decreases because of the hydrogen bond to the water molecules.. something like that. i don't remember O.o

kkutie7 · Answer

http://www.chemguide.co.uk/organicprops/alcohols/background.html read up

kkutie7 · Answer

it says towards the bottom it has to do with the carbon chain. It gives more detail than I can at the moment. Scroll to about a fourth of the way down.

toxicsugar22 · Answer

does it have to do with the polarity of alcohol

anonymous · Answer

?

matt101 · Answer

Everyone is sort of on the right track. I'm assuming we're talking about solubility in water. A general solubility rule is like dissolves like (i.e. polar solutes dissolve more easily in polar solvents, and nonpolar solutes dissolve more easily in nonpolar solvents).

An alcohol is a molecule containing an -OH group. The -OH group is extremely polar and in fact capable of forming hydrogen bonds, which are relatively strong intermolecular bonds. Water forms hydrogen bonds with itself, but the alcohol can compete with its own hydrogen bonds and this is what allows it to dissolve.

However, as you start extending the hydrocarbon chain, the alcohol becomes more and more nonpolar (remember, plain hydrocarbons are hydrophobic). Hydrophobic molecules interact with each other via London dispersion (van der Waals) forces, which are extremely weak and can't compete with the strong hydrogen bonds formed within water. This means the water molecules will continue interacting with each other, and "ignore" the long-chain alcohol, making this molecule insoluble in water.

I hope that makes sense - please ask if anything is unclear!