ASLevel help

Both ethanol and water contain hydrogen bonds. By considering the hydrogen bonding on these 2 solvents, suggest why 2-chlorobutane is more soluble in ethanol than water


any ideas? thanks

why is NaCl soluble in water but not in non-polar solvents like benzene or toluene?

Another way to phrase the question would be: Why is the attraction between 2-chlorobutane and ethanol greater than the attraction between 2-chlorobutane and water?

I am not sure
why is it?

It has to do with electrostatic attractions (polarity). 3-chlorobutane is rather non-polar and would most likely form Van der Waals' bonds to other molecules.

Water, on the other han, is very polar because it's such a small molecule and has two dominant polar sides, caused by the difference in electronegativity between the oxygen atom and the hydrogen atoms (this is why hydrogen bonds are strong). Since 3-chlorobutane is non-polar, it won't be attracted to the water. You can think of it as a charged molecule trying to bind electrostatically to a neutral one.

Although ethanol also has a hydrogen bond, it is a much longer molecule than water and the CH-chain is relatively non-polar. Because of that, the polarity of ethanol is a lot less than that of water. This means that ethanol would also form Van der Waals' bonds to other molecules. Hence, the attraction between the ethanol and the 3-chlorobutane would be greater than the attraction between water and the 3-chlorobutane, since ethanol and 3-chlorobutane can form Van der Waals' forces with each other. Consequently, it dissolves more in ethanol.

This is usually summarized as:

Polar molecules dissolve polar molecules.
Non-polar molecules dissolve non-polar molecules.

Note: you might be more familiar with the term (London) Dispersion Forces than Van der Waals' forces, but it's the thing.