Predict the relative solubility of the following pairs of compounds in aqueous solvent and arrange the two compounds of each pair in order of increasing solubility.
Remember that "like dissolves like" when it comes to solubility. Water is a highly polar solvent, so compounds that are more polar will dissolve better in it than less polar compounds.
The first pair of compounds are benzene and benzoic acid. The carboxylic acid in benzoic acid makes it much more polar than benzene, so benzoic acid will have a much higher solubility in water than benzene.
The second pair of compounds are acetic acid and methyl acetate. The carboxylic acid in acetic acid is more polar than the ester functionality in methyl acetate, so acetic acid will be more soluble in water than methyl acetate.
The final pair of compounds are 2-butanol and 2-butanone. 2-Butanol contains an alcohol while 2-butanone contains a ketone. Alcohols are more polar than ketones, so 2-butanol will more more soluble in water than 2-butanone.
Arranging the pairs in terms of increasing aqueous solubility:
1) benzene, benzoic acid
2) methyl acetate, acetic acid
3) 2-butanone, 2-butanol