Question

Lower carboxylic acids are highly soluble in water. Explain.

Hint:

"Like dissolves like." Since water is polar and H-bonded, it dissolves other polar, H-bonding substances like lower carboxylic acids.

Answer 1

1. Lower carboxylic acids (like Methanoic acid, Ethanoic acid) have a polar carboxyl group (-COOH).
2. The oxygen atoms in the carboxyl group and the hydrogen atom of the -OH group can form hydrogen bonds with water molecules.
(R-COOH $\cdots$ OH$_2$)
3. This extensive hydrogen bonding allows the acid molecules to mix freely with water.
4. As the size of the hydrophobic alkyl chain (R) increases, the solubility decreases because the hydrophobic interaction overcomes the hydrogen bonding.