Why are low-molecular-weight alcohols highly soluble in water?

Low-molecular-weight alcohols are highly soluble in water primarily due to the presence of the hydroxyl group (—OH). This functional group is hydrophilic, or "water-loving," because it is capable of forming hydrogen bonds with water molecules.12

Because water molecules also contain hydroxyl groups, they can readily form these hydrogen bonds with alcohol molecules, facilitating their dissolution. In low-molecular-weight alcohols, the hydrophilic hydroxyl group dominates the molecule's properties, allowing for high solubility. However, as the molecular weight of an alcohol increases, the hydrocarbon chain attached to the hydroxyl group becomes larger. This hydrocarbon portion is hydrophobic, or "water-hating," which causes the overall solubility of the alcohol in water to decrease as the molecule grows larger.132