Explain, why `o`-hydroxybenzaldehyde is a liquid at room temperature while `p`-hydroxybenzaldehyde is a high melting solid?

Explanation

Due to intramolecular H-bonding (chelation), o-hydroxybenzaldehyde exists as discrete

molecules while due to inetermolecular H-bonding, p-hydroxybenzaldehyde exists as associated molecules. To break these intermolecular H-bonds, a large amount of energy is needed. consequently, p-hydroxy-benzaldehyde has a much higher m.p. and b.p. than that of o-hydroxybezaldehyde. as a result, o-hydroxy-benzaldehyde is a liquid at room temperature while p-hydroxybanzaldehyde is a high melting solid.