See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: Boiling points of organic compounds depend on intermolecular forces — hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Compounds capable of hydrogen bonding (alcohols, diols) have significantly higher boiling points than those that cannot (ethers). Step 1: Identify each compound. (a) A branched or unsaturated primary alcohol (monohydric, ~C5) — can form hydrogen bonds, relatively high boiling point. (b) Pentan-1-ol — a straight-chain primary alcohol (monohydric, C5) — can form hydrogen bonds, higher boiling point than branched isomers due to greater surface area. (c) Diethyl ether (ethoxyethane, CH3CH2OCH2CH3) — an ether with no O-H bond, cannot act as hydrogen bond donor; only has weak dipole-dipole and van der Waals forces. BP = 34.6°C. (d) A diol (two OH groups) — can form extensive hydrogen bonding both as donor and acceptor; much higher boiling point than monohydric alcohols. Step 2: Compare boiling points. - Diols (option d) have the highest boiling points due to two OH groups enabling extensive H-bonding. - Monohydric alcohols (options a and b) have intermediate boiling points; straight-chain (b) is slightly higher than branched (a) due to more surface contact. - Ethers (option c) have the lowest boiling points among these because they lack O-H bonds and therefore cannot donate hydrogen bonds, resulting in much weaker intermolecular forces. Step 3: Why other options fail. - (a) and (b) are alcohols with H-bonding capability — higher BP than ether. - (d) is a diol with two OH groups — highest BP of all four. - (c) diethyl ether has BP ~34.6°C, far lower than any alcohol listed. Therefore, the correct answer is C.