Question:

Among the compounds A and B with molecular formula \(\mathrm{C_9H_{18}O_3}\), A is having higher boiling point the B. The possible structures of A and B are :

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Check the molecular formula of each option first, then pick the pair in which A can hydrogen-bond strongly (three OH groups) and B cannot (three ether groups).
Updated On: Nov 5, 2026
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The Correct Option is D

Solution and Explanation

Option (1): A = 1,3,5-trimethoxycyclohexane, \(\mathrm{C_9H_{18}O_3}\); but B = 3,5-bis(hydroxymethyl)cyclohexanol has only 8 carbons (\(\mathrm{C_8H_{16}O_3}\)), so it does not fit the formula.
Option (2): A is the ether (no O-H) and B is the triol (\(\mathrm{C_9H_{18}O_3}\)); A would have the lower boiling point, contradicting the condition.
Option (3): both A and B are triols (3 OH each) with formula \(\mathrm{C_9H_{18}O_3}\); both hydrogen-bond to a similar extent, so there is no clear reason for A to boil much higher than B.
Option (4): A = 1,3,5-tris(hydroxymethyl)cyclohexane (three OH groups, extensive intermolecular H-bonding) and B = 1,3,5-trimethoxycyclohexane (no O-H, no H-bonding); both are \(\mathrm{C_9H_{18}O_3}\) and A boils much higher than B.
Answer: (4) A = 1,3,5-tris(hydroxymethyl)cyclohexane, B = 1,3,5-trimethoxycyclohexane
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