JEE Main 2023 — Alcohols Phenols And Ethers Question with Solution
From: JEE Main 2023 (Online) 8th April Morning Shift
Question
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Butan -1- ol has higher boiling point than ethoxyethane.
Reason R: Extensive hydrogen bonding leads to stronger association of molecules.
In the light of the above statements, choose the correct answer from the options given below:
Choose an option
Show full solutionCorrect option: C
Step-by-step explanation
The boiling point of a substance is dependent on the strength of the intermolecular forces between its molecules. Stronger intermolecular forces require more energy to overcome, thus resulting in a higher boiling point.
In the case of butan-1-ol and ethoxyethane (diethyl ether), they are both composed of similar numbers of similar atoms, but the type of intermolecular force between the molecules differs due to their functional groups.
Butan-1-ol is an alcohol and has a -OH group, which allows for hydrogen bonding, a strong type of dipole-dipole interaction. This happens when the hydrogen atom in a polar bond (especially -OH, -NH, -HF) is attracted to some electronegative atom (like O, N, or F) in another molecule. Because of this, butan-1-ol molecules "stick together" more strongly, requiring more heat energy to separate them and thus exhibiting a higher boiling point.
On the other hand, ethoxyethane, being an ether, does not have the ability to form hydrogen bonds since it lacks the -OH group. The primary intermolecular forces in ethers are relatively weaker van der Waals forces. Therefore, it requires less heat energy to break these forces, resulting in a lower boiling point compared to butan-1-ol.
So, both A and R are true and R is indeed the correct explanation for A.
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This is a previous-year question from JEE Main 2023, covering the Alcohols Phenols And Ethers chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.