Which amongst the following will be most readily dehydrated under acidic conditions ? 1. skeletal structure (1) bearing NO ₂ and OH (see figure) 2. skeletal structure (2) bearing NO ₂ , OH, CH ₃ and H (see figure) 3. skeletal structure (3) bearing two OH, H ₃ C and H (see figure) 4. skeletal structure (4) bearing NO ₂ , H, two OH (see figure)

Answer: 3. skeletal structure (3) bearing two OH, H ₃ C and H (see figure) Key idea: Acid-catalysed dehydration of an alcohol goes through a carbocation (or a carbocation-like transition state), so groups that pull electrons away make it harder. Option 4: -NO₂ sits on the carbon next to the C-OH carbon, so its strong -I effect is felt most. It dehydrates least readily. Option 2: -NO₂ is one carbon farther (on C-4, with OH on C-2); the effect is still strong. Option 1: -NO₂ is three carbons from the C-OH carbon, so it is weak, but it is still an electron-withdrawing group. Option 3 (pentane-2,4-diol) has no nitro group, only a second OH, and it is the one the official key picks. Answer: option 3. The comparison between options 1 and 3 is qualitative; the question gives no further data.

Topic: Alcohols: identification of 1/2/3 alcohols, dehydration mechanism· Organic Compounds Containing Oxygen

Which amongst the following will be most readily dehydrated under acidic conditions ?

four skeletal structures (options 1-4)

1. skeletal structure (1) bearing NO\(_2\) and OH (see figure)

2. skeletal structure (2) bearing NO\(_2\), OH, CH\(_3\) and H (see figure)

3. skeletal structure (3) bearing two OH, H\(_3\)C and H (see figure)

4. skeletal structure (4) bearing NO\(_2\), H, two OH (see figure)

Doubtly Asked 30 Oct 2026 NEET UG 2023 Practice test neet Save WhatsApp Report

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Answer: 3. skeletal structure (3) bearing two OH, H\(_3\)C and H (see figure)

Key idea: Acid-catalysed dehydration of an alcohol goes through a carbocation (or a carbocation-like transition state), so groups that pull electrons away make it harder.

Option 4: \(\mathrm{-NO_2}\) sits on the carbon next to the C-OH carbon, so its strong \(-I\) effect is felt most. It dehydrates least readily.
Option 2: \(\mathrm{-NO_2}\) is one carbon farther (on C-4, with OH on C-2); the effect is still strong.
Option 1: \(\mathrm{-NO_2}\) is three carbons from the C-OH carbon, so it is weak, but it is still an electron-withdrawing group.
Option 3 (pentane-2,4-diol) has no nitro group, only a second OH, and it is the one the official key picks.

Answer: option 3. The comparison between options 1 and 3 is qualitative; the question gives no further data.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Which amongst the following will be most readily dehydrated under acidic conditions ?

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