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Chemistry · 2026 · 4 marks
CBSE 2026 · Region 4 · Set 1 · Q29
Alcohols and Phenols are acidic in nature. Electron withdrawing groups in phenol increase its acidic strength and electron releasing groups decrease…
Alcohols and Phenols are acidic in nature. Electron withdrawing groups in phenol increase its acidic strength and electron releasing groups decrease it. Alcohols undergo nucleophilic substitution with hydrogen halides to yield alkyl halides. Dehydration of alcohols gives alkenes. On oxidation, primary alcohols yield aldehydes with mild oxidising agents and carboxylic acids with strong oxidising agents, while secondary alcohols yield ketones. Tertiary alcohols are resistant to oxidation. The presence of - OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect. Answer the following questions :
(a)
Write the mechanism of acid dehydration of ethanol to yield ethene.
(b)(i)
Why are tertiary alcohols resistant to oxidation ?
OR
(b)
(ii)
Write the structure of the major product expected from the dinitration of $\displaystyle 3$-methylphenol.
(c)
Why is ortho-nitrophenol more acidic than ortho-methoxyphenol ?
Marking-scheme solution
(a)
Step $\displaystyle 1$: Formation of protonated alcohol
Step $\displaystyle 2$: Formation of carbocation
Step $\displaystyle 3$: Deprotonation
(b)(i)
Due to the absence of α – hydrogen atom
OR
(b)
(ii)
(c)
Because of electron withdrawing nature of -NO2 group which increases the
stability of phenoxide ion whereas methoxy is electron-donating group and decreases
the stability of phenoxide ion.
All Alcohols, Phenols and Ethers questions2026 question paperNCERT solutions: Alcohols, Phenols and EthersPractice Alcohols, Phenols and Ethers →
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.