CBSE 2023 · Region 4 · Set 1 · Q26 · 3 marks
(i)Write hydroboration-oxidation reaction with an example.(ii)Write the products of the following reaction :
(iii)Why is p-nitrophenol more acidic than phenol ?(i)What happens when phenol reacts with(1)Conc. $\displaystyle \mathrm{HNO}_{3}$, and(2)$\displaystyle \mathrm{CHCl}_{3}$ in presence of aqueous NaOH followed by acidification? Write equations only.(ii)Why does the reaction of $\displaystyle \mathrm{CH}_{3} \mathrm{ONa}$ with $\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{Br}$ give $\displaystyle 2$-methylpropene and not $\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{OCH}_{3}$ ?
(i)
Write hydroboration-oxidation reaction with an example.
(ii)
Write the products of the following reaction :
(iii)
Why is p-nitrophenol more acidic than phenol ?
(i)
What happens when phenol reacts with
(1)
Conc. $\displaystyle \mathrm{HNO}_{3}$, and
(2)
$\displaystyle \mathrm{CHCl}_{3}$ in presence of aqueous NaOH followed by acidification? Write equations only.
(ii)
Why does the reaction of $\displaystyle \mathrm{CH}_{3} \mathrm{ONa}$ with $\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{Br}$ give $\displaystyle 2$-methylpropene and not $\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{OCH}_{3}$ ?
Marking-scheme solution
(i)
(ii)
(iii)
Because of electron-withdrawing nature or -I effect of \(\displaystyle -\mathrm{NO}_{2}\) group / p-nitrophenoxide ion is more stable than phenoxide ion / due to more effective delocalization of negative charge in p-nitrophenoxide ion.
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CBSE Class 12 Chemistry past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.