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CBSE Class 12 Chemistry 2018 Solved Paper

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Question : 9 of 26
Marks: +1, -0
How do you convert the following ?
(a) Ethanal to Propanone
(b) Toluene to Benzoic acid
OR
Account for the following:
(a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction.
(b) pKa\mathrm{p}K_{\mathrm{a}} value of 4-nitrobenzoic acid is lower than that of benzoic acid.
Solution:  
(a) CH3CHO→(ii)  H2O/H+(i)  CH3MgBr  , Dryether\mathrm{CH}_3\mathrm{CHO} \xrightarrow[\text{(ii)}\;\mathrm{H}_2\mathrm{O}/\mathrm{H}^+]{\text{(i)}\;\mathrm{CH}_3\mathrm{MgBr}\;\text{, Dryether}} CH3CH(OH)CH3CrO→3\overset{\mathrm{CrO}\rightarrow_3}{\mathrm{CH}_3\mathrm{CH}(\mathrm{OH})\mathrm{CH}_3} CH3COCH3\mathrm{CH}_3\mathrm{COCH}_3
OR
(a) because the carboxyl group is deactivating and the catalyst aluminium chloride (Lewis acid) gets bonded to the carboxyl group
(b) Nitro group is an electron withdrawing group (-I effect) so it stabilises the carboxylate anion and strengthens the acid/ due to the presence of an electron withdrawing nitro group (-I effect).
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