Unit 11 Alcohols, Phenols And Ethers (Intext Questions-4)
Intext Questions
11.6 Give structures of the products you would expect when each of the following alcohol reacts with (a) ${HCl}-{ZnCl_2}$ (b) ${HBr}$ and (c) ${SOCl_2}$.
(i) Butan-1-ol
(ii) 2-Methylbutan-2-ol
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Answer
(a)
(i) $\underset{\text{Butan-1-ol}}{{CH_3}-{CH_2}-{CH_2}-{CH_2}-{OH}} \xrightarrow{{HCl} - {ZnCl_2}} \text { No reaction }$
Primary alcohols do not react appreciably with Lucas’ reagent $\left({HCl}-{ZnCl_2}\right)$ at room temperature.
(ii)
Tertiary alcohols react immediately with Lucas’ reagent
(b)
(i) $\underset{\text{Butan-1-ol}}{{CH_3} {CH_2} {CH_2} {CH_2} {OH}}+{HBr} \xrightarrow{{-H_2O}}\underset{\text{1-Bromobutane}}{{CH_3} {CH_2} {CH_2} {CH_2} {Br}}$
(ii)
(c)
(i) $\underset{\text{Butan-1-ol}}{{CH_3} {CH_2} {CH_2} {CH_2} {OH}}+{SOCl_2} \longrightarrow \underset{\text{1-chlorobutane}}{{CH_3} {CH_2} {CH_2} {CH_2} {Cl}}+{SO_2}+{HCl}$
(ii)
11.7 Predict the major product of acid catalysed dehydration of
(i) 1-methylcyclohexanol and
(ii) butan-1-ol
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Answer
(i)
(ii) A Mixture of but-1-ene and but-2-ene. But-2-ene is the major product formed due to rearrangement to give secondary carbocation.
$\underset{\text{Butan-1-ol}}{{CH_3} {CH_2} {CH_2} {CH_2} {OH}} \xrightarrow[{H^+}]{\text { Dehydration }} \underset{\substack{\text{But-2-ene }\\ \text{(Major product)}}}{{CH_3} {CH}={CHCH_3}}+\underset{\substack{\text{But-1-ene }\\ \text{(Minor product)}}}{{CH_3} {CH_2}{CH=CH_2}}$
11.8 Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.
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Answer
Resonance structure of the phenoxide ion :
Resonance structures of $p$-nitrophenoxide ion :
Resonance structures of o-nitrophenoxide ion :
It can be observed that the presence of nitro groups increases the stability of phenoxide ion.
11.9 Write the equations involved in the following reactions:
(i) Reimer - Tiemann reaction
(ii) Kolbe’s reaction
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Answer
(i) Reimer-Tiemann reaction
(ii) Kolbe’s reaction
BETA
