Class 12
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Chemistry
Alcohols, Phenols and Ethers
NCERT Solutions
NCERT Solutions
Alcohols, Phenols and Ethers
33 Solutions
Q1
Exercises
Write IUPAC names of the following compounds:
(i)
C
H
3
−
C
H
(
C
H
3
)
−
C
H
(
O
H
)
−
C
(
C
H
3
)
3
CH_3-CH(CH_3)-CH(OH)-C(CH_3)_3
C
H
3
−
C
H
(
C
H
3
)
−
C
H
(
O
H
)
−
C
(
C
H
3
)
3
(ii)
C
H
3
C
H
2
C
H
(
C
H
2
C
H
3
)
C
H
(
O
H
)
C
H
(
C
H
3
)
C
H
2
O
H
CH_3CH_2CH(CH_2CH_3)CH(OH)CH(CH_3)CH_2OH
C
H
3
C
H
2
C
H
(
C
H
2
C
H
3
)
C
H
(
O
H
)
C
H
(
C
H
3
)
C
H
2
O
H
(iii)
C
H
3
C
H
(
O
H
)
C
H
(
O
H
)
C
H
3
CH_3CH(OH)CH(OH)CH_3
C
H
3
C
H
(
O
H
)
C
H
(
O
H
)
C
H
3
(iv)
H
O
C
H
2
C
H
(
O
H
)
C
H
2
O
H
HOCH_2CH(OH)CH_2OH
H
OC
H
2
C
H
(
O
H
)
C
H
2
O
H
(v)
o-Cresol (structure with -OH and -CH3 on adjacent carbons of a benzene ring)
(vi)
p-Cresol (structure with -OH and -CH3 on opposite carbons of a benzene ring)
(vii)
2,5-Dimethylphenol
(viii)
2,6-Dimethylphenol
(ix)
C
H
3
−
O
−
C
H
2
−
C
H
(
C
H
3
)
2
CH_3-O-CH_2-CH(CH_3)_2
C
H
3
−
O
−
C
H
2
−
C
H
(
C
H
3
)
2
(x)
C
6
H
5
−
O
−
C
2
H
5
C_6H_5-O-C_2H_5
C
6
H
5
−
O
−
C
2
H
5
(xi)
C
6
H
5
−
O
−
C
7
H
15
(
n
−
)
C_6H_5-O-C_7H_{15}(n-)
C
6
H
5
−
O
−
C
7
H
15
(
n
−
)
(xii)
C
H
3
C
H
2
−
O
−
C
H
(
C
H
3
)
C
H
2
C
H
3
CH_3CH_2-O-CH(CH_3)CH_2CH_3
C
H
3
C
H
2
−
O
−
C
H
(
C
H
3
)
C
H
2
C
H
3
Q2
Exercises
Write structures of the compounds whose IUPAC names are as follows:
(i)
2-Methylbutan-2-ol
(ii)
1-Phenylpropan-2-ol
(iii)
3,5-Dimethylhexane-1,3,5-triol
(iv)
2,3 - Diethylphenol
(v)
1 - Ethoxypropane
(vi)
2-Ethoxy-3-methylpentane
(vii)
Cyclohexylmethanol
(viii)
3-Cyclohexylpentan-3-ol
(ix)
Cyclopent-3-en-1-ol
(x)
4-Chloro-3-ethylbutan-1-ol.
Q3
Exercises
(i)
Draw the structures of all isomeric alcohols of molecular formula
C
5
H
12
O
C_5H_{12}O
C
5
H
12
O
and give their IUPAC names.
(ii)
Classify the isomers of alcohols in question 7.3 (i) as primary, secondary and tertiary alcohols.
Q4
Exercises
Explain why propanol has higher boiling point than that of the hydrocarbon, butane?
Q5
Exercises
Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
Q6
Exercises
What is meant by hydroboration-oxidation reaction? Illustrate it with an example.
Q7
Exercises
Give the structures and IUPAC names of monohydric phenols of molecular formula,
C
7
H
8
O
C_7H_8O
C
7
H
8
O
.
Q8
Exercises
While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.
Q9
Exercises
Give the equations of reactions for the preparation of phenol from cumene.
Q10
Exercises
Write chemical reaction for the preparation of phenol from chlorobenzene.
Q11
Exercises
Write the mechanism of hydration of ethene to yield ethanol.
Q12
Exercises
You are given benzene, conc.
H
2
S
O
4
H_2SO_4
H
2
S
O
4
and NaOH. Write the equations for the preparation of phenol using these reagents.
Q13
Exercises
Show how will you synthesise:
(i)
1-phenylethanol from a suitable alkene.
(ii)
cyclohexylmethanol using an alkyl halide by an
S
N
2
S_N2
S
N
2
reaction.
(iii)
pentan-1-ol using a suitable alkyl halide?
Q14
Exercises
Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.
Q15
Exercises
Explain why is ortho nitrophenol more acidic than ortho methoxyphenol ?
Q16
Exercises
Explain how does the -OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?
Q17
Exercises
Give equations of the following reactions:
(i)
Oxidation of propan-1-ol with alkaline
K
M
n
O
4
KMnO_4
K
M
n
O
4
solution.
(ii)
Bromine in
C
S
2
CS_2
C
S
2
with phenol.
(iii)
Dilute
H
N
O
3
HNO_3
H
N
O
3
with phenol.
(iv)
Treating phenol wih chloroform in presence of aqueous NaOH.
Q18
Exercises
Explain the following with an example.
(i)
Kolbe's reaction.
(ii)
Reimer-Tiemann reaction.
(iii)
Williamson ether synthesis.
(iv)
Unsymmetrical ether.
Q19
Exercises
Write the mechanism of acid dehydration of ethanol to yield ethene.
Q20
Exercises
How are the following conversions carried out?
(i)
Propene → Propan-2-ol.
(ii)
Benzyl chloride → Benzyl alcohol.
(iii)
Ethyl magnesium chloride → Propan-1-ol.
(iv)
Methyl magnesium bromide → 2-Methylpropan-2-ol.
Q21
Exercises
Name the reagents used in the following reactions:
(i)
Oxidation of a primary alcohol to carboxylic acid.
(ii)
Oxidation of a primary alcohol to aldehyde.
(iii)
Bromination of phenol to 2,4,6-tribromophenol.
(iv)
Benzyl alcohol to benzoic acid.
(v)
Dehydration of propan-2-ol to propene.
(vi)
Butan-2-one to butan-2-ol.
Q22
Exercises
Give reason for the higher boiling point of ethanol in comparison to methoxymethane.
Q23
Exercises
Give IUPAC names of the following ethers:
(i)
C
H
3
C
H
2
−
O
−
C
H
2
−
C
H
(
C
H
3
)
2
CH_3CH_2-O-CH_2-CH(CH_3)_2
C
H
3
C
H
2
−
O
−
C
H
2
−
C
H
(
C
H
3
)
2
(ii)
C
H
3
O
C
H
2
C
H
2
C
l
CH_3OCH_2CH_2Cl
C
H
3
OC
H
2
C
H
2
Cl
(iii)
O
2
N
−
C
6
H
4
−
O
C
H
3
(
p
)
O_2N-C_6H_4-OCH_3(p)
O
2
N
−
C
6
H
4
−
OC
H
3
(
p
)
(iv)
C
H
3
C
H
2
C
H
2
O
C
H
3
CH_3CH_2CH_2OCH_3
C
H
3
C
H
2
C
H
2
OC
H
3
(v)
Structure with an ethoxy group and a 1,1-dimethyl group on a cyclohexane ring, with ethoxy at position 2.
(vi)
C
2
H
5
−
O
−
C
6
H
5
C_2H_5-O-C_6H_5
C
2
H
5
−
O
−
C
6
H
5
Q24
Exercises
Write the names of reagents and equations for the preparation of the following ethers by Williamson's synthesis:
(i)
1-Propoxypropane
(ii)
Ethoxybenzene
(iii)
2-Methoxy-2-methylpropane
(iv)
1-Methoxyethane
Q25
Exercises
Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.
Q26
Exercises
How is 1-propoxypropane synthesised from propan-1-ol? Write mechanism of this reaction.
Q27
Exercises
Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.
Q28
Exercises
Write the equation of the reaction of hydrogen iodide with:
(i)
1-propoxypropane
(ii)
methoxybenzene
(iii)
benzyl ethyl ether.
Q29
Exercises
Explain the fact that in aryl alkyl ethers (i) the alkoxy group activates the benzene ring towards electrophilic substitution and (ii) it directs the incoming substituents to ortho and para positions in benzene ring.
Q30
Exercises
Write the mechanism of the reaction of HI with methoxymethane.
Q31
Exercises
Write equations of the following reactions:
(i)
Friedel-Crafts reaction - alkylation of anisole.
(ii)
Nitration of anisole.
(iii)
Bromination of anisole in ethanoic acid medium.
(iv)
Friedel-Craft's acetylation of anisole.
Q32
Exercises
Show how would you synthesise the following alcohols from appropriate alkenes?
(i)
1-Methylcyclohexanol
(ii)
4-Methylheptan-4-ol
(iii)
Pentan-2-ol
(iv)
3-Cyclohexylpentan-3-ol
Q33
Exercises
When 3-methylbutan-2-ol is treated with HBr, the following reaction takes place:
C
H
3
−
C
H
(
O
H
)
−
C
H
(
C
H
3
)
2
+
H
B
r
→
C
H
3
−
C
(
B
r
)
(
C
H
3
)
−
C
H
2
−
C
H
3
CH_3-CH(OH)-CH(CH_3)_2 + HBr \rightarrow CH_3-C(Br)(CH_3)-CH_2-CH_3
C
H
3
−
C
H
(
O
H
)
−
C
H
(
C
H
3
)
2
+
H
B
r
→
C
H
3
−
C
(
B
r
)
(
C
H
3
)
−
C
H
2
−
C
H
3
Give a mechanism for this reaction. (Hint : The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom.)
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