NCERT Solutions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers

NCERT Solutions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers - This article covers NCERT Class 12 Chemistry solutions chapter 11. You are going to study the Chemistry of three classes of compounds which are alcohols, phenols and ethers and also this chapter will discuss the reactions involved in the preparation of alcohols, phenols and ethers.

Alcohols are formed when a hydrogen atom in an aliphatic hydrocarbon is replaced by -OH group and Phenols are formed when a hydrogen atom in an aromatic hydrocarbon is replaced by –OH group while Ethers are formed by the substitution of an H-atom in a hydrocarbon by an alkoxy(R-O) or by an aryloxy(Ar-O) group.The NCERT solutions for Class 12 Chemistry chapter 11 Alcohols, Phenols and Ethers are prepared by Chemistry subject experts. These NCERT solutions help students in their preparation for the CBSE Board exam and in competitive exams like JEE Mains, NEET etc.

Also Read| Alcohols Phenols and Ethers Class 12 Notes

NCERT solutions for Class 12 Chemistry chapter 11 Alcohols, Phenols and Ethers start with the IUPAC nomenclature of alcohols, phenols and ethers followed by the topics:- reactions involved in the preparation of alcohols from aldehydes, ketones, alkenes and carboxylic acids and discuss reactions involved in the preparation of phenols from benzene sulphonic acids, haloarenes, cumene and diazonium salts. Alcohols Phenols and Ethers Class 12 also discuss reactions involved in the preparation of ethers from alcohols and alkyl halides. Scroll down to know more details about the NCERT solutions for Class 12 Chemistry Chapter 11 PDF download.

Find NCERT Solutions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Below:

Solutions to In-Text Questions Ex 11.1 to 11.12

Question 11. 1 (1) Classify the following as primary, secondary and tertiary alcohols:

int1

Answer :

To classify we look at the OH bonded carbon.

Here, only 1 carbon is attached to it, hence it is primary alcohol .

Question 11.1 (2) Classify the following as primary, secondary and tertiary alcohols:

int2

Answer :

To classify we look at the OH bonded carbon.

Here, only 1 carbon is attached to it, hence it is primary alcohol.

Question 11.1 (3) Classify the following as primary, secondary and tertiary alcohols:

$CH_3 -CH_2- CH_2 -OH$

Answer :

To classify we look at the OH bonded carbon.

Here, only 1 carbon is attached to it, hence it is primary alcohol.

Question 11.1 (4) Classify the following as primary, secondary and tertiary alcohols:

int4

Answer :

To classify we look at the OH bonded carbon.

Here, 2 carbons are attached to it, hence it is secondary alcohol.

Question 11.1 (5) Classify the following as primary, secondary and tertiary alcohols:

int5

Answer :

To classify we look at the OH bonded carbon.

Here, 2 carbons are attached to it, hence it is secondary alcohol.

Question 11.1 (6) Classify the following as primary, secondary and tertiary alcohols :

1649963634534

Answer:

To classify we look at the OH bonded carbon.

Here, 3 carbons are attached to it, hence it is tertiary alcohol.

Question 11.2 Identify allylic alcohols in the above examples.

Answer :

The alcohols (ii) and (vi) are allylic alcohols. Because -C=C-C-OH is the skeleton of allylic alcohol.

Question 11.3 (1) Name the following compounds according to IUPAC system.

1649963673264

Answer :

3-Chloromethyl-2-isopropylpentan-1-ol

Question 11.3 (2) Name the following compounds according to IUPAC system.

1649963717497

Answer :

2, 5-Dimethylhexane-1, 3-diol

Question 11.3 (3) Name the following compounds according to IUPAC system.

1649963822470

Answer :

3-Bromocyclohexanol

Question 11.3 (4) Name the following compounds according to IUPAC system.

1649963863346

Answer :

Hex-1-en-3-ol

Question 11.3 (5) Name the following compounds according to IUPAC system.

1649963909613

Answer :

2-Bromo-3-methylbut-2-en-1-ol

Question 11.4 (1) Show how are the following alcohols prepared by the reaction of a suitable Grignard reagent on methanal ?

1649963974883

Answer :

The reaction of a suitable Grignard reagent on the methanal is mentioned below:

1649963954035

Question 11.4 (2) Show how are the following alcohols prepared by the reaction of a suitable
Grignard reagent on methanal ?

1649964024243

Answer :

1649964043498

Question 11.5 (1) Write structures of the products of the following reactions: gwear

Answer :

1649964112055

Question 11.5 (2) Write structures of the products of the following reactions: efwefew

1649964371846

Answer :

Product of the given reaction is-

1649964168123

Question 11.5 (3) Write structures of the products of the following reactions: sdgsfwe

Answer : 1649964224157

Product of the given reaction is

1649964252232

Question 11.6 (1) Give structures of the products you would expect when each of the following alcohol reacts with

(a) $HCL- ZnCl_2$ with Butan-1-ol

Answer :

Primary alcohols do no react with Lucas’ reagent.

Hence no reaction.

Question 11.6 (2) Give structures of the products you would expect when each of the following alcohol reacts with $HCl - ZnCl_2$ with 2-Methylbutan-2-ol

Answer :

Reaction of $HCl - ZnCl_2$ with 2-Methylbutan-2-ol

1649964290479

Question 11.6 (3) Give structures of the products you would expect when each of the following alcohol reacts with HBr with Butan-1-ol

Answer :

Reaction of HBr with Butan-1-ol

1649964332727

Question 11.6 (4) Give structures of the products you would expect when each of the following alcohol reacts with HBr with 2-Methylbutan-2-ol

Answer :

Reaction of HBr with 2-Methylbutan-2-ol

1649964449101

Question 11.6 (5) Give structures of the products you would expect when each of the following alcohol reacts with $SOCl_2$ with Butan-1-ol

Answer :

Reaction of $SOCl_2$ with Butan-1-ol

1649964487196

Question 11.6 (6) Give structures of the products you would expect when each of the following alcohol reacts with $SoCl_2$ with 2-Methylbutan-2-ol

Answer :

Reaction of $SoCl_2$ with 2-Methylbutan-2-ol

1649964525510

Question 11.7(1) Predict the major product of acid catalysed dehydration of 1-methylcyclohexanol

Answer :

Dehydration of 1-methylcyclohexanol

1649964563324

1-Methylcyclohexene is the major product.

Question 11.7 (2) Predict the major product of acid catalysed dehydration of butan-1-ol

Answer :

Dehydration of butan-1-ol

1649964596061

But-2-ene is the major product.

Question 11.8 Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.

Answer :

Resonance structure of ortho-nitrophenol

1649964631687

Resonance structure of para-nitrophenol

1649964652729

Question 11.9 (1) Write the equations involved in the following reactions: Reimer - Tiemann reaction

Answer :

Reimer - Tiemann reaction

1649964703424

Question 11.9 (2) Write the equations involved in the following reactions: Kolbe’s reaction

Answer :

Kolbe’s reaction

1649964746071

Question 11.10 Write the reactions of Williamson synthesis of 2-ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.

Answer :

1.Reaction of ethanol with hydrogen bromide.

1649964791076

2. Reaction of 3-methylpentan-2-ol with sodium

1649964898068

3. Reaction of product formed in 1st and reaction with the product formed in the 2nd reaction.

1649964914852

Question 11.11 Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why?

1649965008877

Answer :

(ii) is appropriate because $CH_3Br$ is nucleophile whereas $CH_3ONa$ is also a strong base. So elimination will be dominating in (i).

Question 11.12 (1) Predict the products of the following reactions:

$CH_3 -CH_2 -CH_2 -O - CH_3 +HBr$

Answer :

Reaction is

1649965070178

Question 11.12 (2) Predict the products of the following reactions:

1649965128401

Answer :

The reaction between ethoxybenzene and HBr is

1649965110827

Question 11.12 (3) Predict the products of the following reactions:

1649965169971

Answer :

Reaction between ethoxybenzene and $Conc. \:H_{2}SO_{4} \:+\:conc. HNO_{3}$

1649965188865

Question 11.12 (4) Predict the products of the following reactions:

1649965226084

Answer :

Reaction between ter - butyl ethyl ether and HI

1649965242940

NCERT Solutions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers - Exercise Questions

Question 11.1 (1) Write IUPAC names of the following compounds:

1649965274378

Answer :

IUPAC name of the given compound is 2,2,4-Trimethylpentan-3-ol

Question 11.1 (2) Write IUPAC names of the following compounds:

1649965319080

Answer :

IUPAC name of the given compound is 5-Ethylheptane-2,4-diol

Question 11.1 (3) Write IUPAC names of the following compounds:

1649965354978

Answer :

IUPAC name of the given compound is Butane-2,3-diol

Question 11.1 (4) Write IUPAC names of the following compounds:

1649965421081

Answer :

IUPAC name of the given compound is Propane-1,2,3-triol

Question 11.1 (5) Write IUPAC names of the following compounds:

1649965465500

Answer :

IUPAC name of the given compound is 2-Methylphenol

Question 11.1 (6) Write IUPAC names of the following compounds:

1649965524003

Answer :

IUPAC name of the given compound is 4-Methylphenol

Note : Also called p-cresol

Question 11.1 (7) Write IUPAC names of the following compounds:

1649965563584

Answer :

IUPAC name of the given compound is 2,5-Dimethylphenol

Question 11.1 (8) Write IUPAC names of the following compounds:

1594976548377 1594976545954

Answer :

IUPAC name of the given compound is 2,6-Dimethylphenol

Question 11.1 (9) Write IUPAC names of the following compounds:

1649965645747

Answer :

IUPAC name of the given compound is 1-Methoxy-2-methylpropane

Question 11.1 (10) Write IUPAC names of the following compounds:

1649965690874

Answer :

IUPAC name of the given compound is Ethoxybenzene

Question 11.1 (11) Write IUPAC names of the following compounds:

1649965735782

Answer :

IUPAC name of the given compound is 1-Phenoxyheptane

Question 11.1 (12) Write IUPAC names of the following compounds:

1594976564404 1594976562819

Answer :

IUPAC name of the given compound is 2-Ethoxybutane

Question 11.2 Write structures of the compounds whose IUPAC names are as follows:
(i) 2-Methylbutan-2-ol

Answer :

Structure of 2-Methylbutan-2-ol

1649965777770

Question 11.2 Write structures of the compounds whose IUPAC names are as follows: (ii) 1-Phenylpropan-2-ol

Answer :

Structure of 1-Phenylpropan-2-ol

1649965829440

Question 11.2(iii) Write structures of the compounds whose IUPAC names are as follows: (iii) 3,5-Dimethylhexane –1, 3, 5-triol

Answer :

structure of 3,5-Dimethylhexane –1, 3, 5-triol

1649965957466

Question 11.2(iv) Write structures of the compounds whose IUPAC names are as follows: (iv) 2,3 – Diethylphenol

Answer :

structure of 2,3 – Diethylphenol

1649965990130

Question 11.2(v) Write structures of the compounds whose IUPAC names are as follows:
(v) 1 – Ethoxypropane

Answer :

structure of 1 – Ethoxypropane

1649966018689

Question 11.2(vi) Write structures of the compounds whose IUPAC names are as follows:
(vi) 2-Ethoxy-3-methylpentane

Answer :

structure of 2-Ethoxy-3-methylpentane

1649966071934

Question 11.2(vii) Write structures of the compounds whose IUPAC names are as follows:
(vii) Cyclohexylmethanol

Answer :

Structure of Cyclohexylmethanol

1649966113638

Question 11.2(viii) Write structures of the compounds whose IUPAC names are as follows:
(viii) 3-Cyclohexylpentan-3-ol

Answer :

The structure of 3-Cyclohexylpentan-3-ol is as follows:

1649966143832

Question 11.2(ix) Write structures of the compounds whose IUPAC names are as follows:
(ix) Cyclopent-3-en-1-ol

Answer :

structure of Cyclopent-3-en-1-ol

1649966178429

Question 11.2(x) Write structures of the compounds whose IUPAC names are as follows:
(x) 4-Chloro-3-ethylbutan-1-ol.

Answer :

structure of 4-Chloro-3-ethylbutan-1-ol

1649966222407

Question 11. 3 (i) Draw the structures of all isomeric alcohols of molecular formula $C_5 H_{12}O$
and give their IUPAC names.

Answer :

The structures of all isomeric alcohols of C ₅ H ₁₂ O are given below:

	Pentan-1-ol
	Pentan-2-ol
	Pentan-3-ol
	3-Methylbutan-1-ol
	3-Methylbutan-1-ol
	2,2-Dimethylpropan-1-ol
	3-Methylbutan-2-ol
	2-Methylbutan-2-ol

Question 11. 3 (ii) Classify the isomers of alcohols in question 11.3 (i) as primary, secondary and tertiary alcohols.

Answer :

Primary Alcohol: Pentan-1-ol; 2-Methylbutan-1-ol; 3-Methylbutan-1-ol; 2,2-Dimethylpropan-1-ol

Secondary Alcohol: Pentan-2-ol; 3-Methylbutan-2-ol; Pentan-3-ol

Tertiary Alcohol: 2-Methylbutan-2-ol

Question 11.4 Explain why propanol has higher boiling point than that of the hydrocarbon, butane?

Answer :

Propanol forms intermolecular H-bonds because of the presence of -OH group while butane cannot. To break these bonds, extra energy will be required. This causes a higher boiling point for propanol as compared to butane.

Question 11.5 Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.

Answer :

Alcohols form hydrogen bonds with water due to the presence of –OH group whereas hydrocarbons cannot. Due to this inter molecular hydrogen bonding, alcohols are more soluble in water.

Question 11.6 What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

Answer :

Hydroboration-oxidation reaction also called HBO reaction is the addition of borane followed by oxidation to produce alcohol.

Eg: Hydroboration-oxidation reaction of propene. In this reaction, propene reacts with diborane (BH ₃ ) ₂ to form trialkyl borane. This addition product is oxidized by hydrogen peroxide in the presence of aqueous sodium hydroxide to form propan-1-ol.

Question 11.7 Give the structures and IUPAC names of monohydric phenols of molecular formula, $C_7 H_8 O$ .

Answer :

The structures and IUPAC names of monohydric phenols of molecular formula, $C_7 H_8 O$ .

Phenol: $C_6 H_5 OH$

$C_7 H_8 O \rightarrow (C_6 H_5 OH)(C H_2)$

1649966313305

Question 11.8 While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.

Answer :

Due to inter-molecular H bonding in para-nitrophenol, it gets tightly bonded with water. But ortho nitrophenol has intra-molecular H bonding and hence is steam volatile.

Question 11.9 Give the equations of reactions for the preparation of phenol from cumene.

Answer :

Cumene (isopropylbenzene) is oxidised in the presence of air to form cumene hydroperoxide. On treating with dilute acid it is converted to phenol and acetone.

1649966356497

Question 11.10 Write chemical reaction for the preparation of phenol from chlorobenzene.

Answer :

Chlorobenzene, when fused with NaOH, produces sodium phenoxide which on acidification produces Phenol.

1649966463015

Question 11.11 Write the mechanism of hydration of ethene to yield ethanol.

Answer :

Ethanol is yielded from ethene by acid catalysed hydration.

The mechanism:

Step 1. Protonation of alkene to form carbocation by electrophilic attack of hydronium ion.

1649966496746

Step 2. Nucleophilic attack of water on carbocation .

1649966514431

Step 3. Deprotonation to form an alcohol.

1649966531637

Question 11.12 You are given benzene, $conc. H_2SO_4$ and NaOH. Write the equations for the preparation of phenol using these reagents .

Answer :

When benzene reacts with $conc. \:H_2SO_4$ and heat it gives benzene sulphonic acid ,and after sulphonic this acid with NaOH then it gives phenol

1649966572842

Question 11.13 Show how will you synthesise:
(i) 1-phenylethanol from a suitable alkene.

Answer :

Styrene on acid catalysed hydration gives 1-phenylethanol.

1649966607271

Question 11.13 (2) Show how will you synthesise:
(ii) cyclohexylmethanol using an alkyl halide by an SN2 reaction.

Answer :

On adding NaOH to chloromethylcyclohexane, cyclohexy methanol is formed.

1649966644075

Question 11.13 Show how will you synthesise:
(iii) pentan-1-ol using a suitable alkyl halide?

Answer :

when 1-chloropentane reacts with NaOH it gives pantan-1-ol

1649966679228

Question 11.14 Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.

Answer :

1. Phenol reacts with sodium to give sodium phenoxide, liberating hydrogen gas.

1519019443005476

2. Phenol reacts with sodium hydroxide to give sodium phenoxide and water.

1519019443784771

Phenol is more acidic than ethanol. This is because phenol after losing a proton becomes phenoxide ion which is highly stable due to resonance whereas ethoxide ion does not.

Question 11.15 Explain why is ortho nitrophenol more acidic than ortho methoxyphenol ?

Answer :

Ortho-nitrophenol is more acidic than ortho- methoxyphenol . The presence of the nitro group, which is an electron withdrawing group, at the ortho position decreases the electron density in the O-H bond. Also, the o- nitrophenoxide ion formed after the loss of protons is stabile due to resonance. Hence, ortho nitrophenol is a stronger acid. Whereas the methoxy group is an electron-releasing group. Thus, it increases the electron density in the O-H bond.

Question 11.16 Explain how does the –OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?

Answer :

The -OH group is an electron-donating group (EDG). Thus, it increases the electron density in the benzene ring in the resonance structure of phenol. As a result, the benzene ring is activated towards electrophilic substitution.

Question 11.17(i) Give equations of the following reactions:
(i) Oxidation of propan-1-ol with alkaline $KMnO_4$ solution.

Answer :

Oxidation of propane-1-ol with alkaline $KMnO_4$ solution gives propanoic acid.

$\\CH_3CH_2CH_2OH \rightarrow CH_3CH_2COOH\\propane-1-ol\:\:\:\:\:\:\:\:propanoic \:acid$

Question 11.17(ii) Give equations of the following reactions:

(ii) Bromine in $CS_2$ with phenol.

Answer :

Bromine in $CS_2$ with phenol produces a mixture of o-bromo phenol and p-bromo phenol is formed.

1649966712433

Question 11.17(iii) Give equations of the following reactions:

(iii) Dilute HNO3 with phenol.

Answer :

When dilute HNO3 reacts with phenol it gives o-bromo phenol and p-bromo phenol

1649966745746

Question 11.17(iv) Give equations of the following reactions:
(iv) Treating phenol with chloroform in presence of aqueous NaOH.

Answer :

Treating phenol with chloroform in presence of aqueous NaOH.

1649966793128

This reaction is known as the Reimer-Tiemann reaction.

Question 11.18(i) Explain the following with an example.
(i) Kolbe’s reaction.

Answer :

Kolbe’s reaction: Phenol with carbon dioxide under pressure followed by treating the product with sulphuric acid produces Ortho-hydroxybenzoic acid (salicylic acid). Phenoxide ion generated is more reactive than phenol towards electrophilic aromatic substitution. Hence, it undergoes electrophilic substitution with carbon dioxide, a weak electrophile.

1649966822710

Question 11.18(ii) Explain the following with an example.
(ii) Reimer-Tiemann reaction.

Answer :

On treating phenol with chloroform in the presence of sodium hydroxide, a –CHO group is introduced at the ortho position of the benzene ring. This reaction is known as Reimer - Tiemann reaction

1649966859823

Question 11.18(iii) Explain the following with an example. (iii) Williamson ether synthesis.

Answer :

Williamson ether synthesis is a reaction forming ether from a primary alkyl halide via S _N 2 reaction.

1649966930561

Question 11.18(iv) Explain the following with an example.(iv) Unsymmetrical ether.

Answer :

If the alkyl or aryl groups attached to the oxygen atom are different, then it is mixed or unsymmetrical ether.

Eg: $C_2H_5-O-CH_3\ and\ C_2H_5-O-C_6H_5$

Question 11.19 . Write the mechanism of acid dehydration of ethanol to yield ethene.

Answer :

Alcohols undergo dehydration (removal of a molecule of water) to form alkenes on treating with a protic acid. Ethanol undergoes dehydration by heating it with concentrated sulphuric acid at 443 K.

1649966962919

Question 11.20(i) How are the following conversions carried out?
(i) Propene $\rightarrow$ Propan-2-ol.

Answer :

Acid catalysed hydration of propene produces propan-2-ol.

1649966998750

Question 11.20(ii) How are the following conversions carried out?
(ii) Benzyl chloride $\rightarrow$ Benzyl alcohol.

Answer :

Benzyl chloride treated with NaOH followed by acidification produces benzyl alcohol.

12th_chemistry_11_1_8_1466307644_14

Question 11.20(iii) How are the following conversions carried out?
(iii) Ethyl magnesium chloride $\rightarrow$ Propan-1-ol.

Answer :

Ethyl magnesium chloride treated with formaldehyde followed by hydrolysis produces propan-1-ol.

1649967048713

Question 11.20(iv) How are the following conversions carried out?
(iv) Methyl magnesium bromide $\rightarrow$ 2-Methylpropan-2-ol.

Answer :

Methyl magnesium bromide treated with propane, gives 2-methylpropane-2-ol on hydrolysis.

1649967086833

Question 11.21(i) Name the reagents used in the following reactions:
(i) Oxidation of a primary alcohol to carboxylic acid.

Answer :

Acidic/neutral/alkaline potassium permanganate $(KMnO_4)$ or acidified $K_2Cr_2O_7$

Question 11.21(ii) Name the reagents used in the following reactions:
(ii) Oxidation of a primary alcohol to aldehyde.

Answer :

The reagent used for oxidation of primary alcohol to aldehyde is Pyridinium chlorochromate (PCC) .

Question 11.21(iii) Name the reagents used in the following reactions:
(iii) Bromination of phenol to 2,4,6-tribromophenol.

Answer :

Reagents used in the bromination of phenol to 2,4,6-tribromophenol is Bromine water

Question 11.21(iv) Name the reagents used in the following reactions:

(iv) Benzyl alcohol to benzoic acid.

Answer :

Reagent used in the benzyl alcohol to benzoic acid isAcidified $KMnO_4$ (potassium permanganate)

Question 11.21(v) Name the reagents used in the following reactions:
(v) Dehydration of propan-2-ol to propene.

Answer :

Reagents used in the dehydration of propan-2-ol to propene is Concentrated Phosphoric acid.

Question 11.21(vi) Name the reagents used in the following reactions:
(vi) Butan-2-one to butan-2-ol.

Answer :

Reagent used in the butan-2-one to butan-2-ol is $LiAlH_4\ or\ NaBH_4$

Question 11.22 Give reason for the higher boiling point of ethanol in comparison to methoxymethane.

Answer :

Ethanol undergoes intermolecular hydrogen bonding due to the presence of -OH group. Therefore, extra energy is required to break those hydrogen bonds. Whereas methoxymethane does not make H-bonds and hence ethanol has a higher boiling point than methoxymethane.

Question 11.23(i) Give IUPAC names of the following ethers:

1649967122741

Answer :

IUPAC names of the given ether is 1-Ethoxy-2-methylpropane

Question 11.23(ii) Give IUPAC names of the following ethers:

1649967185868

Answer :

IUPAC names of the given ether is 2-Chloro-1-methoxyethane

Question 11.23(iii) Give IUPAC names of the following ethers:

1649967223743

Answer :

IUPAC names of the given ether is 4-Nitroanisole

Question 11.23(iv) Give IUPAC names of the following ethers:

1649967263588

Answer :

IUPAC names of the given ether is 1-Methoxypropane

Question 11.23(v) Give IUPAC names of the following ethers:

1649967298676

Answer :

IUPAC names of the given ether is 4-Ethoxy-1, 1-dimethylcyclohexane

Question 11.23(vi) Give IUPAC names of the following ethers:

1649967335363

Answer :

IUPAC names of the given ether is Ethoxybenzene

Question 11.24(i) Write the names of reagents and equations for the preparation of the following ethers by Williamson’s synthesis:
(i) 1-Propoxypropane

Answer :

Names of reagents and equations for the preparation of the 1-Propoxypropane ether by Williamson’s synthesis:-

1649967375627

Question 11.24(ii) Write the names of reagents and equations for the preparation of the following ethers by Williamson’s synthesis:
(ii) Ethoxybenzene

Answer :

Names of reagents and equations for the preparation of the Ethoxybenzene ether by Williamson’s synthesis:-

1649967410030 with NaBr as side product.

Question 11.24(iii) Write the names of reagents and equations for the preparation of the following ethers by Williamson’s synthesis:
(iii) 2-Methoxy-2-methylpropane

Answer :

Names of reagents and equations for the preparation of the2-Methoxy-2-methylpropane ether by Williamson’s synthesis:-

1649967458991

Question 11.24(iv) Write the names of reagents and equations for the preparation of the following ethers by Williamson’s synthesis: (iv) 1-Methoxyethane

Answer :

Names of reagents and equations for the preparation of the1-Methoxyethane ether by Williamson’s synthesis:-

1649967498923

Question 11.25 Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.

Answer :

Williamson synthesis involves $S_N2$ attack by alkoxide ion on a primary alkyl halide. But if secondary or tertiary alkyl halides are taken then alkenes would be produced because elimination would take place. This is because alkoxides are nucleophiles as well as strong bases.

12th_chemistry_11_1_8_1466308233_67

Question 11.26 How is 1-propoxypropane synthesised from propan-1-ol? Write mechanism of this reaction.

Answer :

Propan-1-ol on dehydration using protic acids such as sulphuric acid gives 1-propoxypropane.

Mechanism of this reaction:

Formation of protonated alcohol.

1649967562663

Formation of carbocation: It is the slowest step and hence, the rate determining step of the reaction.

1649967580906

Formation of ethene by the elimination of a proton.

1649967599892

Question 11.27 Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.

Answer :

The formation of ethers by dehydration of a primary alcohol is an S _N 2 reaction. In case of secondary or tertiary alcohols, the alkyl group is hindered and hence elimination dominates substitution. Therefore alkenes are formed in place of ethers.

Question 11.28(i) Write the equation of the reaction of hydrogen iodide with:
(i) 1-propoxypropane

Answer :

1-propoxypropane reacts with HI to give propan-1-ol and 1-iodopropane as the products.

1649967642248

Question 11.28(ii) Write the equation of the reaction of hydrogen iodide with: (ii) methoxybenzene

Answer :

Methoxybenzene reacts with HI to give phenol and iodomethane.

1649967678156

Question 11.28(iii) Write the equation of the reaction of hydrogen iodide with: (iii) benzyl ethyl ether.

Answer :

Benzyl ethyl ether reacts with HI to give benzyl iodide and ethanol.

1649967720536

Question 11.29(i) Explain the fact that in aryl alkyl ethers (i) the alkoxy group activates the benzene ring towards electrophilic substitution

Answer :

Due to the +R effect of the alkoxy group, it increases the electron density of the benzene ring pushing electrons into the ring making the benzene ring activated towards electrophilic substitution reactions.

Question 11.29(ii) Explain the fact that in aryl alkyl ethers (ii) it directs the incoming substituents to ortho and para positions in benzene ring.

Answer :

1649967762793

The above resonating structures shows that the electron density increases more at the ortho and para positions as compared to the meta positions. Hence, the alkoxy group directs the incoming substituents to ortho and para positions in the benzene ring.

Question 11.30. Write the mechanism of the reaction of HI with methoxymethane.

Answer :

Following is the mechanism:

1. Protonation of methoxymethane

1649967808094

2. Nucleophilic attack of $I^-$

1649967828420

3. If HI is in excess, then methanol formed in step 2 reacts with another HI molecule and gets converted to methyl iodide at a high temperature.

1649967848758

Question 11.31(i) Write equations of the following reactions:
(i) Friedel-Crafts reaction – alkylation of anisole.

Answer :

Fridel Craft reaction(Alkylation):

1649967890235

Question 11.31(ii) Write equations of the following reactions: (ii) Nitration of anisole.

Answer :

Nitration of anisole:

1649967923121

Question 11.31(iii) Write equations of the following reactions: (iii) Bromination of anisole in ethanoic acid medium.

Answer :

Bromination of anisole in ethanoic acid medium:

1649967952984

Question 11.31(iv) Write equations of the following reactions: (iv) Friedel-Craft’s acetylation of anisole.

Answer :

Friedel-Craft’s acetylation of anisole:

1649967984977

Question 11.32 Show how would you synthesise the following alcohols from appropriate alkenes?

1594976641206 1594976638647

Answer :

(i) 1649968028846

(ii) 1649968047019

(iii) 1649968066505

(iv) 1649968087729

Question 11.33 When 3-methylbutan-2-ol is treated with HBr, the following reaction takes
place:

1594976469500 1594976466780
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.

Answer :

Mechanism for the reaction 3-methylbutan-2-ol is treated with HBr

1649968132938

Chemistry Chapter 11 NCERT Solutions Insights

Alcohols Phenols and Ethers Class 12 NCERT solutions has answers to a total of 12 topic wise questions and 33 questions in the exercise. In the CBSE boards exam, the weightage of this chapter is 4 marks hence it is recommended to solve all the exercises of the book to get good marks. You will find all the NCERT solutions for Class 12 Chemistry chapter 11 Alcohols, Phenols and Ethers here free of cost.

Also Read| NCERT Exemplar Solutions for Alcohols Phenols and Ethers

By referring to the NCERT solutions for class 12, students can understand all the important concepts and practice questions well enough before their examination. Alcohols are the basic compound for the formation of detergents, phenols are the basic compound for the formation of antiseptics and ethers is the basic compound for the formation of fragrances.

Check Here For An Easy Way To Master The Periodic Table 7 min read Mar 05, 2022 Read More Resources KVPY SA Test Series

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Topics and Sub-topics of NCERT Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers-

11.1 Classification

11.2 Nomenclature

11.3 Structures of Functional Groups

11.4 Alcohols and Phenols

11.5 Some Commercially Important Alcohols

11.6 Ethers

NCERT Solutions Class 12 Chemistry Chapter Wise

Chapter 1	The Solid State
Chapter 2	Solutions
Chapter 3	Electrochemistry
Chapter 4	Chemical Kinetics
Chapter 5	Surface chemistry
Chapter 6	General Principles and Processes of isolation of elements
Chapter 7	The P-block elements
Chapter 8	The d and f block elements
Chapter 9	Coordination compounds
Chapter 10	Haloalkanes and Haloarenes
Chapter 11	Alcohols, Phenols and Ethers
Chapter 12	Aldehydes, Ketones and Carboxylic Acids
Chapter 13	Amines
Chapter 14	Biomolecules
Chapter 15	Polymers
Chapter 16	Chemistry in Everyday life

NCERT Solutions for Class 12 Subject wise

NCERT Solutions for class 12 biology
NCERT solutions for class 12 maths
NCERT solutions for class 12 chemistry
NCERT Solutions for class 12 physics

Benefits of NCERT Solutions for class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers

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It will be easy to revise because the detailed solutions will help you to remember the concepts and fetch you good marks.
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