Alcohols, Phenols and Ethers

Alcohols, Phenols and Ethers

Book Solutions

1



Answer

(i) 2, 2, 4-Trimethylpentan-3-ol

(ii) 5-Ethylheptane-2, 4-diol

(iii) Butane-2, 3-diol

(iv) Propane-1, 2, 3-triol

(v) 2-Methylphenol

(vi) 4-Methylphenol

(vii) 2, 5-Dimethylphenol

(viii) 2, 6-Dimethylphenol

(ix) 1-Methoxy-2-methylpropane

(x) Ethoxybenzene

(xi) 1-Phenoxyheptane

(xii) 2-Ethoxybutane

Exercise

2

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) 3-Chloromethylpentan-1-ol.

Answer



Exercise

3

Name the following compounds according to IUPAC system.

Answer

Eight isomers are possible. These are:



Exercise

4

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

Answer

Exercise

5

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

Answer

Exercise

6

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

Answer

Exercise

7

Give the structures and IUPAC names of monohydric phenols of molecular formula, C7H8O.

Answer

Exercise

8

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

Answer

Exercise

9

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

Answer

Exercise

10

Write chemical reaction for the preparation of phenol from chlorobenzene.

Answer

Exercise

11

Write the mechanism of hydration of ethene to yield ethanol.


Answer

Exercise

12

You are given benzene, conc. H2SO4 and NaOH. Write the equations for the preparation of phenol using these reagents.

Answer

Exercise

13

Show how will you synthesize:

(i) 1-phenylethanol from a suitable alkene.

(ii) cyclohexylmethanol using an alkyl halide by an SN2 reaction.

(iii) pentan-1-ol using a suitable alkyl halide?

Answer

Exercise

14

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

Answer



Exercise

15

Explain why is ortho nitrophenol more acidic than ortho methoxyphenol?


Answer

Exercise

16

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

Answer

Exercise

17

Give equations of the following reactions:

(i) Oxidation of propan-1-ol with alkaline KMnO4 solution.

(ii) Bromine in CS2 with phenol.

(iii) Dilute HNO3 with phenol.

(iv) Treating phenol with chloroform in presence of aqueous NaOH.

Answer

Exercise

18

Explain the following with an example.

(i) Kolbe’s reaction.

(ii) Reimer-Tiemann reaction.

(iii) Williamson ether synthesis.

(iv) Unsymmetrical ether.

Answer



Exercise

19

Write the mechanism of acid-catalysed dehydration of ethanol to yield ethene.


Answer

Exercise

20

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.

Answer


Exercise

21

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.

Answer

(i) Acidified potassium permanganate

(ii) Pyridinium chlorochromate (PCC)

(iii) Bromine water

(iv) Acidified potassium permanganate

(v) 85% phosphoric acid

(vi) NaBH4 or LiAlH4

Exercise

22

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

Answer

Exercise

23

Give IUPAC names of the following ethers:

Answer

(i) 1-Ethoxy-2-methylpropane

(ii) 2-Chloro-1-methoxyethane

(iii) 4-Nitroanisole

(iv) 1-Methoxypropane

(v) 4-Ethoxy-1, 1-dimethylcyclohexane

(vi) Ethoxybenzene

Exercise

24

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

Answer

Exercise

25

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

Answer

Williamson’s synthesis is a versatile method for the synthesis of both symmetrical and unsymmetrical ethers. However, for the synthesis of unsymmetrical ethers, a proper choice of reactants is necessary. Since Williamson’s synthesis occurs by SN2 mechanism and primary alkyl halides are most reactive in SN2 reaction, therefore, best yields of unsymmetrical ethers are obtained when the alkyl halides are primary and the alkoxide may be primary, secondary or tertiary. For example, tert-butyl ethyl ether is prepared by treating ethyl bromide with sodium tert-butoxide.

Exercise

26

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

Answer

Exercise

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 alcohol is a bimolecular reaction (SN2) involving the attack of an alcohol molecule on a protonated alcohol molecule. In the method, the alkyl group should be unhindered. In case of secondary or tertiary alcohols, the alkyl group is hindered. As a result, elimination dominates substitution. Hence, in place of ethers, alkenes are formed.
Exercise

28

Write the equation of the reaction of hydrogen iodide with:

(i) 1-propoxypropane

(ii) Methoxybenzene and

(iii) Benzyl ethyl ether

Answer

Exercise

29

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.


Answer

Exercise

30

Write the mechanism of the reaction of HI with methoxy methane.

Answer

Exercise

31

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.

Answer


Exercise

32

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

Answer



Exercise

33

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

Answer

Exercise