NCERT Solutions for class 12th Chemistry Chapter 11 Alchohols, Phenols and Ethers

NCERT INTEXT QUESTIONS

Question 1. Classify the following as primary, secondary and tertiary alcohols.

Question 2. Identify allylic alcohols in the above examples.

Question 3. Name the following compounds according to IUPAC system.

Question 4. Show how are the following alcohols prepared by the reaction of a suitable Grignard reagent on methanal?

Question 5. Write structures of the products of the following reactions:

Question 6. Give structures of the products you would expect when each of the following alcohol reacts with (a) HCI-ZnCl₂ (b) HBr and (c) SOCl₂.
(i) Butan-1-ol
(ii) 2-Methylbutan-2-ol

Question 7. Predict the major product of acid-catalysed dehydration of

Question 8. Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.

Question 9. Write the equations involved in the following reactions:
(i) Reimer – Tiemann reaction
(ii) Kolbe’s reaction

Question 10. Write the reactions of Williamson’s synthesis of 2-ethoxy-3-methylpentane starting from ethanol and 2,3-dimethylpentan-1-ol.

Question 11. Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why?

Question 12. Predict the products of the following reactions:

Exercise

Question 1. Write IUPAC names of the following compounds:

Question 2. Write structures of the compounds whose IUPAC names are as follows:

Question 3. (i) Draw the structures of all isomeric alcohols of molecular formula C₅H₁₂O and give their IUPAC names.
(ii) Classify the isomers of alcohols in question 11.3 (i) as primary, secondary and tertiary alcohols.

Question 4. Explain why propanol has higher boiling point than that of the hydrocarbon, butane?

Question 5. Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.

Question 6. What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

Question 7. Give the structures and IUPAC names of monohydric phenols of molecular formula, C₇H₈O.

Question 8. While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.

Question 9. Give the equations of reactions for the preparation of phenol from cumene.

Question 10. Write chemical reaction for the preparation of phenol from chlorobenzene.

Question 11. Write the mechanism of hydration of ethene to yield ethanol.

Question 12. You are given benzene, cone. H₂SO₄and NaOH. Write the equations for the preparation of phenol using these reagents.

Question 13. Show how will you synthesise?
(i) 1-Phenylethanol from a suitable alkene.
(ii) Cyclohexylmethanol using an alkyl halide by an S_N2 reaction.
(iii) Pentan-1-ol using a suitable alkyl halide?

Question 14. Give two reactions that show the acidic nature of phenol. Compare its acidity with that of ethanol.

Question 15. Explain why is ortho-nitrophenol more acidic than ortho-methoxyphenol?

Question 16. Explain how does the-OH group attached to a carbon of benzene ring activates it towards electrophilic substitution?

Question 17. Give equations of the following reactions

Question 18. Explain the following with an example
(i) Kolbe’s reaction (ii) Reimer – Tiemann reaction
(iii) Williamson ether synthesis (iv) Unsymmetrical ether

Question 19. Write the mechanism of acid dehydration of ethanol to yield ethene.

Question 20. How are the following conversions carried out?

Question 21. Name the reagents used in the following reactions:

Sol. (i) Acidified potassium dichromate or neutral/acidic/alkaline potassium permanganate.

Question 22. Give reason for the higher boiling point of ethanol in comparison to methoxymethane.

Question 23. Give IUPAC names of the following ethers.

Question 24. Write the names of reagents and equations for the preparation of the following ethers by Williamson’s synthesis

Question 25. Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.

Sol. 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 S_N2 mechanism and primary alkyl halides are most reactive in S_N2 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-butylethyl ether is prepared by treating ethyl bromide with sodium tert-butoxide.

Question 26. How is 1-propoxypropane synthesised from propan-1-ol? Write the mechanism of this reaction.

Question 27. Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.

Question 28. Write the equation of the reaction of hydrogen iodide with

Question 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.

Question 30. Write the mechanism of the reaction of HI with methoxymethane.

Question 31. Write equations of the following reactions:
(i) Friedel-Craft’s reaction -alkylation of anisole
(ii) Nitration of anisole.
(iii) Brornination of anisole in ethanoic acid medium
(iv) Friedel-Craft’s acetylation of anisole.

Question 32. Show how would you synthesise the following alcohols from appropriate alkenes?

Question 33. When 3-methylbutan 2-ol is treated with HBr, the following reaction takes place:

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