/ Preparation Chemistry Ncert Solutions Class 12th
Alcohols and phenols are created by replacing a hydrogen atom in an aliphatic, hydrocarbon and aromatic with an -OH group. These compounds have industry-wide applications and are also used in day-to-day life. The daily use of these compounds containing -OH groups includes the cotton used for fabrics, the sugar we eat, and the paper we use for writing. Class 12 Chemistry Alcohol Phenol and Ether is an important chapter for Class 12 Science students preparing for the CBSE Board exam and JEE Mains.
After studying the Alcohol Phenol and Ether NCERT Solutions, the students will be able to name phenols, alcohols, and ethers according to IUPAC nomenclature, discuss reactions involved in the preparation of phenols, alcohols, and ethers, and correlate physical properties of these compounds with their structures. Students must master the fundamentals of the Alcohol Phenol Ether Class 12 Chemistry.
Get access to the comprehensive NCERT Solutions of Maths, Physics, Chemistry of Class 11 and Class 12. Students will also get the key topics and PDFs of each chapter.
- NCERT Chemistry Class 12 Chapter 7 Alcohol, Phenol and Ethers: Key Topics and Important Reactions
- Download NCERT Class 12 Chemistry Solutions – Alcohol, Phenol and Ether PDF
- Alcohol, Phenol and Ethers Solutions
NCERT Chemistry Class 12 Chapter 7 Alcohol, Phenol and Ethers: Key Topics and Important Reactions
During the preparation of Alcohol Phenol Ether, the students should focus on the topics like properties, preparation, and reactions of the alcohols, phenols and ethers. They should also read about the identification and distinguishing tests included in this chapter. Here are the topics covered in this chapter:
| Exercise | Topics Covered |
|---|---|
| 7.1 | Classification |
| 7.2 | Nomenclature |
| 7.3 | Structures of Functional Groups |
| 7.4 | Alcohols and Phenols |
| 7.5 | Some Commercially Important Alcohols |
| 7.6 | Ethers |
Alcohol Phenol and Ether Weightage in NEET, JEE Mains
| Exam | Weightage |
|---|---|
| NEET | 4% |
| JEE Main | 4-5% |
Important Topics covered in Class 12 Chemistry Chapter 7: Alcohols, Phenols, and Ethers
- Nomenclature and Structure of Alcohols, Phenols, and Ethers
- Preparation of Alcohols
- Physical Properties of Alcohols
- Chemical Reactions of Alcohols
- Uses of Alcohols
- Preparation of Phenols
- Physical Properties of Phenols
- Chemical Reactions of Phenols
- Uses of Phenols
- Preparation of Ethers
- Physical Properties of Ethers
- Chemical Reactions of Ethers
- Uses of Ethers
Important Reactions of NCERT Class 12 Chemistry Alcohols, Phenols, and Ethers1. Preparation of Alcohols
From Alkenes (Hydration Reaction)
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Acid-catalyzed hydration: CH₂=CH₂ + H₂O → CH₃CH₂OH
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Hydroboration-Oxidation: CH₂=CH₂ + BH₃ → CH₃CH₂BH₂ → CH₃CH₂OH
From Carbonyl Compounds
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Reduction of Aldehydes & Ketones:
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R-CHO + H₂ → R-CH₂OH
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R-CO-R' + H₂ → R-CHOH-R'
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Grignard Reaction:
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R-MgX + HCHO → R-CH₂OH
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From Carboxylic Acids & Esters
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Reduction of Carboxylic Acids:
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RCOOH + LiAlH₄ → RCH₂OH
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Reduction of Esters:
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RCOOR' + LiAlH₄ → RCH₂OH + R'OH
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2. Chemical Reactions of Alcohols
Oxidation Reactions
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Primary Alcohol → Aldehyde → Carboxylic Acid:
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R-CH₂OH + [O] → R-CHO + [O] → RCOOH
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Secondary Alcohol → Ketone:
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R-CHOH-R' + [O] → R-CO-R'
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Tertiary Alcohols do not undergo oxidation easily.
Dehydration (Elimination Reaction)
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CH₃CH₂OH → CH₂=CH₂ + H₂O (conc. H₂SO₄, 443K)
Reaction with HX (Haloalkane Formation)
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R-OH + HX → R-X + H₂O
Lucas Test (To distinguish primary, secondary, and tertiary alcohols)
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ROH + HCl → RCl (ZnCl₂ as catalyst)
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Tertiary alcohols react immediately (Cloudy solution)
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Secondary alcohols react slowly
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Primary alcohols do not react at room temperature
3. Preparation of Phenols
From Chlorobenzene (Dow’s Process)
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C₆H₅Cl + NaOH → C₆H₅ONa + H₂O
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C₆H₅ONa + HCl → C₆H₅OH
From Benzene Sulphonic Acid
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C₆H₆SO₃H + NaOH → C₆H₅ONa + Na₂SO₃
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C₆H₅ONa + HCl → C₆H₅OH
From Diazonium Salts
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C₆H₅N₂⁺Cl⁻ + H₂O → C₆H₅OH + N₂ + HCl
4. Chemical Reactions of Phenols
Acidic Nature of Phenol
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C₆H₅OH + NaOH → C₆H₅ONa + H₂O
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C₆H₅OH + Na → C₆H₅ONa + H₂
Electrophilic Substitution Reactions
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Nitration:
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C₆H₅OH + HNO₃ → o-Nitrophenol + p-Nitrophenol
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Halogenation:
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C₆H₅OH + Br₂ → 2,4,6-Tribromophenol (White ppt.)
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Friedel-Crafts Alkylation:
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C₆H₅OH + CH₃Cl → p-Cresol
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Reimer-Tiemann Reaction (Formylation of Phenol)
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C₆H₅OH + CHCl₃ + NaOH → o-Hydroxybenzaldehyde
Kolbe’s Reaction (Carboxylation of Phenol)
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C₆H₅ONa + CO₂ → Salicylic Acid
Oxidation of Phenols
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Phenol + Oxidizing agent → Quinone
5. Preparation of Ethers
Williamson’s Synthesis
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R-O⁻Na⁺ + R'-X → R-O-R' + NaX
From Alcohols (Dehydration Method)
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2R-OH → R-O-R + H₂O (Conc. H₂SO₄, 413K)
6. Chemical Reactions of Ethers
Cleavage of Ethers by HI
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R-O-R' + HI → R-I + R'-OH
Electrophilic Substitution in Aromatic Ethers
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Nitration:
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C₆H₅OCH₃ + HNO₃ → o-Nitroanisole + p-Nitroanisole
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Halogenation:
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C₆H₅OCH₃ + Br₂ → 2,4-Dibromoanisole
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Download NCERT Class 12 Chemistry Solutions – Alcohol, Phenol and Ether PDF
Students are advised to download the Alcohol Phenol and Ether NCERT PDF from the link given here. The PDF is created by the subject matter experts at Shiksha. It provides accurate and reliable study material for CBSE Board exam, NEET, and JEE Mains preparation.
Class 12 Chemistry Chapter 7 Alcohol, Phenol and Ether NCERT solutions: Download Free PDF
For the chapter-wise key topics, PDFs, and weightage information of Class 12 Chemistry, check Class 12 Chemistry NCERT Solutions.
Alcohol, Phenol and Ethers Solutions
| Q 11.1 Classify the following as primary, secondary and tertiary alcohols: |
Ans
It is primary alcohol because carbon which carries the –OH group is only attached to one alkyl group.
It is primary alcohol because carbon which carries the –OH group is only attached to one alkene group. It is primary alcohol because the carbon which carries the –OH group is only attached to one propyl group. It is secondary alcohol because the carbon which carries the –OH group is joined directly to methyl and benzene. It is secondary alcohol because the carbon which carries the –OH group is joined directly to two different alkyl groups. |
| Q 11.2 Identify allylic alcohols in the above examples. |
| Ans Allylic alcohol is an organic compound which has the structural formula CH2 = CHCH2OH. In other words, in these alcohols, the the-OH group is attached to sp2 hybridized carbon next to the carbon-carbon double bond, that is to an allylic carbon. Therefore, in the above examples, the following are the allylic alcohols. (ii) H2C = CH – CH2OH and |
| Q 11.3 Name the following compounds according to IUPAC system. |
| Ans (i) 3-chloroethyl-2-isopropylpentan-1-ol (ii) 2,5-Dimethylhexane-1,3-diol (iv) 3-Bromocyclohexanol (v) Hex-1-en-3-ol (vi) 2-Bromo-3-methylbut-2-en-1-ol |
| Q 11.4 Show how are the following alcohols prepared by the reaction of a suitable Grignard reagent on methanal? |
| Ans In the Grignard reagent reaction, the first step of the reaction is the nucleophilic addition of Grignard reagent to the carbonyl group to form an adduct, Hydrolysis of adduct results in the formation of alcohol. Here, is the general reaction with Grignard reagent below:- From here, it is clear that HCHO gives CH2OH groups, so R of Grignard reagent is the remaining part of given alcohols. Thus, select the suitable Grignard reagent by substituting the value of R. Now we can see the reaction given below:- Methanal reacts with iso-propyl magnesium bromide, in presence of dry ether gives an additional compound. And this additional compound on reaction with H2O /H+ gives iso-butyl alcohol (i.e., 2-methylpropane-1-ol) as one of the final product. Methanal reacts with cyclohexyl magnesium bromide, in presence of dry ether, which gives an intermediate product. This intermediate product when reacts with given reagent, as shown above, gives cyclohexyl methanol as a product. |
Commonly asked questions
11.30 Explain the following with an example.
(i) Kolbe’s reaction.
(ii) Reimer-Tiemann reaction.
(iii) Williamson ether synthesis.
(iv) Unsymmetrical ether.
11.33 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.
11.8 Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.
11.15
(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.
11.17 Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
11.32
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.
11.40 Write the equation of the reaction of hydrogen iodide with: (i) 1-propoxypropane (ii) Methoxybenzene and (iii) Benzyl ethyl ether.
11.55 (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.
11.4 Show how are the following alcohols prepared by the reaction of a suitable Grignard reagent on methanal?
11.27 Explain why is ortho nitrophenol more acidic than ortho methoxyphenol ?
11.28 Explain how does the –OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?
11.29 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.
11.3 Name the following compounds according to IUPAC system.
11.1 Classify the following as primary, secondary and tertiary alcohols:
11.2 Identify allylic alcohols in the above examples.
11.5 Write structures of the products of the following reactions:
11.6 Give structures of the products you would expect when each of the following Methylbutan alcohol reacts with (a) HCl –ZnCl2 (b) HBr and (c) SOCl2
11.9 Write the equations involved in the following reactions: (i) Reimer - Tiemann reaction (ii) Kolbe’s reaction
11.10 Write the reactions of Williamson synthesis of 2-ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.
11.11 Which of the following is an appropriate set of reactants for the preparation of 1- methoxy-4-nitrobenzene and why?
11.12 Predict the products of the following reactions:
11.13 Write IUPAC names of the following compounds:
11.14bWrite 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
11.16 Explain why propanol has higher boiling point than that of the hydrocarbon, butane?
11.18 What is meant by hydroboration-oxidation reaction? Illustrate it with an example.
11.19 Give the structures and IUPAC names of monohydric phenols of molecular formula, C7H8O.
11.20 While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason
11.21 Give the equations of reactions for the preparation of phenol from cumene.
11.22 Write chemical reaction for the preparation of phenol from chlorobenzene.
11.23 Write the mechanism of hydration of ethene to yield ethanol
11.24 You are given benzene, conc. H2SO4 and NaOH. Write the equations for the preparation of phenol using these reagents.
11.25
Show how will you synthesise:
(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?
11.26 Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.
11.31 Write the mechanism of acid dehydration of ethanol to yield ethene.
11.34 Give reason for the higher boiling point of ethanol in comparison to methoxymethane.
11.35 Give IUPAC names of the following ethers:
11.36 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
11.37 Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.
11.38 How is 1-propoxypropane synthesised from propan-1-ol? Write mechanism of this reaction.
11.39 Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason
11.41
Explain the fact that in aryl alkyl ethers
(i) The alkoxy group activates the benzene ring towards electrophilic substitution
(ii) It directs the incoming substituents to ortho and para positions in benzene ring.
11.42 Write the mechanism of the reaction of HI with methoxymethane.
11.43
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.
11.45 When 3-methylbutan-2-ol is treated with HBr, the following reaction takes place: 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.
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.
11.46 Write structures of the products of the following reactions:
11.47 Give structures of the products you would expect when each of the following Methylbutan alcohol reacts with (a) HCl –ZnCl2 (b) HBr and (c) SOCl2.
11.49 Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.
11.50 Write the equations involved in the following reactions: (i) Reimer - Tiemann reaction (ii) Kolbe’s reaction
11.51 Write the reactions of Williamson synthesis of 2-ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.
11.52 Which of the following is an appropriate set of reactants for the preparation of 1- methoxy-4-nitrobenzene and why?
11.53 Predict the products of the following reactions:
11.54 Write IUPAC names of the following compounds:
11.54 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.
11.56 Explain why propanol has higher boiling point than that of the hydrocarbon, butane?
11.57 Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
11.58 What is meant by hydroboration-oxidation reaction? Illustrate it with an example.
11.60 Give the structures and IUPAC names of monohydric phenols of molecular formula, C7H8O.
11.61 While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason
11.62 Give the equations of reactions for the preparation of phenol from cumene.
11.63 Write chemical reaction for the preparation of phenol from chlorobenzene.
11.64 Write the mechanism of hydration of ethene to yield ethanol
11.65 You are given benzene, conc. H2SO4 and NaOH. Write the equations for the preparation of phenol using these reagents.
11.66 Show how will you synthesise: (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?
11.67 Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.
11.68 Explain why is ortho nitrophenol more acidic than ortho methoxyphenol ?
11.69 Explain how does the –OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?
11.70 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.
11.71 Explain the following with an example. (i) Kolbe’s reaction. (ii) Reimer-Tiemann reaction. (iii) Williamson ether synthesis. (iv) Unsymmetrical ether.
11.72 Write the mechanism of acid dehydration of ethanol to yield ethene.
11.73 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.
11.74 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.
11.75 Give reason for the higher boiling point of ethanol in comparison to methoxymethane.
11.76 Give IUPAC names of the following ethers:
11.77 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
11.78 Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.
11.79 How is 1-propoxypropane synthesised from propan-1-ol? Write mechanism of this reaction.
11.80 Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.
11.81 Write the equation of the reaction of hydrogen iodide with: (i) 1-propoxypropane (ii) Methoxybenzene and (iii) Benzyl ethyl ether.
11.82 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.
11.83 Write the mechanism of the reaction of HI with methoxymethane.
11.84 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.
11.85 Show how would you synthesise the following alcohols from appropriate alkenes?
11.86 When 3-methylbutan-2-ol is treated with HBr, the following reaction takes place: 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.
11.7 Predict the major product of acid catalysed dehydration of (i) 1-methylcyclohexanol and (ii) Butan-1-ol
Chemistry Ncert Solutions Class 12th Exam
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