Chemistry

Alcohols, Phenols and Ethers

Question:

Assertion (A): IUPAC name of the compound
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-57
Reason (R): In IUPAC nomenclature, ether is regarded as hydrocarbon derivative in which a hydrogen atom is replaced by -OR or -OAr group [where R = alkyl group and Ar = aryl group]

Answer:

(d) IUPAC name of the compound is 2-propoxypropane.

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Alcohols, Phenols and Ethers

Q 1.

Classify the following as primary, secondary and tertiary alcohols.
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-1
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-2
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-3

Q 2.

Assertion (A): Phenols give o-nitrophenol and p-nitrophenol on nitration with cone. HNO3 and H2SO4 mixture.
Reason (R): -OH group in phenol is o-,p-directing.

Q 3.

Give equations of the following reactions:
(i)Oxidation of propan-l-ol with alkaline KMnO4 solution.
(ii)Bromine in CS2 with phenol.
(iii)Dilute HNO3 acid with phehoL
(iv)Treating phenol with chloroform in presence of aqueous NaOH.

Q 4.

Explain why alcohols and ethers of comparable molecular mass have different boiling points.

Q 5.

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

Q 6.

Suggest a reagent for conversion of ethanol to ethanal.

Q 7.

How can propan-2-one be converted into tert-butyl alcohol?

Q 8.

Which of the following species can act as the strongest base?
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-12

Q 9.

Out of o-nitrophenol and p-nitrophenol, which is more volatile? Explain.

Q 10.

Assertion (A): Boiling points of alcohols and ethers are high.
Reason (R): They can form intermolecular hydrogen bonding.

Q 11.

Arrange the following compounds in increasing order of acidity and give a suitable explanation:
Phenol, o-Nitrophenol, o-Cresol

Q 12.

Which of the following compounds are/is aromatic alcohol?  
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-6

Q 13.

What is denatured alcohol?

Q 14.

Assertion (A): o-Nitrophenol is less soluble in water than the m- and p-isomers.
Reason (R): m-Nitrophenol and p-Nitrophenol exists as associated molecules.

Q 15.

Write the equations involved in the following reactions:
(i) Reimer-Tiemann reaction
(ii) Kolbe's reaction

Q 16.

Write structures of the compounds whose IUPAC names are as follows:
(i)2-Methylbutan-2-ol
(ii)l-Phcnylpropan-2-ol
(iii)3,5-DimethyIhexane-l,3,5-triol
(iv)2,3-Dicthylphenol
(v)1-Ethoxypropane
(vi)2-Ethoxy-3-methylpentane
(vii) Cyclohexylmethanol
(viii) 3-Cyclohexylpcntan-3-ol
(ix)Cyclopcnt-3-en-l-ol
(x)4-ChIoro-3-ethylbutan-l-ol

Q 17.

Write the mechanism of hydration of ethene to yield ethanol.

Q 18.

Give IUPAC names of the following ethers.
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-29

Q 19.

Mark the correct increasing order of reactivity of the following compounds with HBr/HCl.
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-15

Q 20.

Name the factors responsible for the solubility of alcohols in water.

Q 21.

Name the enzymes and write the reactions involved in the preparation of ethanol from sucrose by fermentation.

Q 22.

Assertion (A): p-Nitrophcnol is more acidic than phenol.
Reason (R): Nitro group helps in the stabilization of the phenoxide ion by dispersal of negative charge due to resonance.

Q 23.

Assertion (A): IUPAC name of the compound
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-57
Reason (R): In IUPAC nomenclature, ether is regarded as hydrocarbon derivative in which a hydrogen atom is replaced by -OR or -OAr group [where R = alkyl group and Ar = aryl group]

Q 24.

Assertion (A): Bond angle in ethers is slightly less than the tetrahedral angle. Reason (R): There is a repulsion between the two bulky (-R) groups.

Q 25.

Identify aliylic alcohols in the above examples.

Q 26.

Which of the following is an appropriate set of reactants for the preparation of l-methoxy-4- nitrobenzene and why?
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-20

Q 27.

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

Q 28.

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

Q 29.

Write the mechanism of the reaction of HI with methoxymethane.

Q 30.

Which of the following are benzylic alcohols?
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-21

Q 31.

Why is the reactivity of all three classes of alcohols with cone. HCl and ZnCl2 (Lucas reagent) different?

Q 32.

Assertion (A): Like bromination of benzene, bromination of phenol is also carried out in the presence of Lewis acid.
Reason (R): Lewis acid polarizes the bromine molecule.

Q 33.

Explain a process in which a biocatalyst is used in industrial preparation of a compound known to you.

Q 34.

Predict the major product of acid catalysed dehydration of
(i) 1-nicthylcyclohcxanoland
(ii) butan-1-ol

Q 35.

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

Q 36.

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

Q 37.

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

Q 38.

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)Brominationofphenolto2,4,6-tribromophenol
(iv)Benzyl alcohol to benzoic acid.
(v)Dehydration of propan-2-oI to propene.
(vi)Butan-2-one to butan-2-oL .

Q 39.

Phenol can be distinguished from ethanol by the reactions with ………….
(a) Br2/water (b) Na
(c) Neutral FeCl3 (d) All of these

Q 40.

What happens when benzene diazonium chloride is heated with water?

Q 41.

Explain why is O = C = O nonpolar while R – O – R is polar.

Q 42.

In Kolbe's reaction, instead of phenol, phenoxide ion is treated with carbon dioxide. Why?

Q 43.

Explain why is p-nitrophenol more acidic than phenol?

Q 44.

Match the items of Column I with items of Column II.ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-52
 

Q 45.

Assertion (A): Ethanol is a weaker acid than phenol.
Reason (R): Sodium ethoxide may be prepared by the reaction of ethanol with aqueous NaOH.

Q 46.

Write the mechanism of the reaction of HI with methoxybenzene.

Q 47.

Give structures of the products you would expect when each of the following alcohol reacts with (a)HCl-ZnCl2 (b)HBrand (c) SOCl2
(i)Butan-1-ol
(ii)2-Methylbutan-2-ol

Q 48.

(i) Draw the structures of all isomeric alcohols of molecular formula C5HI20 and give their IUPAC names.
(ii) Classify the isomers of alcohols in question (i)as primary, secondary and tertiary alcohols.

Q 49.

Write the equation of the reaction of hydrogen iodide with (i)1-propoxypropane (ii)methoxybenzene, and (iii)benzyl ethyl ether

Q 50.

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.