Chemistry

Alcohols, Phenols and Ethers

Question:

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

Answer:


ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-13
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-25

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Alcohols, Phenols and Ethers

Q 1.

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

Q 2.

The carbon-oxygen bond in phenol is slightly stronger than that in methanol. Why?

Q 3.

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

Q 4.

What happens when benzene diazonium chloride is heated with water?

Q 5.

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

Q 6.

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

Q 7.

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

Q 8.

Arrange the following compounds in decreasing order of acidity:
H2O, R-OH, HC = CH

Q 9.

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

Q 10.

When phenol is treated with bromine water, white precipitate is obtained. Give the structure and the name of the compound formed.

Q 11.

Explain why is OH group in phenols more strongly held as compared to OH group in alcohols.

Q 12.

Explain why is p-nitrophenol more acidic than phenol?

Q 13.

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 14.

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

Q 15.

Explain why are low molecular mass alcohols soluble in water?

Q 16.

Show how would you synthesise the following alcohols from appropriate alkanes?
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-42

Q 17.

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

Q 18.

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

Q 19.

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 20.

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 21.

Identify aliylic alcohols in the above examples.

Q 22.

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

Q 23.

Write the IUPAC name of the compound given below.
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-25

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.

What is the correct order of reactivity of alcohols in the following reaction?
ncert-exemplar-problems-class-12-chemistry-alcohols-phenols-ethers-3

Q 26.

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 27.

Write the mechanism of the reaction of HI with methoxymethane.

Q 28.

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 29.

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

Q 30.

Assertion (A): Phenol forms 2,4, 6-tribromophenol on treatment with Br2 in carbon disulphide at 273 K.
Reason (R): Bromine polarizes in carbon disulphide.

Q 31.

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

Q 32.

Write the structures of the isomers of alcohols with molecular formula C4H10O. Which one of these isomers exhibits optical activity?

Q 33.

Nitration is an example of aromatic electrophilic substitution and its rate depends upon the group already present in the benzene ring. Out of benzene and phenol, which one is more easily nitrated and why?

Q 34.

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 35.

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

Q 36.

Out of 2-chloroethanol and ethanol which is more acidic and why?

Q 37.

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

Q 38.

Arrange water, ethanol and, phenol in increasing order of acidity and give reason for your answer.

Q 39.

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 40.

Write the mechanism of the reaction of HI with methoxybenzene.

Q 41.

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

Q 42.

Write chemical reaction for the preparation of phenol from chlorobenzene.

Q 43.

You are given benzene, cone. H2S04and NaOH. Write the equations for the preparation of phenol using these reagents.

Q 44.

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 45.

When 3-methylbutant 2-ol is treated with HBr, the following reaction takes place:
ncert-solutions-for-class-12-chemistry-alcohols-phenols-and-ether-47
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.)

Q 46.

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

Q 47.

What is the structure and IUPAC name of glycerol?

Q 48.

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

Q 49.

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

Q 50.

Dipole moment of phenol is smaller than that of methanol. Why?