Question Set D

cbse 12th Standard Chemistry Alcohols , Phenols and Ethers Important Questions And Answers Study Material - QB365

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Questions:

Generic 2

4 x 2 = 8

Give the structures A, B and C in the following reaction.

Name the compound with molecular formula C₇H₈O which on treatment with Br₂ water, readily gives a precipitate of C₇H₅OBr_3.

Name reagents required for preparation of methyl orange indicator (no reaction).

(i) CH₃CH₂I \(\overset { NaCN }{ \longrightarrow } \ ?\ \overset { OH^{ - },\ partial\ hydrolysis }{ \longrightarrow } \)?
(ii) CH₃CH₂Br

Multiple Choice Question

10 x 1 = 10

Phenol does not undergo nucleophilic substitution reaction easily due to

(a)

acidic nature of phenol

(b)

partial double bond character of C-OH bond

(c)

partial double bond character of C-C bond

(d)

instability of phenoxide ion

C', Product 'C' is

(a)

(b)

(c)

(d)

Find the product of the given reaction:

(a)

(b)

(c)

(d)

'X', X is

(a)

(b)

(c)

(d)

Which of the following amine will form stable diazonium salt at 273-278K?

(a)

C₂H₅NH₂

(b)

C₆H₅NH₂

(c)

C₆H₅CH₂NH₂

(d)

C₆H₅N(CH₃)₂

10.

What would be the side products formed with primary amine in the Hofmann bromamide degradation reaction?

(a)

Na₂CO₃ + NaBr

(b)

NaBr + H₂O + NaOH

(c)

NaBr + H₂O + Na₂CO₃

(d)

Br₂ + H₂O + Na₂CO₃

11.

Carbon-halogen bond is polarised because

(a)

halogen atom is less electronegative

(b)

halogen atom is more electronegative than carbon atom

(c)

carbon bears negative charge while halogen bears positive charge

(d)

None of the above

12.

The position of Br in the compound CH₃CH= CHC(Br)(CH₃)₂ can be classified as ___________.

(a)

allyl

(b)

aryl

(c)

vinyl

(d)

secondary

13.

Iodoform can be prepared from all except

(a)

isopropyl alcohol

(b)

3-methyl-2-butanone

(c)

isobutyl alcohol

(d)

ethyl methyl ketone

14.

Nitration of nitrobonzene results in..............

(a)

o-dinitrobenzene

(b)

1, 3, 5-trinitrobenzene

(c)

p-dinitrobenzene

(d)

m-dinitrobenzene

Generic 5

4 x 5 = 20

15.

(i) What happens when
(a) phenol reacts with bromine water?
(b) ethanol reacts with CH₃COCl/pyridine?
(c) anisole reacts with HI?
Write the chemical equations involved in the above reactions.
(ii) Distinguish between
(a) Ethanol and phenol
(b) Propan-2-ol and 2-methylpropan-2-o1

16.

An alkyl halide (A) of molecular formula, C₆H₁₃Cl on treatment with alcoholic KOH gives two isomeric alkenes (B) and (C) of molecular formula, C₆H₁₂- Both alkenes on hydrogenation gives 2, 3-dimethylbutane. Write the structures of (A), (B) and (C).

17.

Write equation of the following reactions.
(i) Friedel-Crafts reaction (alkylation in anisole)
(ii) Nitration of anisole
(iii) Bromination of anisole in ethanoic acid medium
(iv) Friedel-Crafts (acetylation of anisole)

18.

(i) tert-Butylamine cannot be prepared by the action of NH₃ on tert-butyl bromide. Explain why?
(ii) Suggest a convenient method for the preparation of tert-butylamine.

Generic 3

3 x 3 = 9

19.

What happens when
(i) salicylic acid is treated with (CH₃CO)₂O/H⁺?
(ii) anisole is treated with CH₃Cl/ anhyd. AlCl₃?
Write chemical equation in support of your answer.

20.

Why p-dibromobenzene has higher melting point than those of ortho- and meta- isomers?

21.

Write the structures of A, Band C in the following:
(i) C₆H₅-CONH₂
(i) \({ CH }_{ 3 }-CI\overset { KCN }{ \longrightarrow } A\overset { { LiAIH }_{ 4 } }{ \longrightarrow } b\overset { { CHCI }_{ 3 }+alc.KOH }{ \longrightarrow } C.\)

Case Study Questions

2 x 4 = 8

22.

Read the passage given below and answer the following questions:
A compound (X) containing C, Hand O is unreactive towards sodium. It also does not react with Schiff's reagent. On refluxing with an excess ofhydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The compound (X) is an

(a) acid

(b) aldehyde

(c) alcohol

(d) ether

(ii) The IUPAC name of the acid formed is

(a) methanoic acid

(b) ethanoic acid

(c) propanoic acid

(d) butanoic acid.

(iii) Compound (Y) is

(a) ethyl iodide

(b) methyl iodide

(c) propyl iodide

(d) mixture of (a) and (b).

(iv) Compound (X) on treatment with excess of Cl₂ in presence of light gives

(a) \(\alpha\) - chlorodiethyl ether

(b) \(\alpha\), \(\alpha\)' -dichlorodiethyl ether

(c) perchlorodiethyl ether

(d) none of these.

23.

Read the passage given below and answer the following questions:
Consider the given sequence of reactions:
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Identify w.

(ii) When X reacts with CH₃COCI in presence of anhy. AICI₃, the reaction is known as

(a) Fittig reaction

(b) Ullmann reaction

(c) Wurtz-Fittig reaction

(d) Friedel-Crafts acylation reaction.

(iii) When X is treated Ni-Al / NaOH the product obtained is

(a) benzene

(b) phenol

(c) p-chlorophenol

(d) triphenyl.

(iv) Compound Z is

(a) phenol

(b) p-chlorophenol

(c) p-nitrophenol

(d) nitrobenzene

Assertion and reason

5 x 1 = 5

24.

Assertion: Vinyl chloride is less reactive than alkyl chloride.
Reason: Stability of alkyl halide decreases as the strength of C-X bond decreases.
Codes:
A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C) Assertion is correct statement but reason is wrong statement.
D) Assertion is wrong statement but reason is correct statement.

25.

Assertion : The bond angle in alcohols is slightly less than the tetrahedral angle.
Reason : In alcohols, the oxygen of –OH group is attached to sp3 hybridized carbon atom.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

26.

Assertion : CCl₄ is not a fire extinguisher.
Reason : CCl₄ is insoluble in water.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

27.

Assertion: In Hoffmann bromamide reaction, the amine formed has one carbon atom less than the parent 1°amide.
Reason: N-methyl acetamide undergoes Hoffmann bromamide reaction.
Codes:
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

28.

Assertion: Phenol decomposes NaHCO₃ solution to evolve CO₂ gas.
Reason: Picric acid is 2, 4, 6-trinitrophenol.
Codes:
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

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Answers Key:

Generic 2

4 x 2 = 8

C₆H₅CH₂OH

Reagents required are:
(i) sulphanilic acid
(ii) N, N-dimethylaniline
(iii) NaNO₂ HCI and
(iv) a base.

(i) CH₃CH₂CN, CH₃CH₂CONH₂
(ii) CH₃CH₂CN, CH₃CH₂CH₂NH₂

Multiple Choice Question

10 x 1 = 10

(b)
partial double bond character of C-OH bond

(b)
C₆H₅NH₂

10.

11.

(b)
halogen atom is more electronegative than carbon atom

12.

(a)
allyl

13.

14.

(d)
m-dinitrobenzene

Generic 5

4 x 5 = 20

15.

(ii) (a) Phenol gives violet colouration with FeCl₃, solution but ethanol does not.

(b) Propan-2-ol when warmed with l₂, in NaOHg ives yellow precipitate of iodoform, while 2-methylpropan-2-ol does not respond to this test.

16.

The reaction takes place as follows

17.

18.

(i) tert-Butyl bromide being a 3° alkyl halide on treatment with a base (i.e. NH₃) prefers to undergo elimination rather than substitution. Therefore, the product is isobutylene rather than tert-butylamine.

1° amines containing tert-alkyl groups can be prepared by action of suitable Grignard reagents on O-methylhydroxylarnine. For example,

Generic 3

3 x 3 = 9

19.

(i)

(ii)

20.

p-dibromobenzene has higher melting point than its o-isomer due to symmetry of p-isomer that fits in the crystal lattice better than the o-isomer.
Hence, p-isomer has higher melting point than o-isomer (or m-isomer).

21.

(i) \({ C }_{ 6 }{ H }_{ 5 }-{ CONH }_{ 2 }\overset { { Br }_{ 2 }/KOH }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }{ NH }_{ 2 }\)
\([A]\overset { { NaNO }_{ 2 }+HCI }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }{ N }_{ 2 }^{ + }{ CI }^{ - }[B]\overset { KI }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }I[C]\)
(ii) \({ CH }_{ 3 }CI\overset { KCN }{ \longrightarrow } { CH }_{ 3 }CN[A]\overset { { LiAIH }_{ 4 } }{ \longrightarrow } { CH }_{ 3 }{ CH }_{ 2 }{ NH }_{ 2 }[B]\overset { { CHCI }_{ 3 }+KOH }{ \longrightarrow } { CH }_{ 3 }{ CH }_{ 2 }NC[C]\)

Case Study Questions

2 x 4 = 8

22.

(i) (d): Since the compound X is unreactive towards sodium so it is neither an acid nor an alcohol. Since the compound X is unreactive towards Schiff's base so it is not an aldehyde.
The compound X forms only one product on reaction with excess HI, indicates that the compound X may be ether.
(ii) (b): The reactions can be written as :

Since the equivalent weight of carboxylic acid is 60. So, it must be CH₃COOH i.e., ethanoic acid.
(iii) (a) : The alcohol Z in that case should be C₂H₅OH and the compound Y should be ethyl iodide.
X is therefore diethyl ether (C₂H₅ - O -C₂H₅)

(iv) (C): In the presence of light and excess of chlorine, all the hydrogen atoms of diethyl ether are substituted to give perchlorodiethyl ether.
\( \mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{3}+10 \mathrm{Cl}_{2} \stackrel{\mathrm{h} \mathrm{v}}{\longrightarrow}\\ \quad\quad\quad \quad \quad \quad \quad \quad \quad \quad \quad { (excess) } \) \( \mathrm{CCl}_{3} \mathrm{CCl}_{2}-\mathrm{O}-\mathrm{CCl}_{2}-\mathrm{CCl}_{3}+10 \mathrm{HCl}\\ \text { Perchlorodiethyl ether } \)

23.

Assertion and reason

5 x 1 = 5

24.

B) Assertion and reason both are correct statements but reason is not correct explanation for assertion

25.

(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

26.

(d) If both the Assertion and Reason are incorrect.
Explanation:
CCl₄ is used as a fire extinguisher. The dense, non combustible vapours cover the burning substance and prevents the availability of oxygen around burning material.

27.

(c): Only primary amines can be prepared from amides (RCONH₂ ) by treating with Br₂ and KOH. Thus, N-methyl acetamide i.e., CH₃CONHCH₃ does not undergo Hoffmann bromamide reaction.

28.

(d): Phenol is a weaker acid than carbonic acid and hence, does not decompose NaHCO₃ solution to evolve CO₂ gas. Picric acid is 2, 4, 6-trinitrophenol.