Question Set A

cbse 12th Standard Chemistry Amines Important Questions And Answers Study Material - QB365

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Questions:

Generic 2

5 x 2 = 10

Arrange the following compounds in increasing order of solubility in water:
C₆H₅NH₂, (C₂H₅ )₂NH, C₂H₅NH₂

Identify A and B in the following reactions.
\(\begin{equation} \text { (i) } \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{C} \equiv \mathrm{N} \stackrel{\mathrm{LiAlH}_{4}}{\longrightarrow} A \stackrel{\mathrm{HNO}_{2}}{\longrightarrow} B \end{equation}\)

(i) Tert-butylamine cannot be prepared by the action of NH₃ on tert-butylbromide. Give reason.
(ii) How is aminomethane obtained from ethanal?

Give a chemical test to distinguish between a primary and a secondary amine.

How will you carry out the following conversions?
(i) toluene \(\longrightarrow \) p-toluidine
(ii) p-toluidine diazonium chloride \(\longrightarrow \) p-toluic acid

Generic 3

5 x 3 = 15

(a) Account for the following:
(i) Aniline is weaker base than cyclohexylamine.
(ii) Silver chloride dissolves in CH₃NH₂solution .
(b) Arrange the following compounds in increasing order of basic strength in aqueous solution:
NH₃ , RNH₂ , R₂NH, R₃N (R is CH₃ )

Write the chemical equations involved when C₂H₅NH₂is treated with the following reagents:
(i) CH₃COCI/pyridine
(ii) C₆H₅SO₂CI
(iii) CHCl₃ + KOH

Arrange the following in increasing order of this basic strength:
(a) C₂H₅NH₂, C₆H₅NH₂, NH₃, C₆H₅CH₂NH₂ and (C₂H₅)₂ NH
(b) C₂H₅NH₂, (C₂H)₂NH, (C₂H₅)₃N, C₆H₅NH₂
(c) CH₃NH₂, (CH₃)₂NH, (CH₃)₃N, C₆H₅NH₂, C₆H₅CH₂NH₂

Identify the compounds A, B and C in the following reactions:

10.

An organic compound 'A' having molecular formula C₃H₅N on hydrolysis gave another compound 'B' The compound 'B' on treatment with CHCI9₃ and alcoholic caustic potash gave an offensive smelling substance 'C' . Identify 'A' , 'B' and 'C'.

Generic 5

3 x 5 = 15

11.

Write short notes on the following.
(i) Hofmann bromamide reaction
(ii) Ammonolysis
(iii) Gabriel phthalimide synthesis

12.

An aromatic compound 'A' of molecular formula C₇H₇ON undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions.

13.

A hydrocarbon 'A' (C₄H₈) on reaction with HCI gives a compound 'B' , (C₄H₁₁N). On reacting with NaNO₂ and HCI followed by treatment with water, compound 'C'. Ozonolysis of 'A' gives 2 moles of acetaldehyde. Identify compounds 'A' to 'D' . Explain the reactions involved.

Multiple Choice Question

12 x 1 = 12

14.

Which of the following cannot be prepared by Sandmeyer's reaction?

(a)

Chlorobenzene

(b)

Bromobenzene

(c)

lodobenzene

(d)

Fluorobenzene

15.

Among (CH₃)₃N and CH₃CN, the electro negativity in the order

(a)

(b)

(c)

(d)

all have same

16.

C', Product 'C' is

(a)

(b)

(c)

(d)

17.

Which of the following reagent is required for the following conversion?

(a)

CH₃NH₂CH₃CI

(b)

CH₃CI,RNH₂

(c)

NH₃, CH₃CI

(d)

CH₃CH₂NH₂

18.

p-Chloroaniline and anilinium hydrochloride can be distinguished by

(a)

Sandmeyer reaction

(b)

NaHCO₃ solution

(c)

AgNO₃ solution

(d)

Carbylamine reaction

19.

Which of the following will be the most stable diazonium salt, \({ RN }_{ 2 }^{ + }{ X }^{ - }\) ?

(a)

\(CH_{ 3 }{ N }_{ 2 }^{ + }{ X }^{ - }\)

(b)

\({ C }_{ 6 }H_{ 5 }{ N }_{ 2 }^{ + }{ X }^{ - }\)

(c)

\(CH_{ 3 }{ CH }_{ 2 }{ N }_{ 2 }^{ + }{ X }^{ - }\)

(d)

\({ C }_{ 6 }H_{ 5 }{ CH }_{ 2 }{ N }_{ 2 }^{ + }{ X }^{ - }\)

20.

Which of the following compounds will dissolved in an alkali solution after it undergoes reaction with Hinsberg's reagent?

(a)

CH₃NH₂

(b)

(CH₃)₃N

(c)

(C₂H₅)₂NH

(d)

C₆H5NHC₆H₅

21.

Nitrobenzene on reaction with conc.HNO₃/H₂SO₄ at 80-\({ 100 }^{ \circ }\)C forms which one of the following products?

(a)

1, 4-Dinitrobenzene

(b)

1, 2, 4-Trinitrobenzene

(c)

1,2-Dinitrobenzene

(d)

1, 3-Dinitrobenzene

22.

Methylamine reacts with NHO₂ to form...................................... .

(a)

CH₃-O-N=O

(b)

CH₃-O-CH₃

(c)

CH₃OH

(d)

CH₃CHO

23.

Ethylamine on heating with CS₂ in presence of HgCl₂ forms

(a)

\({ C }_{ 2 }{ H }_{ 5 }NCS\)

(b)

\(\left( { C }_{ 2 }{ H }_{ 5 } \right) _{ 2 }S\)

(c)

\(\left( { C }_{ 2 }{ H }_{ 5 } \right) _{ 2 }CS\)

(d)

\({ C }_{ 2 }{ H }_{ 5 }\left( CS \right) _{ 2 }\)

24.

The amine that reacts with NaNO₂+ HCI to give yellow oily liquid is

(a)

ethylamine

(b)

diethylamine

(c)

isopropylamine

(d)

secondary but ylamine

25.

When a primary amine reacts with chloroform and ethanolic KOH, then the product formed is

(a)

isocyanide

(b)

aldehyde

(c)

cyanide

(d)

alcohol

Assertion and reason

10 x 1 = 10

26.

Assertion : Nitrating mixture used for carrying out nitration of benzene consists of conc. HNO₃⁺ conc. H₂SO₄
Reason : In presence of H₂SO₄, HNO₃ acts as a base and produces NO₂⁺ ions.
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 : Acetanilide is less basic than aniline.
Reason : Acetylation of aniline results in decrease of electron density on nitrogen.
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.

28.

Assertion : Amines are basic in nature.
Reason : Amines have lone pair of electrons on nitrogen 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.

29.

Assertion : Aromatic 1°amines can be prepared by Gabriel phthalimide synthesis.
Reason : Aryl halides undergo nucleophilic substitution with anion formed by phthalimide.
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.

30.

Assertion: Ortho substituted anilines are usually weaker bases than anilines.
Reason: This is due to ortho effect.
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.

31.

Assertion: Me₃N reacts with BF₃whereas Ph₃N does not.
Reason: The electron pair on nitrogen atom in Ph₃N is delocalised in the benzene ring and is not available for boron in BF_3.
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.

32.

Assertion: Ammonia is more basic than water.
Reason: Nitrogen is less electronegative than oxygen.
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.

33.

Assertion: Aniline is a weaker base than cyclohexylamine.
Reason: Aniline undergoes halogenation even in the absence of a catalyst.
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.

34.

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.

35.

In the following questions. an Assertion (A) is followed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) Hofmann's bromamide reaction is given by primary amines.
Reason (R) Primary amines are less basic than secondary amines.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

Case Study Questions

2 x 4 = 8

36.

Observe the histogram showing boiling points of pentane, iso pentane, 1°,2° and 3 ° amines. Answer the questions that follow based on table and related concepts.

(a) Why does CH₃CH₂CH₂CH₂NH₂(1° amine) has higher boiling point than (C₂H₅)₂NH and C₂H₅N(CH₃ )₂?
(b) Why does ethanol have higher boiling point than ethanamine?
(c) Why amines are more basic than alcohol?
(d) Why are Primary amines more soluble in water than 2° and 3° amines?
(e) Arrange the compounds shown in graph, increasing order of boiling points. Give reason.

37.

Read the passage given below and answer the following questions:
Amines are produced when an alcoholic solution of ammonia and an alkyl or a benzyl halide is heated in a sealed tube at 373 K. This reaction is called ammonolysis and usually gives a mixture of primary, secondary and tertiary amines along with some quarternary ammonium salts. This reaction is an example of nucleophilic substitution reaction in which ammonia acts as a nucleophile due to the presence of a lone pair of electrons on the nitrogen atom. However this method cannot be used for the preparation of aryl amines. One of the most convenient methods for the preparation of aryl amines is reduction of nitro compounds. Aryl amines can also be prepared by reduction of nitrites or Gabriel phthalimide synthesis.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(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. .
(i) Assertion: Ammonolysis of alkyl halides only produces 2^o amines.
Reason: Ammonolysis of alkyl halides involves the reaction between alkyl halides and alcoholic ammonia.
(ii) Assertion: Ammonolysis method cannot be used for the preparation of aryl amines.
Reason: Aryl halides are much less reactive than alkyl halides towards nucleophilic substitution reaction.
(iii) Assertion: Ammonolysis can be used to prepare pure primary amines.
Reason: Ammonolysis of haloalkanes lead to multiple ammonium salts.
(iv) Assertion: Aromatic 1^p amines can not be prepared by Gabriel phthalimide synthesis.
Reason: Aryl halides do not undergo nucleophilic substitution with anion formed by phthalimide.

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Answers Key:

Generic 2

5 x 2 = 10

C₆H₅NH₂ < (C₂H₅)₂NH < C₂H₅NH₂ is the increasing order of solubility in water.

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.

Carbylamine reaction or Libermann nitroso reaction.

Generic 3

5 x 3 = 15

(a) (i) It is due to resonance in aniline, lone pair is delocalised but in cyclohexylamine, it is readily available.
(ii) It is due to the formation of soluble complex.
\(\mathrm{AgCl}+2 \mathrm{CH}_{3} \mathrm{NH}_{2} \longrightarrow\left[\mathrm{Ag}\left(\mathrm{CH}_{3} \mathrm{NH}_{2}\right)_{2}\right]^{+} \mathrm{Cl}^{-}\)
(b) NH₃ < R₃N < RNH₂< R₂NH.

\(\text { (i) } \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}+\mathrm{CH}_{3} \mathrm{COCl} \stackrel{\text { Pyridine }}{\longrightarrow} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NHCOCH}_{3}+\mathrm{HCl}\)
\( \text { (ii) } \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}+\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{2} \mathrm{Cl} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{2} \mathrm{NHC}_{2} \mathrm{H}_{5}+\mathrm{HCl} \)
\(\text { (iii) } \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}+\mathrm{CHCl}_{3}+3 \mathrm{KOH} \longrightarrow \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{~N} \equiv \mathrm{C}+3 \mathrm{KCl}+3 \mathrm{H}_{2} \mathrm{O} \)

10.

Generic 5

3 x 5 = 15

11.

(i) Hoffmann bromamide reaction
When an amide is treated with bromine in an aqueous or ethanolic solution of sodium hydroxide, a primary amine with one carbon atom less than the original amide is produced. This degradation reaction is known as Hoffmann bromamide reaction. This reaction involves the migration of an alkyl or aryl group from the carbonyl carbon atom of the amide to the nitrogen atom.

(ii) Ammonolysis
When an alkyl or benzyl halide is allowed to react with an ethanolic solution of ammonia, it undergoes nucleophilic substitution reaction in which the halogen atom is replaced by an amino (−NH₂) group. This process of cleavage of the carbon-halogen bond is known as ammonolysis.

When this substituted ammonium salt is treated with a strong base such as sodium hydroxide, amine is obtained.
\(\mathrm{R}-\stackrel{+}{\mathrm{N}} \mathrm{H}_3 \stackrel{-}{\mathrm{X}}+\mathrm{NaOH} \longrightarrow \mathrm{R}-\mathrm{NH}_2+\mathrm{H}_2 \mathrm{O}+\mathrm{NaX}\)
Amine
Though primary amine is produced as the major product, this process produces a mixture of primary, secondary and tertiary amines, and also a quaternary ammonium salt as shown.

(iii) Gabriel phthalimide synthesis
Gabriel phthalimide synthesis is a very useful method for the preparation of aliphatic primary amines. It involves the treatment of phthalimide with ethanolic potassium hydroxide to form potassium salt of phthalimide. This salt is further heated with alkyl halide, followed by alkaline hydrolysis to yield the corresponding primary amine.

12.

13.

Multiple Choice Question

12 x 1 = 12

14.

15.

16.

17.

(a)
CH₃NH₂CH₃CI

18.

Both p-chloroaniline and anilinium hydrochloride are \({ 1 }^{ \circ }\) amines and hence cannot be ditinguished by carbylamine reaction.

19.

Due to delocalization of the +ve charge on the benzene ring, aromatic diazonium salts are more satble, i.e., option (b) is correct.

20.

Amines form benzenesulphonamides which are soluble in alkali, i.e., option (a) is correct.

21.

-NO₂ is a m-directing group and hance 1, 3-dinitrobenzene is formed.

22.

23.

(a)
\({ C }_{ 2 }{ H }_{ 5 }NCS\)

24.

amines, i.e., diethylamine reacts with NaNO₂+HCI to give yellow oily nitrosoamine.

25.

Carbylamine reaction yields isocyanides.

Assertion and reason

10 x 1 = 10

26.

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

27.

(d) If both the Assertion and Reason are incorrect.

28.

(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
Explanation:
Amines are basic due to the presence of a lone pair of electrons on nitrogen atom. The lone pair can be easily donated.

29.

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

30.

(a): Ortho effect is a consequence of steric and electronic factors.

31.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

32.

(a): Ammonia is more basic than water. It is because nitrogen being less electronegative than oxygen, has a greater tendency to donate electrons

33.

(b): Aniline exists as resonance hybrid. As a result of resonance, the lone pair of electrons on nitrogen gets delocalized over the benzene ring and thus, is less easily available for protonation than in case of cyclohexylamine where no such resonance takes place.

34.

(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.

35.

(d) Hofmann's bromamide reaction is given by amide which on reaction with NaOX produces amine having one carbon less than amide. Hence, (A) is not correct but (R) is correct statement.

Case Study Questions

2 x 4 = 8

36.

(a) It is because extent of H-bonding is more in CH₃CH₂CH₂CH₂NH₂ than 2° and 3° amines.
(b) It is because H-bonds are stronger in alcohols than amines because 'O' is more electronegative than 'N'.
(c) It is because \(\stackrel{\oplus}{\mathrm{RNH}_{3}}\) is more stable than \(\underset{\mathrm{ROH2}}{\oplus}\) . +ve charge on oxygen is not stable.
(d) It is because primary amines can form H-bonds with water to more extent.
(e) C₂H₅CH(CH₃)₂ < CH₃(CH₂)₃CH₃ < C₂H₅N(CH₃)₂ < (C₂H₅)₂NH < C₄H₉NH₂.
Isopentane has lower boiling point that n-Pentane due to branching less surface area, less van der Waals' forces of attraction. 3° < 2° < 1° is order of boiling point in amines because extent of H-bonding increases.

37.

(i) (d): Reaction can be used to prepare 1°, 2°, 3° amines and finally quaternary ammonium salts.
(ii) (a)
(iii) (d): Ammonolysis cannot be used to prepare pure primary amines. This method usually gives a mixture of primary, secondary and tertiary amines along with some quaternary ammonium salts.
(iv) (a)