2nd PUC Chemistry Question Bank Chapter 13 Amines

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Karnataka 2nd PUC Chemistry Question Bank Chapter 13 Amines

Question 1.
Give the IUPAC names for the following amines.
Answer:

Question 2.
How nitro compounds are converted into amines? Give examples.
Answer:
Nitro compounds are reduced to amines by passing hydrogen gas in the presence of finely divided nickel, palladium or platinum catalyst.

Question 3.
How nitriles are converted into primary amines?
Answer:
Nitriles on reduction with LiAlH₄ or catalytic hydrogenation produce primary amines.

Question 4.
How amides are converted into amines?
Answer:
Amides on reduction with LiAIH₄ gives amines.

Question 5.
Explain Hoffmann bromamide degradation reaction.
Answer:
Amide on reaction with bromine in an aqueous sodium hydroxide. Primary amine is obtained.
R – CO – NH₂ + Br₂ + 4NaOH → R – NH₂ + 2NaRr + 2H₂O + Na₂CO₃

Question 6.
Explain Hoffmann bromamide degradation for the preparation of Imethanamine.
Answer:
When ethanamide (acetamide) is treated with bromine in aqueous solution of sodium hydroxide, methanamine is obtained.
CH₃CONH₂ + Br₂ + 4NaOH → CH₃NH₂ + 2NaBr + 2H₂O + Na₂CO₃

Question 7.
Explain Hoffmann bromamide degradation for the preparation of aniline.
Answer:
When benzenamide is treated with bromine in aqueous solution of sodium hydroxide aniline is obtained.

Question 8.
Explain carbylamine reaction.
Answer:
Primary amines on heating with chloroform and alcoholic KOH form carbylamines.

Question 9.
How is aniline converted in phenyl isocyanide? Write the equation.
Answer:
Aniline on heating with chloroform and alcoholic potassium hydroxide forms phenyl isocyanide.

Question 10.
How primary aliphatic amine reacts with nitrous acid?
Answer:
Primary aliphatic amine reacts with nitrous acid to form respective alcohol liberating nitrogen gas.
R – NH₂ + HNO₂ → R – OH + N₂ + HCl

Question 11.
How aromatic primary amine reacts with nitrous acid?
Answer:
Aromatic primary amine react with nitrous acid (NaNO₂ + HCl) at low temperature (273K) to form benzene diazonium chloride.

Question 12.
Complete the following reactions.

Answer:

Question 13.
What is Hinsberg’s reagent?
Answer:
Benzene sulphonyl chloride (C₆H₅SO₂Cl) is called Hinsberg’s reagent.

Question 14.
What is Hinsberg’s reagent? How it is used to distinguish primary amine from a secondary amine?
Answer:
Benzene sulphonyl chloride (C₆H₅SO₂Cl) is called Hinsberg’s reagent. Primary amine reacts with Hinsberg’s reagent to form a product soluble in an alkali. Secondary amine reacts with Hinsberg’s reagent to form a product insoluble in an alkali.

Question 15.
How aniline reacts with bromine water?
Answer:
Aniline reacts with bromine water at room temperature to give a white ppt of 2,4,6-tribromophenol.

Question 16.
What is the action of bromine water on benzanamine (aniline) at room temperature?
Answer:
Aniline reacts with bromine water at room temperature to give a white ppt of 2,4,6-tribromophenol.

Question 17.
Write the IUPAC name of the product formed when aniline reacts with bromine water.
Answer:
2,4,6-Tribromophenol.

Question 18.

Answer:
X → Aniline.
Y → 2,4,6-tribromophenol.

Question 19.
How aniline reacts with Cone. H₂SO₄.
Answer:
Aniline reacts with Cone. H₂SO₄ at 453K-473K to produce p-aminobenzene sulphonic acid (sulphanilic acid).

Question 20.
What is diazotisation reaction? Give example.
Answer:
The conversion of primary aromatic amines into diazonium salts is known as diazotisation.

Question 21.
Explain Sandmeyer reaction.
Answer:
When benzene diazonium salts are treated with cuprous chloride in hydrochloric acid chlorobenze is obtained.

Question 22.
Explain Guttermann reaction.
Answer:
When benzene diazonium chloride solution treated with hydrochloric acid in presence of copper powder chlorobenzene is obtained.

Question 23.
How benezene diazonium chloride is converted into flurobenzene?
Answer:
When benzene diazonium chloride is heated with fluroboric acid flurobenzene is obtained.

Question 24.
Howbenzene diazonium chlöì4de is cõnei1 ed into phenol?
Answer:
When benzene diazonium chloride solution is heated at 283K phenol is obtained.

Question 25.
Between CH₃NH₂ and C₆H₅NH₂ which is more basic.
Answer:
Methylamine.

Question 26.
What are P and Q? Name the reaction occuring in step 1.

Answer:
P = CH₃NH₂ (Methanamine),
Q = CH₃OH (Methyl alcohol)
Step – 1 reaction is Hoffmann bromide degradation reaction.

Question 27.
Identify the reactant A in the following reaction. A + 2R-X → R₄N⁺X^–
Answer:
R₂NH

Question 28.
Which is more basic among aqueous solutions of aniline and ammonia? Give one reason?
Answer:
Ammonia is more basic than aniline. The lone pair of electrons on nitrogen atom of aniline are involved in resonance with benezene ring, hence electrons MIV not easily available for donation, compared to ammonia.

Question 29.
Which is more basic among methylamine and aniline?
Answer:
Methylamine.

Question 30.
Name the major organic product formed in the following conversion.
1. When nitrous acid is treated with methylamine.
2. Benzene diazonium chloride is treated with Kl.
Answer:
1. Methyl alcohol
2. Iodobenzene.

Question 31.
What is acylation? Give example.
Answer:
Most of amines react with acid chlorides, anhydrides and esters by nucleophillic substitution reaction. This reaction is known as acylation.

Question 32.
Arrange the following in the increasing order of their strengths in the aqueous medium. (CH₃N)₃ CH₃NH₂ (CH₃)₂NH. Give one reason for the trend observed.
Answer:
(CH₃)₂NH > CH₃NH₂ > (CH₃)₃N
Steric hinderence or Solvation effect.

Question 33.
Explain the trend in base strengths of 1°,2°,3° methyl amines in gaseous phase.
Answer:
The trend 3° > 2° > 1° for the base strengths of amines. This is due to increase in +1 effect of alkyl groups.

Question 34.
Name the major product obtained when nitrous acid is treated with
1. Methylamine
2. Aniline at low temperature.
Answer:
1. Methyl alochol
2. Benzene diazonium chloride.

Question 35.
The pK_b values of ammonia, methanamine and benzenamine (aniline) are 4.75, 3.38, 9.38 respectively. Arrange them in the increasing order of their basic strength.
Answer:
Benzenamine < Ammonia < Methanamine.

Question 36.
Why aromatic primary amines cannot be prepared by Gabrial synthesis.
Answer:
Because arylhalides cannot undergo nucleophilic substitution reaction with ion formed by phthalamide.