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Amines — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAmines4 Marks
Question
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 373K. 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.
A statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
  1. Assertion and reason both are correct statements and reason is correct explanation for assertion.
  2. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  3. Assertion is correct statement but reason is wrong statement.
  4. Assertion is wrong statement but reason is correct statement.
  1. Assertion: Ammonolysis of alkyl halides only produces 2° amines.
Reason: Ammonolysis of alkyl halides involves the reaction between alkyl halides and alcoholic ammonia.
  1. Assertion: Gabriel-phthalimide reaction can be used to prepare both aryl and alkyl primary amines.
Reason: Aryl halides are more reactive alkyl halides towards nucleophilic substitution reactions.
  1. Assertion: Anunonolysis method cannot be used for the preparation of aryl amines.
Reason: Aryl halides are much less reactive than alkyl halides towards nucleophilic substitution reaction.
  1. Assertion: Ammonolysis can be used to prepare pure primary amines.
Reason: Ammonolysis of haloalkanes lead to multiple ammonium salts.
  1. Assertion: Aromatic 1º amines can not be prepared by Gabriel phthalimide synthesis.
Reason: Aryl halides do not undergo nucleophilic substitution with anion formed by phthalimide.
✓

Answer

  1. (d) Assertion is wrong statement but reason is correct statement.
Explanation:

Reaction can be used to prepare 1º, 2º, 3º amines and finally quaternary ammonium salts.
  1. (c) Assertion is correct statement but reason is wrong statement.
Explanation:

Aryl halides are less reactive than aralkyl halides towards nucleophilic substitution reactions.
  1. (a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
  1. (d) Assertion is wrong statement but reason is correct statement.
Explanation:

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

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