Class 12 Amines Mock Test (CBSE)

Topics in Amines

• Structure of amines
• Classification and nomenclature
• Preparation of amines
• Physical properties
• Basic character of amines
• Chemical reactions of amines
• Method of preparation of diazonium salts
• Chemical reactions of diazonium salts
• Importance of diazonium salts in synthesis

Amines practice questions with answers

1. Q1Multiple choice·1 mark
   Among the isomeric amines of molecular formula $C_3H_9N$, the one with the lowest boiling point is:

   1. (a)Trimethylamine
   2. (b)Propan-2-amine
   3. (c)N-Methylethanamine
   4. (d)Propan-1-amine
   Show answer and step marks

   1. Correct option: (a) Trimethylamine. Tertiary amines do not have intermolecular hydrogen bonding because there are no hydrogen atoms attached to nitrogen, resulting in the lowest boiling point compared to primary and secondary isomeric amines.+1

   Answer: (a)
2. Q2Multiple choice·1 mark
   What is the correct order of basic strength of methylamines in aqueous solution?

   1. (a)$(CH_3)_2NH > (CH_3)_3N > CH_3NH_2$
   2. (b)$(CH_3)_2NH > CH_3NH_2 > (CH_3)_3N$
   3. (c)$CH_3NH_2 > (CH_3)_2NH > (CH_3)_3N$
   4. (d)$(CH_3)_3N > (CH_3)_2NH > CH_3NH_2$
   Show answer and step marks

   1. Correct option: (b) $(CH_3)_2NH > CH_3NH_2 > (CH_3)_3N$. In aqueous solution, the basic strength depends on a combined effect of inductive effect, solvation, and steric hindrance, making secondary amine the strongest base.+1

   Answer: (b)
3. Q3Short answer·2 marks
   Write the chemical equation for the carbylamine reaction of methanamine with chloroform and ethanolic potassium hydroxide. Name the foul-smelling substance formed in the reaction.
   Show answer and step marks

   1. Chemical equation: $\text{CH}_3\text{NH}_2 + \text{CHCl}_3 + 3\text{KOH} \xrightarrow{\Delta} \text{CH}_3\text{NC} + 3\text{KCl} + 3\text{H}_2\text{O}$+1
   2. Name of the foul-smelling product: Methyl isocyanide (or methyl carbylamine)+1

   Answer: $\text{CH}_3\text{NH}_2 + \text{CHCl}_3 + 3\text{KOH} \xrightarrow{\Delta} \text{CH}_3\text{NC} + 3\text{KCl} + 3\text{H}_2\text{O}$; methyl isocyanide (methyl carbylamine).
4. Q4Short answer·2 marks
   Write the chemical equation for the carbylamine reaction of aniline with chloroform and ethanolic potassium hydroxide. Name the major product formed.
   Show answer and step marks

   1. Chemical equation: $\text{C}_6\text{H}_5\text{NH}_2 + \text{CHCl}_3 + 3\text{KOH} \xrightarrow{\Delta} \text{C}_6\text{H}_5\text{NC} + 3\text{KCl} + 3\text{H}_2\text{O}$+1
   2. Major product: phenyl isocyanide (benzene isocyanide or phenyl carbylamine).+1

   Answer: $\text{C}_6\text{H}_5\text{NH}_2 + \text{CHCl}_3 + 3\text{KOH} \xrightarrow{\Delta} \text{C}_6\text{H}_5\text{NC} + 3\text{KCl} + 3\text{H}_2\text{O}$; phenyl isocyanide.
5. Q5Short answer·3 marks
   (a) Write the chemical equation for the preparation of benzene diazonium chloride from aniline. (b) What is the optimum temperature range maintained during this reaction and why is maintaining this low temperature necessary?
   Show answer and step marks

   1. Chemical equation: $\text{C}_6\text{H}_5\text{NH}_2 + \text{NaNO}_2 + 2\text{HCl} \xrightarrow{0-5^\circ\text{C}} \text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{NaCl} + 2\text{H}_2\text{O}$+1.5
   2. Optimum temperature range: $273-278\text{ K}$ ($0^\circ\text{C} - 5^\circ\text{C}$).+0.5
   3. Reason: At higher temperatures, the diazonium salt is unstable and reacts with water to form phenol, releasing nitrogen gas.+1

   Answer: (a) $\text{C}_6\text{H}_5\text{NH}_2 + \text{NaNO}_2 + 2\text{HCl} \rightarrow \text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{NaCl} + 2\text{H}_2\text{O}$. (b) $273-278\text{ K}$ ($0-5^\circ\text{C}$), because the diazonium salt is unstable and at higher temperatures reacts with water to give phenol and nitrogen gas.
6. Q6Short answer·3 marks
   Write the balanced chemical equations involved in the following reactions of benzene diazonium chloride: (i) Reaction with potassium iodide ($\text{KI}$). (ii) Reaction with hypophosphorous acid ($\text{H}_3\text{PO}_2$) in the presence of water. (iii) Sandmeyer reaction using cuprous chloride and $\text{HCl}$.
   Show answer and step marks

   1. (i) $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{KI} \rightarrow \text{C}_6\text{H}_5\text{I} + \text{N}_2 + \text{KCl}$+1
   2. (ii) $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{H}_3\text{PO}_2 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_6 + \text{N}_2 + \text{H}_3\text{PO}_3 + \text{HCl}$+1
   3. (iii) $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- \xrightarrow{\text{Cu}_2\text{Cl}_2/\text{HCl}} \text{C}_6\text{H}_5\text{Cl} + \text{N}_2$+1

   Answer: (i) $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{KI} \rightarrow \text{C}_6\text{H}_5\text{I} + \text{N}_2 + \text{KCl}$ (ii) $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{H}_3\text{PO}_2 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_6 + \text{N}_2 + \text{H}_3\text{PO}_3 + \text{HCl}$ (iii) $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- \xrightarrow{\text{Cu}_2\text{Cl}_2/\text{HCl}} \text{C}_6\text{H}_5\text{Cl} + \text{N}_2$

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