Which of the following reactions will not give a primary amine?
Show Hint
- \( \text{CH}_3\text{CONH}_2 \xrightarrow{\text{Br}_2/\text{KOH}} \)
- \( \text{CH}_3\text{CN} \xrightarrow{\text{LiAlH}_4} \)
- \( \text{CH}_3\text{NC} \xrightarrow{\text{LiAlH}_4} \)
- \( \text{CH}_3\text{CONH}_2 \xrightarrow{\text{LiAlH}_4} \)
The Correct Option is C
Solution and Explanation
(a) Hofmann Bromamide Reaction: \[ \text{CH}_3\text{CONH}_2 \xrightarrow{\text{Br}_2/\text{KOH}} \text{CH}_3\text{NH}_2. \] This reaction involves the conversion of an amide (\( \text{CONH}_2 \)) to a primary amine (\( \text{CH}_3\text{NH}_2 \)) with the loss of one carbon atom.
(b) Reduction of Nitriles: \[ \text{CH}_3\text{CN} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{CH}_2\text{NH}_2. \] Nitriles (\( \text{CN} \)) are reduced to primary amines (\( \text{CH}_3\text{CH}_2\text{NH}_2 \)) using lithium aluminium hydride (\( \text{LiAlH}_4 \)).
(c) Reduction of Isocyanides (Methyl Isocyanide): \[ \text{CH}_3\text{NC} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{NHCH}_3. \] Isocyanides (\( \text{NC} \)) are reduced to secondary amines (\( \text{CH}_3\text{NHCH}_3 \)) using lithium aluminium hydride. Hence, this reaction does not produce a primary amine.
(d) Reduction of Amides: \[ \text{CH}_3\text{CONH}_2 \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{CH}_2\text{NH}_2. \] Amides (\( \text{CONH}_2 \)) are reduced to primary amines (\( \text{CH}_3\text{CH}_2\text{NH}_2 \)) using lithium aluminium hydride. Conclusion: Among the given reactions, option (3) does not produce a primary amine; it produces a secondary amine instead. Final Answer: \[ \boxed{\text{CH}_3\text{NC} \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{NHCH}_3 \text{ (Secondary Amine)}}. \]
Top Questions on Amines
- Identify correct statements: (A) Primary amines do not give diazonium salts when treated with \({NaNO}_2\) in acidic condition.
(B) Aliphatic and aromatic primary amines on heating with \({CHCl}_3\) and ethanolic \({KOH}\) form carbylamines.
(C) Secondary and tertiary amines also give carbylamine test.
(D) Benzenesulfonyl chloride is known as Hinsberg’s reagent.
(E) Tertiary amines react with benzenesulfonyl chloride very easily.
Choose the correct answer from the options given below: Amines have a lone pair of electrons on the nitrogen atom, due to which they behave as Lewis bases. Greater the value of \( K_b \) or smaller the value of \( pK_b \), stronger is the base. Amines are more basic than alcohols, ethers, esters, etc. The basic character of aliphatic amines should increase with the increase of alkyl substitution. However, it does not occur in a regular manner, as a secondary aliphatic amine is unexpectedly more basic than a tertiary amine in aqueous solutions. Aromatic amines are weaker bases than ammonia and aliphatic amines. Electron-releasing groups such as \( -CH_3 \), \( -NH_2 \), etc., increase the basicity, while electron-withdrawing substituents such as \( -NO_2 \), \( -CN \), halogens, etc., decrease the basicity of amines. The effect of these substituents is more pronounced at the para-position than at the meta-position.
(a) Arrange the following in increasing order of their basic character. Give reason:
\[ \includegraphics[width=0.5\linewidth]{ch29i.png} \]- Amines have a lone pair of electrons on nitrogen atom due to which they behave as Lewis base. Greater the value of \( K_b \) or smaller the value of \( pK_b \), stronger is the base. Amines are more basic than alcohols, ethers, esters, etc. The basic character of aliphatic amines should increase with the increase of alkyl substitution. But it does not occur in a regular manner as a secondary aliphatic amine is unexpectedly more basic than a tertiary amine in aqueous solutions. Aromatic amines are weaker bases than ammonia and aliphatic amines. Electron releasing groups such as \(–CH_3\), \(–NH_2\), etc., increase the basicity while electron-withdrawing substituents such as \(–NO_2\), –CN, halogens, etc., decrease the basicity of amines. The effect of these substituents is more at the p₊ than at m₋ position.
- Assertion (A): Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis. Reason (R): Aryl halides do not undergo nucleophilic substitution reaction with the anion formed by phthalimide.
- Give plausible explanation for each of the following:
Amides are less basic than amines.
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