Structure Of Amines

Concept: Aliphatic amines > aromatic amines in basicity.

Step 1: Reason.
Aromatic amines less basic due to resonance.

Concept: Hinsberg reagent distinguishes amines:
• 1° amine reacts
• 2° amine reacts
• 3° amine does not react

Step 1: Identify amine types.

• N,N-Dimethylethanamine tertiary amine

Step 2: Conclusion.
Tertiary amines do not react with Hinsberg reagent.

Step 1: Understanding the Concept:
This is a sequence of reactions: diazotization followed by a Sandmeyer reaction.

Step 2: Detailed Explanation:
1. Aniline (C H NH ) reacts with NaNO and HCl at 273-278 K (0-5 C) to form benzene diazonium chloride, which is compound (Y). The reaction is diazotization. 2. When benzene diazonium chloride is treated with Cu/HBr (a Sandmeyer reaction), the diazonium group (-N ) is replaced by a bromine atom (-Br), forming bromobenzene (C H Br), which is compound 'Z'.

Step 3: Final Answer:
Compound 'Z' is bromobenzene.

Step 1: Understanding the Concept:
The carbylamine reaction (also known as the isocyanide test) is a characteristic test for primary amines.

Step 2: Detailed Explanation:
When a primary amine (like aniline) is heated with chloroform (CHCl ) and a strong base (like alcoholic KOH), it forms an isocyanide (carbylamine), which has a very foul smell. The reaction is: Aniline (C H NH ) gives phenyl isocyanide (C H NC).

Step 3: Final Answer:
Carbylamine is obtained when aniline is heated with CHCl and ethanolic KOH.

Concept:
• Boiling point depends on hydrogen bonding

Step 1: Order of H-bonding
Primary > Secondary > Tertiary

Step 2: Arrange
Tertiary < Secondary < Primary Final Conclusion:
Option (A)

Concept:
• Carbylamine test → only primary amines

Step 1: Identify type
N-Methylethanamine → secondary amine

Step 2: Conclusion
Secondary amines do not give carbylamine test Final Conclusion:
Option (E)

Step 1: Understanding the Concept:
The value is a quantitative measure of the basic strength of a compound. A lower value indicates a stronger base (since ). The basicity of aliphatic amines in an aqueous solution depends on a delicate balance of inductive effect, solvation (hydration) effect, and steric hindrance.

Step 2: Key Formula or Approach:
Identify the class of each amine ( ) and apply the established trend for their basicity in an aqueous medium. For ethyl-substituted amines, the order of basicity is .

Step 3: Detailed Explanation:
Let's classify the given options:
- (A) Methanamine: Primary ( ) methylamine
- (B) Ethanamine: Primary ( ) ethylamine
- (C) N-ethylethanamine: Secondary ( ) ethylamine (Diethylamine)
- (D) N,N-diethylethanamine: Tertiary ( ) ethylamine (Triethylamine)
In an aqueous environment, secondary amines are generally the strongest bases. They possess a good balance: two alkyl groups provide a strong electron-donating inductive (+I) effect to increase electron density on the nitrogen, while still retaining a hydrogen atom to allow for effective stabilization of the conjugate acid via hydrogen bonding with water.
Tertiary amines have a stronger +I effect but suffer from significant steric hindrance, which prevents effective hydration of their conjugate acid, making them weaker bases than secondary amines in water. Primary amines have less steric hindrance but a weaker +I effect.
Therefore, N-ethylethanamine (a amine) is the strongest base among the choices and will have the highest and the least value.

Step 4: Final Answer:
N-ethylethanamine has the least value.