Question

Which of the following are {insoluble in alkali} when reacted with Hinsberg reagent?

• A. 8
• B. 5
• C. 6
• D. 7

Hint:

In Hinsberg test: Primary amine $\rightarrow$ soluble in alkali, Secondary amine $\rightarrow$ {insoluble in alkali}, Tertiary amine $\rightarrow$ no reaction.

Answer 1

The Correct Option is B

Concept (Hinsberg Test):
Hinsberg reagent (benzene sulphonyl chloride) distinguishes amines based on their behavior in alkali:

Primary amines
form sulphonamides soluble in alkali (due to acidic N–H).
Secondary amines
form sulphonamides insoluble in alkali
(no acidic hydrogen).
Tertiary amines
do not react and remain insoluble but dissolve in dilute acids.

Step 1: Identify Secondary Amines
From the given structures:

Secondary amines have the general form \(R{-}NH{-}R'\).
They react with Hinsberg reagent but their products are insoluble in alkali
.

Step 2: Count Secondary Amines
On analyzing the given structures:

Number of secondary amines
present = \(\boxed{5}\)
These are insoluble in alkali after Hinsberg reaction.
Primary amines are soluble in alkali, tertiary amines do not form sulphonamides.
Final Conclusion:
Number of compounds insoluble in alkali after Hinsberg test: \[ \boxed{5} \]