Compound A is converted to B on reaction with CHCl3 and KOH. The compound B is toxic and can be deco

Q: Why don't secondary or tertiary amines give the Carbylamine test?

The mechanism requires the nitrogen atom to lose two protons to form the coordinate triple bond with carbon. Secondary and tertiary amines lack the necessary two hydrogen atoms on nitrogen.

Q: Why is the product B considered toxic?

Isonitriles (or carbylamines) are highly volatile and have an extremely foul, nauseating odor. They are toxic if inhaled in significant amounts.

Q: Can we use NaOH instead of KOH in the Carbylamine reaction?

Yes, NaOH can also be used. Both are strong alkalis that help in the generation of the dichlorocarbene intermediate from chloroform.

Q: Why does the isonitrile decompose in acid but not in base?

Isonitriles lack an acidic proton and are electron-rich at the carbon atom, making them stable to nucleophilic attack by bases. However, they are susceptible to electrophilic attack by protons in acidic mediums, leading to hydrolysis.

Q: What is the intermediate formed in the Carbylamine reaction?

The reaction proceeds via the formation of dichlorocarbene ($:CCl_2$), a highly reactive electrophilic intermediate generated from chloroform and the strong base.

Question

Compound A is converted to B on reaction with $	ext{CHCl}_3$ and KOH. The compound B is toxic and can be decomposed by C. A, B and C respectively are

Options:

(A) primary amine, nitrile compound, conc. HCl

(B) secondary amine, isonitrile compound, conc. NaOH

(C) primary amine, isonitrile compound, conc. HCl

(D) secondary amine, nitrile compound, conc. NaOH

Sigma Percentile · Accepted Answer

### The Mystery of the Toxic Compound

Let's decode this organic chemistry mystery. We are given a compound **A** that reacts with chloroform ($CHCl_3$) and potassium hydroxide (KOH) to form a toxic compound **B**. Then, **B** is decomposed by another reagent **C**.

Whenever you see chloroform and KOH reacting together with a nitrogenous compound, your mind should immediately jump to the **Carbylamine reaction**. This is a very specific and famous test in organic chemistry.

### The Carbylamine Revelation

The Carbylamine test is given exclusively by **primary amines** ($1^\circ$ amines). Secondary and tertiary amines simply do not react under these conditions.

Since it's the Carbylamine reaction, compound **A** has to be a primary amine ($R-NH_2$). And what about the product **B**? The reaction of a primary amine with $CHCl_3$ and KOH forms an **isonitrile** ($R-N\equiv C$), also known as a carbylamine.

Isonitriles are infamous for their extremely foul, nauseating, and toxic odor. This perfectly aligns with the problem's description of compound **B** being toxic.

### Breaking Down the Isonitrile

Now, how do we decompose this toxic isonitrile **B**? Here is a catch that often confuses students.

Isonitriles are highly stable in basic mediums because they lack an acidic proton and are electron-rich at the carbon atom, making them resistant to nucleophilic attack by bases. However, they readily hydrolyze in the presence of aqueous acids.

When treated with an acid like concentrated HCl, the isonitrile undergoes electrophilic attack by protons, leading to its hydrolysis. This reaction gives back the original primary amine ($R-NH_2$) and formic acid ($HCOOH$).

Therefore, the decomposing reagent **C** must be **concentrated HCl**.

### The Final Verdict

So, putting all the pieces of the puzzle together:
- **A** is a **primary amine**.
- **B** is an **isonitrile compound**.
- **C** is **concentrated HCl**.

This perfectly matches our third option.

Think about this: why don't secondary or tertiary amines give the Carbylamine test? It's because the mechanism requires the nitrogen atom to lose two protons to form the coordinate triple bond with carbon. Keep this crucial detail in mind for your exams!

Animated Solution for Chemistry - Organic Chemistry: Compound A is converted to B on reaction with $CHCl_{3}$ and KOH. The compound B is toxic and can be decomposed by C. A, B and C respectively are

Select Answer:

Visualized Solution

$Decoding the Reaction Sequence$

$The Carbylamine Reaction$

$Identifying A and B$

$Decomposition of Isonitrile$

$Final Conclusion$

$The Way Forward$

The Sigma Insight: Amines

The Mystery of the Toxic Compound

The Carbylamine Revelation

Breaking Down the Isonitrile

The Final Verdict

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