The reaction of chloroform with alcoholic KOH and p-toluidine form
(a) p-tolunitrile
(b) p-tolyldiaz

Q: Do secondary or tertiary amines give this reaction?

No, the Carbylamine test is strictly for primary amines (both aliphatic and aromatic). Secondary and tertiary amines do not react to form isocyanides.

Q: What is the reactive intermediate formed in this reaction?

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

Q: Why do we use alcoholic KOH instead of aqueous KOH?

Alcoholic KOH acts as a strong base favoring elimination to generate the carbene intermediate. Aqueous KOH would act as a nucleophile and favor substitution, leading to different products.

Q: How do we practically know in a lab that this reaction has occurred?

The formation of the isocyanide product is accompanied by an extremely pungent and intolerable foul smell, which serves as the positive indicator for the test.

Q: Does the position of the methyl group in $p$-toluidine affect the reaction?

No, the methyl group at the para position is a spectator in this reaction. The Carbylamine reaction exclusively targets the primary amine ($-NH_2$) group.

Question

The reaction of chloroform with alcoholic KOH and $p$-toluidine form

Sigma Percentile · Accepted Answer

### Analyzing the Setup

Imagine you are in a chemistry lab, and you are handed a flask containing **$p$-toluidine**. This molecule is a classic primary aromatic amine, featuring an amino group ($-NH_2$) attached directly to a benzene ring, with a methyl group ($-CH_3$) sitting directly opposite to it at the *para* position.

Now, the problem asks us to react this $p$-toluidine with a very specific cocktail of reagents: **chloroform ($CHCl_3$)** and **alcoholic potassium hydroxide (KOH)**. Whenever you see this exact combination of reagents reacting with a primary amine, an alarm bell should instantly ring in your head!

### The Master Reaction: Carbylamine Test

This specific setup is the hallmark of the famous **Carbylamine Reaction**, also known as the **Isocyanide Test**. It is one of the most reliable qualitative tests used to detect the presence of primary amines.

Here is the beautiful chemistry behind it: when a primary amine (whether aliphatic or aromatic) is heated with chloroform and alcoholic KOH, it undergoes a transformation to form an **isocyanide** (or carbylamine).

$$ R-NH_2 + CHCl_3 + 3KOH \xrightarrow{\Delta} R-NC + 3KCl + 3H_2O $$

The most fascinating (and notorious) part of this reaction is the physical observation. The resulting isocyanide produces an incredibly pungent, foul, and intolerable smell. If you ever perform this in a lab, you will know immediately if your reaction was successful! It is crucial to remember that secondary and tertiary amines **do not** give this reaction, making it a perfect distinguishing test.

### Final Calculation and Product

Let's apply this master equation to our specific molecule, $p$-toluidine.

The reaction specifically targets the primary amine group. The $-NH_2$ group will be converted into an isocyanide group ($-NC$). The rest of the molecule, including the benzene ring and the *para*-methyl group, remains completely untouched.

$$ p	ext{-CH}_3-	ext{C}_6	ext{H}_4-	ext{NH}_2 + 	ext{CHCl}_3 + 3	ext{KOH (alc.)} \xrightarrow{\Delta} p	ext{-CH}_3-	ext{C}_6	ext{H}_4-	ext{NC} + 3	ext{KCl} + 3	ext{H}_2	ext{O} $$

The final product is **$p$-tolyl isocyanide**. Looking at our options, the structure that perfectly matches this transformation is option (c), where the $-NH_2$ has been replaced by $-NC$.

Animated Solution for Chemistry - Organic Chemistry: The reaction of chloroform with alcoholic KOH and $p$ -toluidine form

Select Answer:

Visualized Solution

$R e a c t an t s A na l y s i s$

$R e a g e n t I d e n t i f i c a t i o n$

$C a r b y l amin e R e a c t i o n$

$P r o d u c t F or ma t i o n$

The Sigma Insight: Amines

Analyzing the Setup

The Master Reaction

Final Calculation and Product

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Animated Solution for Chemistry - Organic Chemistry: .math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The reaction of chloroform with alcoholic KOH and p-toluidine form