Isocyanide reaction involves the intermediate formation of -

Options

A. `CI_(2)`
B. `CH_(2)^(+)`
C. `CH_(3)^(-)`
D. `"CCI"_(3)`

Answer

To solve the question regarding the intermediate formation in the isocyanide reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**: The preparation of isocyanides is typically done through the carbylamine reaction, which involves the reaction of primary amines with chloroform in the presence of a base.

**Hint**: Recall that the carbylamine reaction is a method to synthesize isocyanides.

2. **Starting Materials**: The primary amine (RNH2) and chloroform (CHCl3) are the reactants involved in this reaction.

**Hint**: Identify the reactants that are essential for the carbylamine reaction.

3. **Dehydrohalogenation**: In the presence of a base, chloroform undergoes dehydrohalogenation to form dichlorocarbene (CCl2). This step involves the removal of hydrogen and chlorine atoms.

**Hint**: Understand the concept of dehydrohalogenation and how it leads to the formation of reactive intermediates.

4. **Formation of Dichlorocarbene**: The reaction proceeds by the removal of a hydrogen atom and a chlorine atom from chloroform, resulting in the formation of dichlorocarbene (CCl2).

**Hint**: Focus on the mechanism of how chloroform transforms into dichlorocarbene.

5. **Nucleophilic Attack**: The dichlorocarbene (CCl2) acts as an electrophile and reacts with the lone pair of electrons on the nitrogen atom of the primary amine (RNH2). This forms an intermediate where the nitrogen is bonded to the dichlorocarbene.

**Hint**: Remember that nucleophiles donate electrons to electrophiles in a reaction.

6. **Formation of the Isocyanide**: After the formation of the intermediate, a proton (H+) is removed, leading to the formation of isocyanide (R-N≡C). The final product is isocyanide, which is characterized by the presence of a triple bond between nitrogen and carbon.

**Hint**: Consider the final steps of proton removal and how it leads to the formation of the isocyanide structure.

### Final Answer:
The intermediate formed during the isocyanide reaction is **dichlorocarbene (CCl2)**.