When `R-C-=CH` is treated with cuprous in ammonical medium, product formed is

Options

A. `R-C-=C-Cu`
B. `Cu-C-=CH`
C. `CuC-=C Cu`
D. `R-C-=C-R`

Answer

To solve the question regarding the reaction of `R-C≡CH` with cuprous ions in an ammonical medium, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**: The reactant is `R-C≡CH`, which is a terminal alkyne. The `R` represents an alkyl group, and `C≡CH` indicates a carbon-carbon triple bond where one carbon is bonded to a hydrogen atom.

2. **Understand the Reaction Conditions**: The reaction involves treating the terminal alkyne with cuprous ions (Cu⁺) in an ammonical medium (NH₄OH). This medium typically provides a basic environment.

3. **Recognize the Acidity of Terminal Alkynes**: The hydrogen atom attached to the terminal carbon (the one bonded to `C≡C`) is acidic. This means that it can be removed as a proton (H⁺) in the presence of a strong base or a reactive metal.

4. **Formation of the Alkyne Anion**: When `R-C≡CH` is treated with cuprous ions in the ammonical medium, the acidic hydrogen is removed, resulting in the formation of the alkyne anion `R-C≡C⁻`. This step involves the loss of H⁺ from the terminal alkyne.

5. **Nucleophilic Attack on Cuprous Ion**: The negatively charged carbon in the alkyne anion (`R-C≡C⁻`) can now act as a nucleophile. It attacks the cuprous ion (Cu⁺), leading to the formation of a new compound.

6. **Product Formation**: The final product of this reaction is `R-C≡C-Cu`, which is a copper acetylide. This indicates that the copper is now bonded to the terminal carbon of the alkyne.

### Final Answer:
The product formed when `R-C≡CH` is treated with cuprous ions in an ammonical medium is `R-C≡C-Cu`.