Chemistry 2002 JAMB Past Questions - Question 35: A red precipitate of copper (I) carbide is formed when ammonium solution of copper (I) chloride is introduced into

Correct Answer

C

Explanation

The chemical reactions you provided seem to involve the reaction of an ammonium solution of copper(I) chloride with different organic compounds, resulting in the formation of a red precipitate of copper(I) carbide. However, it appears that the chemical structures are not fully specified in your text. I'll try to provide a general explanation based on the information you've given.

The formation of a red precipitate of copper(I) carbide suggests the reduction of copper(II) to copper(I) and subsequent reaction with carbon-containing compounds.

Let's consider the possible reactions with the organic compounds you mentioned:

1. **Câ‚‚Hâ‚…NHâ‚‚ (Ethylamine):**
  \[ \text{2 CuCl} + \text{2 Câ‚‚Hâ‚…NHâ‚‚} \rightarrow \text{2 Cu} + \text{2 NHâ‚„Cl} + \text{Câ‚‚H₆} \]

  Here, copper(II) chloride is reduced to copper(I), and ethylamine is oxidized to form ethane.

2. **CHâ‚‚=CH-CH=CH-CHâ‚‚ (1,3-butadiene):**
  \[ \text{2 CuCl} + \text{2 CHâ‚‚=CH-CH=CH-CHâ‚‚} \rightarrow \text{2 Cu} + \text{2 ClCH=CH-CH=CH-CHâ‚‚} \]

  The copper(II) chloride is reduced to copper(I), and 1,3-butadiene undergoes a reaction, possibly forming a chlorinated product.

3. **CH₃CH₂-C=CH (1-butene):**
  \[ \text{2 CuCl} + \text{2 CH₃CHâ‚‚-C=CH} \rightarrow \text{2 Cu} + \text{2 ClCH₃CHâ‚‚-C=CH} \]

  Similar to the previous case, copper(II) chloride is reduced to copper(I), and 1-butene undergoes a reaction, possibly forming a chlorinated product.

4. **CH₃-C = C-CH₃ (2-butene):**
  \[ \text{2 CuCl} + \text{2 CH₃-C = C-CH₃} \rightarrow \text{2 Cu} + \text{2 ClCH₃-C = C-CH₃} \]

  Again, copper(II) chloride is reduced to copper(I), and 2-butene undergoes a reaction, possibly forming a chlorinated product.

In all cases, the reduction of copper(II) to copper(I) is a key step, and the organic compounds are involved in the overall reaction, likely undergoing some form of chlorination or other reactions. The specific products and mechanisms would depend on the reaction conditions and the nature of the organic compounds.