Which of the following does not disproportionate?

Options

A. `Cu^(+)`
B. `Au^(3+)`
C. `Cu^(2+)`
D. `Au^(+)`

Answer

To determine which of the following does not undergo disproportionation, we first need to understand what a disproportionation reaction is.

### Step-by-Step Solution:

1. **Define Disproportionation Reaction**:
A disproportionation reaction is a type of redox reaction where a single substance is both oxidized and reduced simultaneously. This means that one part of the substance loses electrons (is oxidized) while another part gains electrons (is reduced).

2. **Identify Examples of Disproportionation**:
A common example is the reaction of chlorine gas (Cl₂) with sodium hydroxide (NaOH):
- Cl₂ (oxidation state 0) reacts with NaOH to produce:
- NaCl (where Cl is in the -1 oxidation state, reduced)
- NaClO (where Cl is in the +1 oxidation state, oxidized)
In this case, Cl₂ is both oxidized and reduced, confirming it is a disproportionation reaction.

3. **Analyze the Given Options**:
The question asks which of the following does not undergo disproportionation. We need to evaluate the oxidation states of the species provided in the options:
- **Cu⁺ (Copper(I))**: This is a unipositive ion. It can either be oxidized to Cu²⁺ or reduced to Cu, but it cannot do both simultaneously. Therefore, Cu⁺ does not undergo disproportionation.
- **Au⁺ (Gold(I))**: Similar to Cu⁺, Au⁺ is also a unipositive ion. It can either be oxidized to Au³⁺ or reduced to Au, but again, it cannot do both at the same time. Thus, Au⁺ does not undergo disproportionation.

4. **Conclusion**:
Since both Cu⁺ and Au⁺ are unipositive ions that cannot simultaneously undergo oxidation and reduction, they do not participate in disproportionation reactions.

### Final Answer:
The species that does not undergo disproportionation are **Cu⁺ and Au⁺**.