The species which undergo disproportionation in alkaline medium is/ are

Options

A. `Cl_2`
B. `MnO_4^(-)`
C. `NO_2`
D. Both A and C

Answer

To determine which species undergo disproportionation in alkaline medium, we need to analyze each option provided in the question. Disproportionation is a specific type of redox reaction where a species is simultaneously oxidized and reduced, resulting in two different products.

### Step-by-Step Solution:

1. **Understanding Disproportionation**:
- Disproportionation occurs when a single species is both oxidized and reduced in a reaction.
- For a species to undergo disproportionation, it must have at least two different oxidation states.

2. **Analyzing Cl2**:
- The oxidation state of chlorine (Cl) in Cl2 is 0.
- Chlorine can be reduced to -1 (Cl-) or oxidized to +1, +3, +5, or +7.
- Since Cl2 can both gain electrons (to become Cl-) and lose electrons (to become Cl+), it can undergo disproportionation.
- **Conclusion**: Cl2 undergoes disproportionation.

3. **Analyzing MnO4-**:
- The oxidation state of manganese (Mn) in MnO4- is +7.
- The maximum oxidation state of Mn is +7, meaning it cannot be oxidized further.
- MnO4- can only be reduced (to Mn2+, Mn3+, etc.) but cannot undergo oxidation.
- **Conclusion**: MnO4- does not undergo disproportionation.

4. **Analyzing NO2**:
- The oxidation state of nitrogen (N) in NO2 is +4.
- Nitrogen can be reduced to +3, +2, +1, or even 0, and can also be oxidized to +5.
- Since NO2 can both gain electrons (to become NO or N2O) and lose electrons (to become N2O5), it can undergo disproportionation.
- **Conclusion**: NO2 undergoes disproportionation.

5. **Final Conclusion**:
- The species that undergo disproportionation in alkaline medium are Cl2 and NO2.
- Therefore, the correct option is both A (Cl2) and C (NO2).

### Final Answer:
The species which undergo disproportionation in alkaline medium is/are Cl2 and NO2 (Option 4: Both A and C).