Which does not undergo comproportionation reaction?

Options

A. `H_(2)S+SO_(2) to `
B. `I^(-)(aq.)+IO_(3)^(-)(aq.)+H^(+)(aq.)to`
C. `K_(2)MnO_(4)+H^(+)(aq.)to`
D. `MnO_(4)^(-)+Mn^(2+)(aq.)to`

Explanation

To determine which reaction does not undergo comproportionation, we first need to understand what a comproportionation reaction is. In a comproportionation reaction, two different oxidation states of the same element react to form a single oxidation state.

### Step-by-Step Solution:

1. **Identify the Reactions**: We have four options to analyze:
- A: H2S + SO2
- B: I- + IO3- + H+
- C: K2MnO4 + H+
- D: MnO4- + Mn2+

2. **Analyze Option A (H2S + SO2)**:
- In H2S, sulfur has an oxidation state of -2.
- In SO2, sulfur has an oxidation state of +4.
- These two oxidation states can combine to form elemental sulfur (S) with an oxidation state of 0.
- Therefore, this option undergoes comproportionation.

3. **Analyze Option B (I- + IO3- + H+)**:
- In I-, iodine has an oxidation state of -1.
- In IO3-, iodine has an oxidation state of +5.
- These two oxidation states can combine to form elemental iodine (I2) with an oxidation state of 0.
- Therefore, this option also undergoes comproportionation.

4. **Analyze Option C (K2MnO4 + H+)**:
- In K2MnO4, manganese has an oxidation state of +6.
- This will disproportionate to +7 (in KMnO4) and +4 (in MnO2).
- Since it forms two different oxidation states, this is not a comproportionation reaction.

5. **Analyze Option D (MnO4- + Mn2+)**:
- In MnO4-, manganese has an oxidation state of +7.
- In Mn2+, manganese has an oxidation state of +2.
- These two oxidation states can combine to form MnO2 with an oxidation state of +4.
- Therefore, this option undergoes comproportionation.

### Conclusion:
The reaction that does not undergo comproportionation is **C: K2MnO4 + H+**.