Which of the following is not a disproportionation reaction ?

Options

A. `P_(4)+overset(ө)OHrarrH_(2)PO_(2)^(ө)+PH_(3)`
B. `Cl_(2)+overset(ө)OHrarrCl^(ө)+ClO^(ө)`
C. `2H_(2)O_(2)rarr2H_(2)O+O_(2)`
D. `2H_(2)O_(2)rarr2H_(2)O+O_(2)`

Explanation

To determine which of the following reactions is not a disproportionation reaction, we first need to understand what a disproportionation reaction is. A disproportionation reaction is a type of redox reaction in which a single substance is both oxidized and reduced, resulting in two different products containing the same element in different oxidation states.

### Step-by-Step Solution:

1. **Identify the Reactions**: We have four reactions to analyze for disproportionation:
- Reaction 1: P4 → H2PO2 + P3
- Reaction 2: Cl2 → Cl- + ClO
- Reaction 3: H2O2 → H2O + O2
- Reaction 4: H2O2 → H2O + O2 (this seems to be a repeated mention, but we will treat it as a separate reaction for analysis)

2. **Analyze Reaction 1 (P4 → H2PO2 + P3)**:
- Oxidation states: P in P4 is 0, in H2PO2 it is +1, and in P3 it is -3.
- Here, P is oxidized from 0 to +1 and reduced from 0 to -3.
- Since the same element (P) is both oxidized and reduced, this is a disproportionation reaction.

3. **Analyze Reaction 2 (Cl2 → Cl- + ClO)**:
- Oxidation states: Cl in Cl2 is 0, in Cl- it is -1, and in ClO it is +1.
- Cl is oxidized from 0 to +1 and reduced from 0 to -1.
- Again, the same element (Cl) is both oxidized and reduced, so this is also a disproportionation reaction.

4. **Analyze Reaction 3 (H2O2 → H2O + O2)**:
- Oxidation states: O in H2O2 is -1, in H2O it is -2, and in O2 it is 0.
- O is reduced from -1 to -2 and oxidized from -1 to 0.
- The same element (O) is both oxidized and reduced, making this a disproportionation reaction.

5. **Analyze Reaction 4 (H2O2 → H2O + O2)**:
- This is the same as Reaction 3, so the analysis remains the same.
- It is also a disproportionation reaction.

6. **Conclusion**: Since all the reactions analyzed involve the same element being both oxidized and reduced, they all qualify as disproportionation reactions. If the question is asking for one that is not a disproportionation reaction, it appears that all provided options are indeed disproportionation reactions.

### Final Answer:
All of the reactions listed are disproportionation reactions. Therefore, none of them is an example of a reaction that is not a disproportionation reaction.