Which of the following substances undergo(s) disproportionation reactions under basic medium?

Options

A. `F_(2)`
B. `P_(4)`
C. `S_(8)`
D. `Br_(2)`

Explanation

To determine which substances undergo disproportionation reactions under basic medium, we need to analyze each substance and see if they can exist in three different oxidation states and if they can simultaneously undergo oxidation and reduction.

### Step-by-Step Solution:

1. **Understanding Disproportionation Reactions**:
- A disproportionation reaction is a type of redox reaction where an element in one oxidation state is simultaneously oxidized and reduced to form two different products. For this to occur, the element must exist in at least three different oxidation states.

2. **Analyzing Fluorine (F)**:
- Fluorine is the most electronegative element and typically exists in the -1 oxidation state. It does not exhibit positive oxidation states and therefore cannot undergo disproportionation.
- **Conclusion**: Fluorine does not undergo disproportionation.

3. **Analyzing Phosphorus (P4)**:
- In the case of P4, phosphorus can exist in multiple oxidation states. In basic medium, P4 can disproportionate to form phosphite ions (H2PO2-) and phosphine (PH3).
- The oxidation states change as follows:
- P in P4 (0) → P in PH3 (-3) (reduction)
- P in P4 (0) → P in H2PO2+ (1) (oxidation)
- **Conclusion**: Phosphorus undergoes disproportionation.

4. **Analyzing Sulfur (S8)**:
- Sulfur can also exist in multiple oxidation states. In basic medium, S8 can disproportionate to form sulfide ions (S2-) and sulfate ions (SO4^2-).
- The oxidation states change as follows:
- S in S8 (0) → S in S2- (-2) (reduction)
- S in S8 (0) → S in SO4^2+ (6) (oxidation)
- **Conclusion**: Sulfur undergoes disproportionation.

5. **Analyzing Bromine (Br2)**:
- Bromine can exist in multiple oxidation states as well. In basic medium, Br2 can disproportionate to form bromate ions (BrO-) and bromide ions (Br-).
- The oxidation states change as follows:
- Br in Br2 (0) → Br in BrO- (+1) (oxidation)
- Br in Br2 (0) → Br in Br- (-1) (reduction)
- **Conclusion**: Bromine undergoes disproportionation.

### Final Conclusion:
The substances that undergo disproportionation reactions under basic medium are:
- Phosphorus (P4)
- Sulfur (S8)
- Bromine (Br2)