Which of the following species do not show disproportionation reaction?

Question

Accepted Answer

To determine which species do not show disproportionation reactions, we need to understand the concept of disproportionation. Disproportionation is a type of redox reaction in which a single substance is simultaneously oxidized and reduced, forming two different products.

Let's analyze each option:

1. **$ClO^{-}$ (Hypochlorite ion):**  
   The hypochlorite ion can undergo disproportionation. In a typical disproportionation reaction, $ClO^{-}$ can be converted into $Cl^{-}$ and $ClO_{3}^{-}$, where chlorine is both reduced to $Cl^{-}$ and oxidized to $ClO_{3}^{-}$.

2. **$ClO_{2}^{-}$ (Chlorite ion):**  
   The chlorite ion is also capable of undergoing disproportionation. It can disproportionate to form $ClO_{3}^{-}$ and $Cl^{-}$, where chlorine is again both reduced and oxidized.

3. **$ClO_{3}^{-}$ (Chlorate ion):**  
   The chlorate ion can undergo disproportionation as well. It can disproportionate to form $ClO_{4}^{-}$ and $Cl^{-}$, where chlorine is both reduced and oxidized.

4. **$ClO_{4}^{-}$ (Perchlorate ion):**  
   The perchlorate ion is the most oxidized form of chlorine in these oxyanions and does not undergo disproportionation. This is because there is no higher oxidation state for chlorine than +7 in $ClO_{4}^{-}$, so it cannot be further oxidized. Additionally, it is a very stable ion and does not readily reduce to a lower oxidation state under normal conditions.

Therefore, the correct answer is Option 4: $ClO_{4}^{-}$, as it does not show disproportionation due to its stability and the fact that it is already in the highest oxidation state possible for chlorine.