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The disproportion reaction is also called a dismutation reaction.
The disproportion reaction can be defined as both oxidation and reduction happening simultaneously in a single chemical reaction then the process is defined as a disproportion reaction.
A disproportionation reaction is a type of redox reaction.
Oxidation:
Oxidation can be defined as the addition of oxygen or removal of hydrogen or loss of electrons
Reduction:
The reduction can be defined as the addition of hydrogen or removal of oxygen or gaining of electrons.
Therefore, we can state that when both gaining and losing electrons are done at a time, then a disproportionate reaction takes place.
What is a disproportionate reaction?
In a single chemical reaction where both the oxidation and reduction have taken place at a time, then it is defined as a disproportion reaction.
The general form of disproportion reaction is
2X → X’ + X”
where X, X’, and X” are all different chemical species.
The vice–versa of disproportion reaction is called comproportionation reaction.
What is meant by comproportionation?
Comproportionation, also known as vice-versa of disproportionation, is a chemical compound that results in the formation of a molecule with an alternative oxidation number from reactant molecules having the very same element but different oxidation values. It’s the polar opposite of disproportion.
How do we identify which is oxidation and which is reduction?
Well, the answer is simple. It is all based on oxidation numbers. If the oxidation number is increased then we can say oxidation takes place. If the oxidation number is reduced, then we can say reduction takes place.
Examples of disproportionation reaction:
The breakdown of hydrogen peroxide is a similar example of a disproportionation process. The significantly less stable H2O2 dissociates to create highly stable H2O and O2.
2H2O2 → 2H2O + O2
The oxygen molecule in H2O2 has an oxidation state of -1. The oxidation state of this oxygen atom changes to -2 when it is reduced to H2O. The same oxygen carrier is also oxidised to O2, resulting in an oxidation state of 0.
Hypophosphorous acid dissociation (H3PO2)
Colourless phosphine gas (PH3) and phosphorous acid are formed when H3PO2 is decomposed (H3PO3).
3H3PO2 → PH3 + 2H3PO3
In H3PO2, the phosphorus atom is in the +1 oxidation state. This phosphorus is oxidised to H3PO3, resulting in a change in oxidation state from +1 to +3. The same phosphorus atom, on the other hand, is reduced to PH3. Its oxidation number reduces to -3 from 1 at this point.
2. Hypochlorous acid decomposition (HOCl)
Hydrochloric acid (HCl) and chloric acid are formed when HOCl is broken down (HClO3).
3HOCl → 2HCl + HClO3
The Cl atom in HOCl has an oxidation state of +1, which is oxidised to HClO3, which has an oxidation state of +5. The same Cl atom is reduced to HCl as well, resulting in an oxidation state -1.
3. Chlorine disproportionation reaction (Cl2)
- Chlorine interacts with sodium hydroxide (NaOH) in a cold, dilute solution to form sodium chloride (NaCl), sodium chlorite (NaClO), and water (H2O).
The oxidation state of the chlorine atom in the reactant is 0. In NaClO, it is oxidised to +1, whereas in NaCl, it is reduced to -1.
- Chlorine gas is oxidised to sodium chlorate (NaClO3) ins of NaClO when it passes through a hot and intense sodium hydroxide (NaOH) solution.
3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O
In NaClO3 and NaCl, the cl atom with oxidation number 0 achieves +5 and -1, respectively.
4. Mercurous chloride photolysis (Hg2Cl2)
Under UV light, Hg2Cl2 disproportionates to give mercury (Hg) and mercuric chloride (HgCl2).
Hg2Cl2 → Hg + HgCl2
Mercury in Hg2Cl2 has an oxidation state of +1. It oxidises to HgCl2, giving it an oxidation state of +2. It’s also changed from +1 to 0 when it’s lowered to Hg.
5. Nitrogen dioxide (NO2) reacts with water.
Nitric (HNO3) and nitrous (HNO2) acids are formed when NO2 interacts with water.
2NO2 + H2O → HNO3 + HNO2
NO2 has a +4 oxidation number for nitrogen. It is oxidised to HNO3, which has a nitrogen oxidation state of +5. It’s also reduced to HNO2, giving it an oxidation state of +3.
Conclusion:
A disproportionation reaction is one of the types of redox reactions and the gaining and losing of electrons is done at a time in a single chemical reaction. Both oxidation and reduction occur at a time. The disproportionation reaction is also called the dismutation reaction. The disproportionation reaction is mainly based on oxidation states. If the oxidation state is increased then we can say oxidation happens. If the oxidation state or oxidation number is reduced then we can say that reduction happens. Comproportination reaction is the vice versa of a disproportionation reaction.
