Disproportionation Reaction

Disproportionation Reaction is a type of reaction in which both oxidation and reduction happen in the same reaction. these reactions are also called dismutation reactions and are a type of redox reaction. The breakdown of hydrogen peroxide (2H_2​O₂​ → 2H₂​O+O₂​), is an example of a Disproportion reaction, in which oxygen experiences both oxidation and reduction.

In this article, we will learn about, Disproportion Reaction, Examples of Disproportion Reactions, and others in detail.

What are Disproportionation Reactions?

Disproportionation reactions involve both oxidation and reduction steps, hence they are categorized as redox (reduction-oxidation) reactions. These reactions result in the formation of two new compounds with distinct oxidation states because the starting material serves as both a reducing and an oxidizing agent.

Different chemical systems, such as organic, inorganic, and organometallic chemistry, can experience disproportionation reactions. They are especially prevalent in transition metal complexes, where the reaction may cause the metal center to change its oxidation state.

Disproportionation Reaction Definition

Disproportionation reaction is a type of redox reaction when a single chemical species undergoes both oxidation and reduction, two different oxidation states or products are created in a disproportionation reaction.

Learn,

• Chemical Reactions
• Types of Chemical Reactions

How to Identify a Disproportionation Reaction?

We must examine the alterations in the oxidation states of the starting material and the products to ascertain whether a chemical transformation is a disproportionation reaction. One product is more oxidized than the starting material in a disproportionation reaction, while the other product is more reduced. This indicates that during the reaction, the starting material serves as both an oxidizing and a reducing agent.

For Example:

Fe(III) + Fe(0) → 2 Fe(II)

Iron(II) (Fe(II)) is transformed into elemental iron (Fe(0)) and iron(III) (Fe(III)) in this reaction. While elemental iron is more reduced than Fe(II), iron(III) is more oxidized than the initial material. This suggests that Fe(II) functions as a reducing agent by reducing Fe(II) to Fe(0) and an oxidizing agent by oxidizing Fe(II) to Fe(III)).

How does Disproportionation Occur?

Disproportionation occurs when one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states.

Examples of Disproportionation Reactions

Some examples of disproportionation reaction are,

Desymmetrization Reactions

Desymmetrization reactions entail the breaking of a chiral molecule’s symmetry to produce an optically active compound. Disproportionation happens in these reactions because one of the products is more reduced and one is more oxidized than the starting material.

For example:

2-Butanol → Propan-2-ol + Acetone

This reaction begins with 2-butanol (CH₃CH₂CH₂CH₂OH) and yields acetone (CH₃COCH₃) and propan-2-ol (CH₃CH₂CH₃OH). Whereas 2-butanol is more oxidized than acetone, propan-2-ol is more reduced. This suggests that 2-butanol has dual effects on the oxidation and reduction of substances. It oxidizes to acetone and reduces to propan-2-ol.

Radical Disproportionation

In a reaction known as a radical disproportionation, a radical loses electrons and transforms into two distinct products. Disproportionation happens in these reactions because one of the products is more reduced and one is more oxidized than the radical that started the reaction. For example:

CH₃CHO + CH₃CH₂CHOH → CH₃CH₂CH₂CH₃

This reaction yields acetone (CH₃COCH₃) and propan-1-ol (CH₃CHOH) from a tertiary butyl radical (CH₃CH₂CH₂CH₃). Propan-1-ol is more reduced than acetone, while CH₃CH₂CH₂CH₃ is more oxidized. This suggests that CH₃CH₂CH₂CH₃ functions as a reducing agent (reducing itself to propan-1-ol) as well as an oxidizing agent (oxidizing itself to acetone).

Other Examples of Disproportionation Reactions

various other examples of disproportionation reaction are,

Chlorine Dioxide (ClO₂)

In this reaction, chlorine dioxide (ClO₂​) is both oxidized and reduced to form chlorate (ClO₃⁻_​) and chloride (Cl⁻) ions.

2ClO_{2 ​}→ ClO₃⁻​+ Cl⁻

Nitrogen Dioxide (NO₂)

Nitrogen dioxide (NO_2​) undergoes disproportionation to produce nitrate (NO₃⁻​) and nitric oxide (NO).

2NO₂ ​→ NO₃⁻​+ NO

Reverse Reaction

It is not common to witness the opposite reaction when hydrogen (H₂) undergoes disproportionation. The disproportionation process for hydrogen peroxide (H₂O₂) is as follows:

2H₂O_{2 ​} → 2H₂O + O₂

​Hydrogen peroxide breaks down into oxygen and water in this process. The opposite of this disproportionation would occur when oxygen and water combine to form hydrogen peroxide, however this reaction is rarely seen in everyday situations. Thermodynamically, the forward response is more advantageous.

Related Resources,

• Oxidation Number
• Effects of Oxidation Reactions
• Balancing Redox Reactions

Frequently Asked Questions on Disproportionation Reaction

Define Disproportionation Reaction.

Disproportionation Reaction is a chemical reaction in which same substance underges both oxidation and reduction forming two different states of itself

What is Auto-oxidation and Auto-Reduction?

• Oxidation that happens naturally without the assistance of external agents is referred to as autooxidation.
• Auto-Reduction: Refers to reduction that takes place organically without the assistance of external agents.

What are Industrial Applications of Disproprotionation reaction?

Industrial applications for Disproportionation reactions include the synthesis of perchlorates and the manufacturing of materials.

Which Reaction is Opposite of Disproportionation Reaction?

Reaction which is opposite to Disproportionation reaction is Comproportionation reaction. Example, Ag²⁺ (aq) + Ag (s) → 2Ag⁺ (aq)

What is an Example of Disproportionation?

An example of disproportionation reaction is decomposition of hydrogen peroxide.