Oxidation Reaction

A chemical reaction called oxidation occurs when an atom, molecule, or ion loses electrons or experiences an increase in oxidation status. This procedure can be carried out either by removing hydrogen atoms from a molecule or by reacting with an oxidising substance like oxygen or hydrogen peroxide.

New compounds can be created during oxidation processes, or existing compounds can undergo modification. For instance, secondary alcohols can be oxidised to form carboxylic acids whereas primary alcohols can be oxidised to form aldehydes or ketones. The generation of energy and metabolism depend heavily on oxidation processes in biological systems.

Since it enables the creation of new compounds and the change of old compounds into various forms, oxidation is a crucial chemical process. It is also a significant industrial process since it is used to create a wide range of goods, such as chemicals, fuels, and medicines.

Oxidation of Aldehyde

Aldehydes can be oxidised to produce either pure carboxylic acids or a combination of alcohols and carboxylic acids. Aldehydes are often oxidised using the reagents potassium permanganate (KMnO₄), chromic acid (H₂CrO₄), and silver nitrate (AgNO₃). These substances will react with the aldehyde group and produce carboxylic acid under the proper circumstances. Propanoic acid, for instance, is produced when potassium permanganate and propanal are combined.

Mechanism for Oxidation of Aaldehyde Using K₂Cr₂O₇

In the presence of an acidic solution, the aldehyde is protonated to form a more electrophilic carbonyl group.

RCHO + H⁺ → RCH(OH)₂⁺

Chromate Ester is formed by the attack of the carbonyl oxygen on the chromium in the K₂Cr₂O₇

RCH(OH)₂+ + Cr₂O₇^2- → RCH(OH)(OCrO)^2-

Chromate Ester rearranges to form a more stable intermediate.

RCH(OH)(OCrO)^2- → RCO(OH)(OCrO)^2-

Water is eliminated from the intermediate to form a carboxylic acid.

RCO(OH)(OCrO)^2- → RCO(O)CrO₃ + H₂O

Chromium in the product is reduced from the +6 oxidation state to the +3 oxidation state, forming Cr(OH)₃

2CrO₃ + 3H₂O → Cr(OH)₃ + 3H₂CrO₄

Overall Reaction

RCHO + [O] → RCOOH

Oxidation of Ketone 

As ketones are oxidised, carboxylic acids can be produced on their own or in combination with other compounds. Nitric acid and potassium permanganate (KMnO₄) are the two typically utilised chemicals for oxidising ketones (HNO₃). These substances will react with the ketone group to produce carboxylic acid under the proper circumstances. Acetic acid, for instance, is produced when potassium permanganate and acetone are combined.

Mechanism for the oxidation of a Ketone using KMnO₄

In the presence of an acidic solution, the ketone is protonated to form a more electrophilic carbonyl group.

R₂C=O + H⁺ → R₂C=OH₂⁺

Carbonyl Oxygen of the protonated ketone attacks a hydrogen atom on the adjacent carbon to form a gem-diol intermediate.

R₂C=OH₂⁺ + H-CR₂ → R₂C(OH)(CR₂)(OH₂⁺)

The potassium permanganate oxidizes the gem-diol intermediate to form a diketone intermediate.

R₂C(OH)(CR₂)(OH₂⁺) + 2KMnO₄ → R₂C=O-CR₂=O + 2MnO₂ + 2KOH + 2H₂O

Water is eliminated from the diketone intermediate to form the final product.

R₂C=O-CR₂=O → R₂C=O + CR₂=O

Overall Reaction

R₂C=O + [O] → R₂C=O

Oxidation of Carboxylic Acid

Carbon dioxide and water can be produced when carboxylic acids are oxidised, as well as a combination of carbon dioxide and other organic molecules. Potassium permanganate is a reagent frequently utilised for the oxidation of carboxylic acids (KMnO₄). This reagent will react with the carboxylic acid group under the correct circumstances to produce carbon dioxide. As an illustration, the oxidation of ethanol with potassium permanganate results in the production of carbon dioxide and water.

Mechanism for the oxidation of carboxylic acid using acidic Potassium Permanganate (KMnO₄)

In the presence of an acidic solution, the carboxylic acid is protonated to form a more electrophilic carbonyl group.

RCOOH + H⁺ → RCOOH₂⁺

The carbonyl oxygen of the protonated carboxylic acid attacks a manganese atom in the KMnO4, forming a tetrahedral intermediate.

RCOOH₂⁺ + MnO₄^– → RCOOMnO₃(OH) + H₂O

The tetrahedral intermediate rearranges to form a more stable intermediate.

RCOOMnO₃(OH) → RCOO-MnO₂(OH)₂^–

Water is eliminated from the intermediate to form a carboxylate ion and manganese dioxide.

RCOO-MnO₂(OH)₂^– → RCOO^– + MnO₂ + H₂O

The manganese dioxide is reduced to form manganese ions in a basic solution.

MnO₂ + 4OH^– → MnO₄^2- + 2H₂O + 2e^–

Overall Reaction

RCOOH + [O] → CO₂ + H₂O

A carbonyl group (-C=O) is found at the end of a carbon chain, which distinguishes aldehydes from other organic molecules. They are often present in nature and have significant uses across several sectors. In this assignment, the structure, characteristics, and reactivity of aldehydes will be covered.