Which of the following is an example of self-oxidation reduction?

Cannizzaro reaction 

The correct answer is option 1. Cannizzaro reaction .

Out of the listed reactions, the one that exemplifies self-oxidation reduction is Cannizzaro reaction.

The Cannizzaro reaction involves a single molecule of an aldehyde (without an alpha-hydrogen atom) undergoing both oxidation and reduction simultaneously.

Oxidation: One part of the molecule is oxidized to a carboxylic acid salt (anion)

Reduction: Another part of the same molecule is reduced to a primary alcohol.

No external oxidizing or reducing agents are involved in the Cannizzaro reaction. The reaction utilizes the inherent reactivity of the aldehyde functional group to achieve both oxidation and reduction within the same molecule.

Let us explore the other reactions and why they aren't examples of self-oxidation reduction:

Darzens reaction: This reaction involves an aldehyde or ketone reacting with an α-haloester in the presence of a base to form a β-hydroxy ester. External oxidizing or reducing agents are typically used.

Reformatsky reaction: This reaction involves an α-haloester reacting with a ketone ester in the presence of zinc to form a β-hydroxy ester. Similar to the Darzens reaction, it requires external reagents.

Aldol condensation: This reaction involves condensation between two carbonyl compounds (aldehydes or ketones) to form a β-hydroxy carbonyl compound. Again, external reagents are necessary.

Therefore, the Cannizzaro reaction stands out as the only example of self-oxidation reduction among the given choices.