Question

Aldehydes are good reducing agents. explain by giving their reactions.

Answer 1

Aldehydes are easily oxidized to carboxylic acids on treatment with common oxidizing agents like HNO₃, KMNO₄, K₂Cr₂O₇ etc even mild oxidizing agents also. Mainly Tollen’s reagent and Fehling’s reagent also oxidise aldehyde.

Thus aldehydes act as strong reducing agents.
For example:

(i) Aldehyde reduces Tollen’s reagent into metallic silver.

(ii) Aldehydes reduce Fehling’s solution.

(iii) Aldehydes reduce Benedict’s solution.

Answer 2

A simple reaction to prove this will be heating any other carboxylic acid with formic acid in presence of Manganese Dioxide. As is evident, HCOOH is oxidised to Carbon Dioxide. Hence it will itself behave as a reducing agent. ... It always oxidises (in presence of suitable reagents) to give Carbon Dioxide.