In Tollen's test, aldehydes

Options

A. Are oxidised to acids
B. Are reduced to alcohol
C. Neither reduced nor oxidised
D. Precipitate `Ag^(+)` as AgCl

Answer

To answer the question regarding Tollen's test and its relation to aldehydes, we will break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Tollen's Reagent**:
- Tollen's reagent is an ammoniacal solution of silver nitrate (AgNO3). It is prepared by mixing silver nitrate with ammonium hydroxide (NH4OH).
- The reaction produces a complex ion, [Ag(NH3)2]+, which is the active component in Tollen's test.

2. **Reaction with Aldehydes**:
- Aldehydes, represented generally as RCHO, react with Tollen's reagent.
- When an aldehyde is present, it undergoes oxidation to form a carboxylic acid (RCOOH).

3. **Oxidation-Reduction Process**:
- During this reaction, the aldehyde (RCHO) is oxidized to a carboxylic acid (RCOOH).
- Simultaneously, the silver ion (Ag+) in Tollen's reagent is reduced to metallic silver (Ag).
- The overall reaction can be summarized as:
\[ RCHO + 2[Ag(NH3)2]^+ + 3OH^- \rightarrow RCOOH + 2Ag + 4NH3 + 2H2O \]

4. **Formation of Silver Mirror**:
- The reduction of silver ions to metallic silver leads to the deposition of silver on the inner surface of the test tube, creating a shiny silver mirror. This is why Tollen's test is often referred to as the "silver mirror test."

5. **Conclusion**:
- In Tollen's test, aldehydes are oxidized to carboxylic acids while the silver ions are reduced to metallic silver. This test is specific for aldehydes, as ketones do not undergo this reaction under the same conditions.