Why is the oxidation of a primary alcohol with mixture of sodium dichromate and sulphuric acid not a good method for the preparation of corresponding aldehyde ?

Options

A. The product will be the corresponding ketone
B. Any aldehyde produced will be oxidised further
C. The product will be an alkyl sulphonate , `R-SO_3H` mixture of sodium dichromate and sulphuric acid will not oxidize a primary alcohol
D. A mixture of sodium dichromate and sulphuric acid will not oxidized a primary alcohol

Answer

To understand why the oxidation of a primary alcohol with a mixture of sodium dichromate and sulfuric acid is not a good method for preparing the corresponding aldehyde, we can break down the process step by step:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- We start with a primary alcohol, which can be represented as RCH2OH, where R is an alkyl group.
- The oxidizing agents used are sodium dichromate (Na2Cr2O7) and sulfuric acid (H2SO4).

2. **Oxidation Reaction**:
- When a primary alcohol is treated with sodium dichromate in the presence of sulfuric acid, the primary alcohol is oxidized to an aldehyde (RCHO).
- The reaction can be represented as:
\[ RCH2OH \xrightarrow{Na2Cr2O7, H2SO4} RCHO \]

3. **Further Oxidation of Aldehyde**:
- Aldehydes are more reactive than primary alcohols and can be further oxidized. If the conditions are not controlled, the aldehyde (RCHO) can be oxidized to a carboxylic acid (RCOOH).
- The reaction for this step is:
\[ RCHO \xrightarrow{Na2Cr2O7, H2SO4} RCOOH \]

4. **Conclusion on Method Suitability**:
- Since sodium dichromate and sulfuric acid are strong oxidizing agents, they do not selectively stop at the aldehyde stage. Instead, they tend to oxidize the aldehyde further to a carboxylic acid.
- Therefore, if the goal is to prepare an aldehyde from a primary alcohol, this method is not suitable because it leads to the formation of carboxylic acids instead of the desired aldehyde.

### Final Answer:
The oxidation of a primary alcohol with a mixture of sodium dichromate and sulfuric acid is not a good method for preparing the corresponding aldehyde because the strong oxidizing agents can further oxidize the formed aldehyde into a carboxylic acid.