Question

Which product will be formed during Etard’s reaction?

• A. Benzoic acid
• B. Benzyl alcohol
• C. Benzaldehyde
• D. Benzene

Hint:

Etard's reaction is highly selective. Chromyl chloride ($CrO_2Cl_2$) acts as a controlled oxidizing agent that arrests the oxidation at the aldehyde stage ($C_6H_5CHO$), preventing further oxidation into benzoic acid.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Etard's reaction is a named organic oxidation reaction used to convert an aromatic methyl group directly into an aldehyde functional group.

Step 2: Key Formula or Approach:
The reaction involves the partial oxidation of toluene (or substituted toluenes) using a mild oxidizing agent, chromyl chloride (\( \text{CrO}_2\text{Cl}_2 \)), in the presence of a non-polar solvent like carbon tetrachloride (\( \text{CCl}_4 \)) or carbon disulfide (\( \text{CS}_2 \)).

Step 3: Detailed Explanation:
When toluene reacts with chromyl chloride, it forms a brown chromium complex as an intermediate.
The chemical reaction occurs as follows:
\[ \text{C}_6\text{H}_5\text{CH}_3 + 2\text{CrO}_2\text{Cl}_2 \rightarrow \text{C}_6\text{H}_5\text{CH(OCr(OH)Cl}_2)_2 \]
Subsequent acid hydrolysis of this brown complex cleaves it to yield the corresponding aromatic aldehyde, which is benzaldehyde.
\[ \text{C}_6\text{H}_5\text{CH(OCr(OH)Cl}_2)_2 \xrightarrow{\text{H}_3\text{O}^+} \text{C}_6\text{H}_5\text{CHO} \]
Since the oxidation stops at the aldehyde stage and does not proceed further to a carboxylic acid, the main product formed is benzaldehyde.

Step 4: Final Answer:
The product formed during Etard's reaction is Benzaldehyde.