Question

Which of the following sets of reagents convert toluene to benzaldehyde?

• A. $B, C, D$
• B. $A, C$
• C. $A, D$
• D. $B, D$

Hint:

To convert toluene to benzaldehyde, use selective oxidation methods such as the Etard reaction (CrO$_2$Cl$_2$) or controlled halogenation with Cl$_2$/hv, H$_2$O.

Answer 1

The Correct Option is C

Step 1: Identify the Reagents for Partial Oxidation
The conversion of toluene to benzaldehyde involves partial oxidation. The effective reagents for this reaction are:
- Chromyl chloride ($CrO_2Cl_2$) in CS$_2$, H$_3O^+$ (Etard reaction)
- Chlorine ($Cl_2$) in the presence of light and water Step 2: Explanation
- $A: Cl_2/ hv, H_2O, \triangle$ → Effective (Partial oxidation of toluene to benzaldehyde)
- $B: Cl_2/Fe; H_2O$ → Ineffective (Leads to benzoic acid)
- $C: KMnO_4/ OH^-; H^+$ → Ineffective (Complete oxidation to benzoic acid)
- $D: CrO_2Cl_2/CS_2; H_3O^+$ → Effective (Etard reaction forms benzaldehyde)
Thus, the correct answer is $A, D$. \bigskip