In the given reactions, identify the reagent A and reagent B. [figure]
- A - CrO3 B - CrO3
- A - CrO3 B - CrO2Cl2
- A - CrO2Cl2 B - CrO3
- A - CrO2Cl2 B - CrO2Cl2
Answer
(2) A - CrO3 B - CrO2Cl2
Solution
Route A — chromic oxide in acetic anhydride (benzylidene diacetate, then hydrolysis):
C6H5CH3 [273-283 K]CrO3, (CH3CO)2O C6H5CH(OCOCH3)2
H3O+, C6H5CHO
Route B — chromyl chloride in CS2 (Étard reaction, chromium complex, then hydrolysis):
C6H5CH3 CrO2Cl2, CS2 C6H5CH(OCrOHCl2)2
H3O+ C6H5CHO
∴ A = CrO3, B = CrO2Cl2
Answer: (2)