Question

Which of the following reagents can be used to prepare benzaldehyde from toluene?

• A. $ Cr{{O}_{3}} $ in $ {{(C{{H}_{3}}CO)}_{2}}O $
• B. $ {{K}_{2}}C{{r}_{2}}{{O}_{7}} $ + cone. $ {{H}_{2}}S{{O}_{4}} $
• C. Hot alkaline $ KMn{{O}_{4}} $
• D. Conc. $ HN{{O}_{3}} $

Answer 1

Answer: (A)

$ {{k}_{2}}C{{r}_{2}}{{O}_{7}}+conc.\,{{H}_{2}}S{{O}_{4}}, $ hot alkaline $ KMn{{O}_{4}} $ and cone. $ HN{{O}_{3}} $ will all oxidise toluene to benzoic acid while $ Cr{{O}_{3}} $ in $ {{(C{{H}_{3}}CO)}_{2}}O $ will oxidise toluene to only benzaldehyde.