Question

An organic compound with molecular formula C\(_7\)H\(_6\)O forms 2,4-DNP derivative, reduces Tollens’ reagent and gives Cannizzaro reaction. On vigorous oxidation it gives benzene-1,2-dicarboxylic acid. Identify the compound. Also write the reactions of the compound with 2,4-DNP and when it undergoes Cannizzaro reaction.

Hint:

Cannizzaro reaction → Aldehydes without α-hydrogen. Tollens’ positive → Aldehyde confirmed.

Answer 1

Step 1: Interpret given tests.

• Forms 2,4-DNP derivative → Contains carbonyl group
• Reduces Tollens’ reagent → Aldehyde
• Undergoes Cannizzaro reaction → Aromatic aldehyde without α-H

Step 2: Molecular formula analysis. C\(_7\)H\(_6\)O suggests benzaldehyde derivatives.
Step 3: Oxidation clue. On vigorous oxidation gives benzene-1,2-dicarboxylic acid (phthalic acid). This implies an ortho-substituted aldehyde. Hence compound is: \[ \text{o-Hydroxybenzaldehyde (Salicylaldehyde)} \]
Reaction with 2,4-DNP: \[ \text{Aldehyde} + \text{2,4-DNP} \rightarrow \text{Orange precipitate (hydrazone)} \] \[ C_6H_4(OH)CHO + 2,4\text{-DNP} \rightarrow \text{2,4-DNP hydrazone} \]
Cannizzaro Reaction: In presence of strong base: \[ 2ArCHO \xrightarrow{NaOH} ArCH_2OH + ArCOONa \] For salicylaldehyde: \[ 2C_6H_4(OH)CHO \xrightarrow{NaOH} C_6H_4(OH)CH_2OH + C_6H_4(OH)COONa \]
Final Answer: \[ \text{Compound = o-Hydroxybenzaldehyde (Salicylaldehyde)} \]