Question:medium

Identify the product of following reaction.
\(\text{Formaldehyde} + \text{Benzaldehyde} \xrightarrow[\text{H}_3\text{O}^+]{\text{conc. NaOH}} \text{product}\)

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Cannizzaro: aldehyde → alcohol + acid simultaneously.
Updated On: May 14, 2026
  • Phenyl methanol and methanol
  • Methanol and benzoic acid
  • Methanoic acid and phenyl methanol
  • Methanoic acid and benzoic acid
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The Correct Option is C

Solution and Explanation

Step 1: Understanding the Concept:
The reaction of aldehydes lacking \(\alpha\)-hydrogen atoms with concentrated alkali (\(\text{NaOH}\) or \(\text{KOH}\)) results in a disproportionation reaction called the Cannizzaro reaction. When two different aldehydes without \(\alpha\)-hydrogens are used, it is a crossed Cannizzaro reaction.
Step 2: Key Formula or Approach:
Identify the reaction type based on the reagents. In a crossed Cannizzaro reaction, the more reactive aldehyde (usually formaldehyde) gets oxidized to a carboxylic acid, and the less reactive one gets reduced to an alcohol.
Step 3: Detailed Explanation:
In a crossed Cannizzaro reaction involving formaldehyde (\(\text{HCHO}\)) and another non-enolizable aldehyde like benzaldehyde (\(\text{C}_6\text{H}_5\text{CHO}\)), the highly reactive formaldehyde is always oxidized to the corresponding carboxylic acid salt (formate), while the other aldehyde is reduced to the corresponding alcohol.
The reaction proceeds as follows: \[ \text{HCHO} + \text{C}_6\text{H}_5\text{CHO} \xrightarrow{\text{conc. NaOH}} \text{HCOO}^-\text{Na}^+ + \text{C}_6\text{H}_5\text{CH}_2\text{OH} \] The products formed in the basic medium are sodium formate and benzyl alcohol (phenyl methanol).
The subsequent step involves acidification (\(\text{H}_3\text{O}^+\)), which converts the formate salt into methanoic acid (formic acid): \[ \text{HCOO}^-\text{Na}^+ \xrightarrow{\text{H}_3\text{O}^+} \text{HCOOH} \] Therefore, the final isolated products are Methanoic acid (\(\text{HCOOH}\)) and Phenyl methanol (\(\text{C}_6\text{H}_5\text{CH}_2\text{OH}\)).
Step 4: Final Answer:
The products are methanoic acid and phenyl methanol.
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