PhCHO + HCHO `overset("Conc.KOH")(rarr)`
Correct statement regarding reaction will be

Options

A. It is an example of redox reaction
B. H CHO is oxidised
C. It is cross cannizaro reaction
D. Ph–CHO is reduced

Answer

To solve the question regarding the reaction of benzaldehyde (PhCHO) and formaldehyde (HCHO) in the presence of concentrated KOH, we will analyze the reaction step by step.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- The reaction between benzaldehyde (PhCHO) and formaldehyde (HCHO) in the presence of concentrated KOH is known as the Cannizzaro reaction. This reaction occurs when aldehydes that do not have alpha-hydrogens undergo disproportionation.

**Hint**: Remember that Cannizzaro reactions typically involve aldehydes without alpha-hydrogens.

2. **Identifying Reactivity**:
- In this reaction, formaldehyde is more reactive than benzaldehyde due to the absence of resonance stabilization in formaldehyde. Therefore, KOH will preferentially attack formaldehyde.

**Hint**: Consider the stability of the resonance structures when comparing reactivity.

3. **Mechanism of the Reaction**:
- The hydroxide ion (OH⁻) from KOH attacks the carbonyl carbon of formaldehyde (HCHO), leading to the formation of an alkoxide intermediate (HCO⁻).
- This alkoxide can then undergo further reaction with benzaldehyde.

**Hint**: Focus on the nucleophilic attack of the hydroxide ion on the carbonyl carbon.

4. **Formation of Products**:
- The alkoxide from formaldehyde attacks the carbonyl carbon of benzaldehyde, resulting in the formation of a new alkoxide intermediate.
- This intermediate can then undergo protonation (hydrolysis) to yield an alcohol (from benzaldehyde) and a carboxylic acid (from formaldehyde).

**Hint**: Keep track of the oxidation states of the carbon atoms in the products.

5. **Final Products**:
- The final products of the reaction are:
- Benzyl alcohol (from benzaldehyde)
- Formic acid (from formaldehyde)

**Hint**: Identify the functional groups in the products to confirm their identities.

6. **Redox Nature of the Reaction**:
- In this reaction, formaldehyde is oxidized to formic acid, while benzaldehyde is reduced to benzyl alcohol. This indicates that the reaction is a redox reaction.

**Hint**: Remember that oxidation involves an increase in oxidation state, while reduction involves a decrease.

7. **Conclusion**:
- The correct statements regarding the reaction are:
- Formaldehyde is oxidized to formic acid.
- Benzaldehyde is reduced to benzyl alcohol.
- The reaction is a redox reaction.

**Hint**: Summarize the key transformations that occur in the reaction to identify the correct statements.

### Summary of Correct Statements:
- Formaldehyde is oxidized.
- Benzaldehyde is reduced.
- The reaction is a redox reaction.

### Final Answer:
All statements regarding the reaction are correct.