Which of the following statements about benzaldehyde is/are true?

Options

A. Reduces Tollens' reagent
B. Undergoes aldol condensation
C. Undergoes cannizzaro reaction
D. Does not form an addition compound with sodium hydrogen sulphite

Answer

To determine which statements about benzaldehyde are true, let's analyze each statement step by step.

1. **Statement 1: Benzaldehyde is an aromatic aldehyde.**
- Benzaldehyde (C6H5CHO) is indeed classified as an aromatic aldehyde because it contains a benzene ring and the aldehyde functional group (-CHO). Therefore, this statement is **true**.

2. **Statement 2: Benzaldehyde reduces Fehling's reagent.**
- Fehling's reagent is used to test for reducing sugars and aldehydes. However, benzaldehyde does not reduce Fehling's reagent because it lacks an alpha hydrogen. Thus, this statement is **false**.

3. **Statement 3: Benzaldehyde can reduce Tollens' reagent.**
- Tollens' reagent is a mild oxidizing agent that can oxidize aldehydes to carboxylic acids. Benzaldehyde can indeed reduce Tollens' reagent, so this statement is **true**.

4. **Statement 4: Benzaldehyde undergoes aldol condensation.**
- Aldol condensation requires the presence of an alpha hydrogen atom adjacent to the carbonyl group. Benzaldehyde does not have an alpha hydrogen (as it is a simple aromatic aldehyde), so it cannot undergo aldol condensation. Therefore, this statement is **false**.

5. **Statement 5: Benzaldehyde undergoes Cannizzaro reaction.**
- The Cannizzaro reaction occurs with aldehydes that do not have alpha hydrogens. Since benzaldehyde has no alpha hydrogen, it can undergo the Cannizzaro reaction. Thus, this statement is **true**.

6. **Statement 6: Benzaldehyde does not form an addition compound with sodium hydrogen sulfite (NaHSO3).**
- Generally, aldehydes and methyl ketones do form addition compounds with sodium hydrogen sulfite. Since benzaldehyde is an aldehyde, it should form an addition compound with NaHSO3. Therefore, this statement is **false**.

### Summary of True Statements:
- Statement 1: True
- Statement 2: False
- Statement 3: True
- Statement 4: False
- Statement 5: True
- Statement 6: False

### Final Conclusion:
The true statements about benzaldehyde are:
- Benzaldehyde is an aromatic aldehyde.
- Benzaldehyde can reduce Tollens' reagent.
- Benzaldehyde undergoes Cannizzaro reaction.