The compound obtained when acetaldehyde reacts with dilute aqueous sodium hydroxide exhibits

Options

A. Geometrical isomerism
B. Optical isomerism
C. Neither optical nor geomtrical isomerism
D. Both optical and geometrical isomerism

Explanation

To solve the question regarding the compound obtained when acetaldehyde reacts with dilute aqueous sodium hydroxide, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
The reactant in this case is acetaldehyde, which has the chemical formula CH₃CHO.

2. **Understand the Reaction**:
When acetaldehyde reacts with dilute aqueous sodium hydroxide (NaOH), it undergoes an aldol condensation reaction. This reaction involves the formation of an enolate ion from acetaldehyde.

3. **Formation of the Enolate Ion**:
The sodium hydroxide deprotonates the hydrogen atom on the alpha carbon (the carbon adjacent to the carbonyl group) of acetaldehyde, leading to the formation of an enolate ion:
\[ CH₃CHO \xrightarrow{NaOH} CH₂=C(OH)CH₃ \]

4. **Nucleophilic Attack**:
The enolate ion then acts as a nucleophile and attacks another molecule of acetaldehyde. This results in the formation of a β-hydroxy aldehyde (specifically, 3-hydroxybutanal):
\[ CH₂=C(OH)CH₃ + CH₃CHO \rightarrow CH₃CH(OH)CH₂CHO \]

5. **Formation of the Aldol Product**:
The product formed is a β-hydroxy aldehyde, which can be represented as:
\[ CH₃CH(OH)CH₂CHO \]

6. **Chirality and Isomerism**:
The β-hydroxy aldehyde has one chiral center (the carbon attached to the hydroxyl group and the aldehyde group). The presence of a chiral center means that the compound can exhibit optical isomerism.

7. **Conclusion**:
Since the compound formed has a chiral center, it exhibits optical isomerism. Therefore, the correct answer to the question is that the compound obtained when acetaldehyde reacts with dilute aqueous sodium hydroxide exhibits optical isomerism.

### Final Answer:
The compound obtained when acetaldehyde reacts with dilute aqueous sodium hydroxide exhibits **optical isomerism**.

---