Question

The synthesis of crotonaldehyde from acetaldehyde is an example of ...... reaction.

• A. nucleophilic addition
• B. elimination
• C. electrophilic addition
• D. nucleophilic addition-elimination

Hint:

Aldol condensation: first nucleophilic addition to carbonyl, then elimination of water gives conjugated aldehyde/ketone.

Answer 1

The Correct Option is D

Step 1: Identify the reaction.
Crotonaldehyde is formed by aldol condensation of acetaldehyde.
\[ 2CH_3CHO \rightarrow CH_3CH=CHCHO + H_2O \]
Step 2: Explain mechanism.
Aldol condensation involves:
- nucleophilic addition of enolate ion to carbonyl carbon
- followed by elimination of water to form \(\alpha,\beta\)-unsaturated aldehyde
Step 3: Conclusion.
Thus it is nucleophilic addition followed by elimination.
Final Answer:
\[ \boxed{\text{nucleophilic addition-elimination}} \]