Arrange the following in increasing order of their reactivity towards HCN:
Di-tert. butyl ketone, Acetaldehyde, Acetone
Di-tert. butyl ketone, Acetaldehyde, Acetone
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Solution and Explanation
Step 1: Understanding the Concept:
The nucleophilic addition of \(HCN\) to carbonyl compounds depends on two factors:
1. Steric hindrance: Bulkier groups around the carbonyl carbon slow down the attack of the nucleophile.
2. Electronic factors: Electron-releasing alkyl groups reduce the electrophilicity (positive charge) of the carbonyl carbon.
Step 2: Detailed Explanation:
- Acetaldehyde (\(CH_3CHO\)): It is an aldehyde with only one methyl group and one hydrogen. It has the least steric hindrance and highest electrophilicity.
- Acetone (\(CH_3COCH_3\)): It is a ketone with two methyl groups. It has more steric hindrance and lower electrophilicity than acetaldehyde due to two \(+I\) groups.
- Di-tert. butyl ketone (\(((CH_3)_3C)_2CO\)): It has two extremely bulky tert-butyl groups. Steric hindrance is maximum here, making it the least reactive.
Step 3: Final Answer:
Order: Di-tert. butyl ketone \(<\) Acetone \(<\) Acetaldehyde.
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