Arrange the following compounds in order of increasing reactivity towards HCN :
Acetaldehyde, Acetone, Di-tertiary butyl ketone, Methyl tertiary butyl ketone.

Explanation

To determine the order of increasing reactivity towards HCN for the given compounds (Acetaldehyde, Acetone, Di-tertiary butyl ketone, and Methyl tertiary butyl ketone), we need to consider the concept of steric hindrance. The more steric hindrance present around the carbonyl carbon, the less reactive the compound will be towards nucleophiles like HCN.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- Acetaldehyde: CH₃CHO
- Acetone: CH₃C(=O)CH₃
- Di-tertiary butyl ketone: (C(CH₃)₃)C(=O)(C(CH₃)₃)
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