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Q.
The order of compounds in their reactivity towards $ HCN $ is
AMUAMU 2014Aldehydes Ketones and Carboxylic Acids
Solution:
As the number/ size of alkyl group attached to the carbonyl carbon increases, their reactivity towards $HCN$ (addition-elimination reaction) decreases due to steric hindrance
Hence, the order of reactivity of different compounds towards $HCN$ is
di tert-butyl ketone < methyl tert-butyl ketone < acetone < acetaldehyde
or $[(CH_{3})_{3}C]_{2} C =O < (CH_{3})_{3}CCOCH_{3}< CH_{3}COCH_{3}< CH_{3}CHO$