JEE Mains Chemistry question is in the image
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Answer:
For a nucleophilic addition reaction to happen, it needs a carbon atom having a slight amount of positive charge. That is if carbon acts as an electron deficit center, nucleophilic addition reaction takes place at a faster rate.
According to the question, aromatic aldehydes or ketones act less reactive than aliphatic or straight chain compounds, hence they are less reactive towards NAR (Due to +R effect.).
When it comes to Ethanal and Propanone, the substitutents act as +I groups. Due to this, they make carbon center more negative as +I groups are usually Electron donating groups (EDG).
Hence more +I groups ⇒ Lower rate of NAR
According to the question, Ethanal has one +I group while Propanone has two +I groups. Hence due to lesser number of +I groups, Ethanal would be more reactive than Propanone.
Hence Option C, Ethanal is the right answer.
(Complete reactivity order is: C > D > B > A)