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Question
Arrange the following compound in increasing order of its reactivity in nucleophilic addition reactions.
Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.
Hint: Consider steric effect and electronic effect.
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Solution
- The +I effect is more in ketones than in aldehydes. Hence, acetophenone is the least reactive in nucleophilic addition reactions.
- Among aldehydes, the +I effect is the highest in p-tolualdehyde because of the presence of the electron-donating −CH3 group and the lowest in p-nitrobezaldehyde because of the presence of the electron-withdrawing −NO2 group.
- Hence, the increasing order of the reactivities of the given compounds is:
Acetophenone < p-Tolualdehyde < Benzaldehyde < p-Nitrobenzaldehyde
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