Which of the following arrangements with respect to their reactivity in nucleophilic addition reaction is correct?
- acetophenone < benzaldehyde < p-tolualdehyde < p-nitrobenzaldehyde
- acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde
- p-nitrobenzaldehyde < benzaldehyde < p-tolualdehyde < acetophenone
- benzaldehyde < acetophenone < p-nitrobenzaldehyde < p-tolualdehyde
Answer
(2) acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde
Solution
Reactivity + on carbonyl C, less crowding.
Ketone (acetophenone): two groups, more hindrance least reactive.
-CH3 (+I, hyperconjugation) lowers +; -NO2 (-I,-M) raises it.
acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde
Answer: (2)