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Question
Give the decreasing order of nucleophilic addition reaction of the followings:
(i) HCHO
(ii) PhCHO
(iii) Chloral (Cl3C−CH=O)
(iv) Acetophenone
Give the decreasing order of nucleophilic addition reaction of the followings:
(i) HCHO
(ii) PhCHO
(iii) Chloral (Cl3C−CH=O)
(iv) Acetophenone
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Solution
The correct option is A (iii) > (i) > (ii) > (iv)
Aldehydes are more reactive towards nucleophilic substitution compared to ketones because of less steric hindrance and electronic factors. In Aldehydes electron withdrawing group increase its reactivity by making the carbonyl carbon more electrophilic.
Here, CCl3− is an electron withdrawing group. So, it increases reactivity.
Thus, (iii) have highest reactivity toward addition reaction.
HCHO has very less steric hindrance.
Ph−CHO is bulkier and the cabonyl carbon is less electrophilic due to resonance with benzene.
Acetophenone is bulkier ketone. Hence, it is least reactive.
Hence, the decreasing order of nucleophilic addition reaction is
CCl3−CHO>HCHO>Ph−CHO>Ph−CO−CH3
Aldehydes are more reactive towards nucleophilic substitution compared to ketones because of less steric hindrance and electronic factors. In Aldehydes electron withdrawing group increase its reactivity by making the carbonyl carbon more electrophilic.
Here, CCl3− is an electron withdrawing group. So, it increases reactivity.
Thus, (iii) have highest reactivity toward addition reaction.
HCHO has very less steric hindrance.
Ph−CHO is bulkier and the cabonyl carbon is less electrophilic due to resonance with benzene.
Acetophenone is bulkier ketone. Hence, it is least reactive.
Hence, the decreasing order of nucleophilic addition reaction is
CCl3−CHO>HCHO>Ph−CHO>Ph−CO−CH3
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