​​Arrange these compounds in decreasing order of reactivity for nucleophilic addition reaction :
a) C6H5CHO
b) CH3CHO
​c) CH3COCH3
​d) C6H5COC6H​5
 

Dear Student,

Nucleophiles attack on electron deficient centres. Lesser the electron density, greater will be reactivity towards nucleophilic addition reaction. 
Aromatic carbonyl groups are less electrophilic than their corresponding aliphatic alkanes. This is due to electron donating effect of the benzene ring which decreases positive charge on carbon of the carbonyl group making it less susceptible to nucleophilic attack. 
Therefore, (b) and (c) are more reactive than (a) and (d).
Now, ketones are less reactive than aldehydes, as in ketones two -R groups are present which makes the carbonyl C less electrophilic in comparison to aldehydes which have only one -R group. Also, due to steric factor, attack on ketones is difficult than aldehydes. 
Therefore, (b) is more reactive than (c) and (a) is more reactive (d). 
Therefore, the decreasing order of reactivity for nucleophilic addition reaction is : 
(b) > (c) > (a) > (d)
 

  • 0
What are you looking for?