Question

The relative reactivities of acyl compounds towards nucleophilic substitution are in the order of:

• A. acid anhydride > amide > ester > acyl chloride
• B. acyl chloride > ester > acid anhydride > amide
• C. acyl chloride > acid anhydride > ester > amide
• D. ester > acyl chloride > amide > acid anhydride

Answer 1

Answer: (C)

acyl chloride > acid anhydride > ester > amide

${}^{\prime }Acylchloride>Acidanhydride>Ester>Amide$

The ease of nucleophilic substitution is depended upon the nature of leaving the group. When the leaving tendency of a group in a comp is, high, then the compound is more reactive, towards nucleophilic substitution.

The nucleophilic acyl substitution is completed in $2$ step;

The reactivity of the compound may be explained on the basicity of leaving the group. A weaker base is a better leaving group.

The order of bascity is as;

$C{l}^{-}<RCO{O}^{-}<R{O}^{-}<N{H}_2^{-}$

Hence order of leaving tendency is $C{l}^{-}>RCO{O}^{-}>R{O}^{-}>N{H}_2^{-}$ and therefore the order of reactivity of acyl compound is as;

$Acylchloride>AcidAnhydride>Ester>Amide$.

Option 'c' is answer.