question_answer

Which one of the following compounds is most reactive towards nucleophilic addition?

A)  \[C{{H}_{3}}CHO\]                         

B)  \[PhCOC{{H}_{3}}\]

C)  \[PhCOPh\]                      

D)  \[C{{H}_{3}}COC{{H}_{3}}\]

Correct Answer: A

Solution :

                 Carbonyl compounds undergoes nucleophilic addition reaction. [Y- shows negative inductive effect] If group or atom attached with carbonyl carbon shows negative inductive effect, then it decreases electron density on carbonyl carbon and facilitate the attack of nucleophiles, hence reactivity of carbonyl compound increases.  [Y-shows negative inductive effect] If group or atom attached with carbonyl carbon shows positive inductive effect, then it increases electron density on carbonyl carbon and suppress the attack of nucleophiles, hence, reactivity of carbonyl compound decreases. The aromatic aldehydes and ketones are less reactive than their aliphatic analogues. This is due to the -R effect of benzene ring. On the basis of above informations, the increasing order of the nucleophilic addition reaction in the following compound will be\[C{{H}_{3}}CHO>C{{H}_{3}}COC{{H}_{3}}>PhCOC{{H}_{3}}>PhCOPh\]