Organic Chemistry : Identifying Electron-Withdrawing Groups

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

Example Question #22 : Nucleophiles And Electrophiles

Which of the following R groups would increase the rate of the following substitution reaction?


Possible Answers:

Correct answer:


The above reaction would more readily proceed if the electrophilicity of the carbonyl carbon were enhanced. This may be achieved through electron withdrawal via the R group.

The ether (-OMe), the methyl (-Me), and the hydroxyl (-OH), would all produce a electron-donating effect, and are thus incorrect answers.

The nitro group (-NO2), and the positively charged, tetra-substituted amino group (consider the structure once this trimethyl amino group is connected to the aryl ring) are both electron-withdrawing. As the trimethyl amino group will have an overall positive charge (and the nitro group is neutral overall), the trimethyl amino group is the stronger electron-withdrawing moiety, and is thus the correct answer.

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