Which of the following substituents exerts the strongest electron-withdrawing inductive effect when attached to a carbon atom?
- -F
- -OH
- -NH₂
- -NO₂ (correct answer)
Explanation: The strength of the inductive effect is related to electronegativity and formal charge. The nitro group, -NO₂, contains a nitrogen atom with a formal positive charge bonded to two highly electronegative oxygen atoms. This combination creates a very powerful pull on electrons in the sigma bond, making it an exceptionally strong inductive electron-withdrawing group. While fluorine (A) is the most electronegative single atom, the overall effect of the positively charged nitrogen in the nitro group is stronger. Oxygen (in -OH) and nitrogen (in -NH₂) are less electronegative than fluorine, resulting in weaker inductive effects.