See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

**Understanding the -I Effect:** The -I (inductive) effect refers to the withdrawal of electron density through the σ-bond framework. Groups that pull electron density away from a benzene ring (or any carbon atom) show a negative inductive effect. **Analysis of each group:** - **(A) $-NH_3^+$**: The positive charge on nitrogen makes it highly electron-withdrawing through the σ-bond, showing strong -I effect. - **(B) $-NH_2Me^+$**: One methyl group on nitrogen slightly reduces the positive charge density compared to $-NH_3^+$, weakening the -I effect. - **(C) $-NMe_2^+$**: Two methyl groups on nitrogen further dilute the positive charge density and increase steric hindrance around nitrogen, making the positive charge less effective at withdrawing electrons. Additionally, the methyl groups are electron-donating (alkyl groups show +I effect), which opposes and reduces the overall -I effect of the positively charged nitrogen. - **(D) $-NMe_3^+$**: Three methyl groups create even more steric crowding and greater +I contribution from the alkyl groups, further reducing the net -I effect. **Conclusion:** $-NH_3^+$ has the maximum -I effect because the nitrogen atom bears the full positive charge with no electron-donating alkyl groups to counteract it, allowing maximum electron withdrawal through the σ-bond. **The answer is (A), not (C).**