Which atom in toluene sulfonyl chloride (TsCl) is electrophilic? Justify your answer.

(i) C because the pi-system of the ring withdraws electrons, making it electron-deficient.

(ii) S because it is surrounded by electron-withdrawing groups, making it electron-deficient.

(iii) O because it can form resonance and has a negative charge, making it electron-rich.

(iv) Cl because it is the most electronegative atom, making it an electron-rich species.