Abstract: This paper explores the “Iodine-Catalyzed Chlorination Reaction of Chlorobenzene”, a topic derived from a question in the 2021 National College Entrance Examination chemistry paper for Zhejiang, which embodies a myriad of fundamental chemical concepts and theories. Previous work has delved into this topic, yet their findings diverged from the descriptions provided in the exam paper. Utilizing Density Functional Theory (DFT) calculations, this study conducts a comprehensive reexamination of the reaction, identifying the catalytically active component and its formation mechanism. It elucidates the molecular mechanisms, thermodynamics, and kinetics of the chlorination reaction of chlorobenzene, evaluates the reactivity of ortho, meta, and para substitutions, and investigates the impact of electronic and steric effects on the reactivity. The computational results align with the description in the exam paper, affirming the question’s precision and scientific accuracy. The insights gained from this research significantly contribute to students’ deeper understanding of electrophilic aromatic substitution reactions in aromatic compounds.

Key words: Chlorobenzene, Chlorination, Iodine, Reaction Mechanism, Computation Chemistry