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Theoretical study of the iodination of methoxybenzene by iodine monochloride
Author(s) -
Wei Yu,
Wang BingWu,
Hu ShaoWen,
Chu TaiWei,
Tang LingTian,
Liu XinQi,
Wang Yi,
Wang XiangYun
Publication year - 2005
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.911
Subject(s) - chemistry , iodine monochloride , halogenation , natural bond orbital , electrophile , computational chemistry , medicinal chemistry , solvent , density functional theory , iodine , organic chemistry , catalysis
The pathway of the iodination of methoxybenzene by electrophilic iodine monochloride (ICl) was studied by using density functional theory (DFT) calculations at the B3LYP/6–311G* and MP2/6–311G*//B3LYP/6–311G* levels. The iodination occurs in the position para to the methoxy group, and proceeds in two steps. Initially, a π‐complex forms between ICl and aromatic ring of methoxybenzene. With a barrier of 60.81 kcal mol −1 (1 kcal = 4.184 kJ), the π‐complex can be activated to an intermediate σ‐complex with energy 42.02 kcal mol −1 higher than that of the π‐complex. The σ‐complex then transforms easily (barrier 3.56 kcal mol −1 ) into the final products, 1‐iodo‐4‐methoxybenzene and HCl. The total iodination is slightly exothermic. Accompanying to the ICl bond breaking and CI bond formation, a hydrogen atom migrates first to iodine and then to chlorine. According to NBO charge, Wiberg bond index and molecular orbital analysis, both charge separation and charge transfer occur during the iodination. Solvent effects were examined with the IEFPCM method and the B3LYP/6–311G* level. The results imply that polar solvents should play a key role in lowering the energy barrier, and favor the ion‐pair route of the iodination reaction. Copyright © 2005 John Wiley & Sons, Ltd.