Involvement of Neighboring Chlorine in the Exchange Reactions of Iodine Monochloride and Vicinal Organic Iodochlorides

Article abstract of DOI:10.1021/jo00170a026

The reaction of vicinal organic iodochlorides and ICl in CCl4 at 25 deg C forms vicinal organic dichlorides and iodine.The rate law for this exchange reaction of ICl and 2-chloro-3-iodo-2,3-dimethylbutane is overall third order: second order in ICl and first order in iodochloride with a value of k₃ = 7.2 +/- 0.9 M^-2s^-1.Stereospecific exchange occurs in the reaction ICl and erythro- and threo-2-chloro-3-iodobutane.Thus the erythro isomer forms only meso-2,3-dichlorobutane while the threo isomers form only the dl dichloride.Nonstereospecific exchange occurs in the reaction of ICl and erythro- and threo-1-chloro-2-iodo-1-phenylpropane.The data support a mechanism involving a cationic intermediate.In addition, the chlorine atom is involved in the reaction prior to the product-determining step.