The addition of Hi to unsaturated hydrocarbons using I₂₊ and Al₂0₃

Previous investigators demonstrated that it is possible to iodinate arenes with iodine on dehydrated gamma alumina. This work focused on the hydroiodination of cyclic and acyclic alkenes using iodine and dehydrated gamma alumina. The mechanism of this addition of HI was also studied.

The results of this investigation show that cyclic alkenes such as cyclopentene, cyclohexene, cycloheptene, and cyclooctene react with I₂ on alumina to give the corresponding alkyl iodide. Acyclic such as 1-octene and alkynes such as 1-hexyne also react with I₂ on alumina to give iodinated products. The reaction involves the addition of HI to a carbon-to-carbon multiple bond and the addition takes place on the surface of the alumina. The reaction appears to proceed via a classical carbocation mechanism.