MECHANISMS OF EXCHANGE REACTIONS BETWEEN ELEMENTARY IODINE AND AROMATIC IODIDES
The thermel exchange of elementary iodine with iodobenzene and with p- nitroiodobenzene has been studied in the solvents hexachlorobutadiene-1,3 and nitrobenzene. Two independent processes contribute to the rate. One process is the expected direct radical exchange between an iodine atom and a molecule of aromatic iodide. The rate constans for this process are not signicantly affected by change of solvent, but substitution with a pnitro group slows the rate somewhat. This effect of substitution is opposite to the direction usually predicted and observed for radical reactions. The other exchange process is second order is aromatic iodide and is usually zero order is iodine. Change of solvent from hexachlorobutadiene to nitrobenzene inhibits this process for iodobezene but accelerates it for p-nitroiodobenzene. When both aromatic iodides are present is a solution, the rate constant for the exchange process involving one molecule of each is greater than the rate constant for either process involving two identical molecules. We propose that this exchange process involves reversible formation of a diphenyliodonium iodine ion pair and rapid exchange of molecule iodine with the iodide portion of it. The proposed mechanism explains some peculiar observations reported previously on the exchange of iodobenzenes with sodium iodide. These aromatic iodides also decompose with formation of molecular iodine. The rates are erratic but seem to follow first- order kinetics when only one aromatic iodide is present. If both iodobenzene and p-nitroiodobenzene are present, an additional decomposition is ascribed to rearrangement of the diphenylodine and mono-substituted diphenpl. (auth)
- Research Organization:
- Columbia Univ., New York
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-12-012227
- OSTI ID:
- 4301387
- Journal Information:
- Journal of the American Chemical Society (U.S.), Vol. Vol: 80; Other Information: Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
EFFECTS OF SUBSTITUENTS ON THE RADICAL EXCHANGE REACTION BETWEEN BENZYL IODIDE AND IODINE
METHYL RADICAL PRODUCTION IN THE RADIOLYSIS OF HYDROCARBONS