Summary Di-o-tolyliodonium iodide decomposes at 155'into o-iodotoluene and not into a mixture of iodotoluenes. The nature of the reaction product indicates that the ditolyliodonium ion splits into o-iodotoluene and positively charged o-tolyl ion by a scission of the CI bond. The combining of this ion with the negative iodide ion produces o-iodotoluene.