1965 Volume 38 Issue 10 Pages 1590-1595
Four isomeric diiodo-m-xylenes have been synthesized and their isomerization in concentrated acids investigated in order to elucidate the mechanism of the new rearrangement observed in the Jacobsen reaction of 2-iodo-m-xylene. 2,4- and 4,5-Diiodo-m-xylene, in the presence of cold sulfuric or hot polyphosphoric acid, isomerize to 4,6- and 2,5-diiodo-m-xylene respectively. All four isomers readily undergo disproportionation with hot sulfuric acid to give mixtures of tri- and tetraiodo-m-xylenes. No disproportionation has been observed in the reaction with polyphosphoric acid. The important role played by a sulfo group in this reaction has been discussed.
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