DIRECT POLYIODINATION OF BENZENESULFONIC ACID

Direct aromatic polyiodination of benzenesulfonic acid (using I2 and H5IO6 in H2SO4 at room temperature) was performed to test the possible intermediacy of C6H5SO3H in the corresponding direct polyiodination of benzene to C6H2I4. The major product from C6H5SO3H was 3,4,5-triiodobenzenesulfonic acid (4). In contrast, no 4 was formed in the C6H6 reaction, showing that no significant sulfonation of C6H6 to C6H5SO3H occurred during benzene iodination. Compound 4 itself was shown to be inert under the reaction conditions. A pathway is proposed from C6H5SO3H to the other reaction products (C6I6, C6I5H, two C6I4H2 isomers, and 3,4,5-triiodophenol), which therefore avoids the intermediacy of 4.