Radioactive contamination
Some organs concentrate certain elements and hence radionuclide variants of those elements. This action may lead to much lower removal rates. For instance, the thyroid gland takes up a large percentage of any iodine that enters the body. Large quantities of inhaled or ingested radioactive iodine may impair or destroy the thyroid, while other tissues are affected to a lesser extent. Radioactive iodine-131 is a common fission product; it was a major component of the radioactivity released from the Chernobyl disaster, leading to nine fatal cases of pediatric thyroid cancer and hypothyroidism. On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid's selective uptake of iodine.
Carbonyl oxidation with hypervalent iodine reagents
The mechanism of carbonyl oxidation by iodine(III) reagents varies as a function of substrate structure and
reaction conditions, but some generalizations are possible. Under basic conditions, the active iodinating species are iodine(III) compounds in which any relatively acidic ligands on iodine (such as acetate) have been replaced by alkoxide. In all cases, the α carbon forms a bond to
iodine. Reduction of iodine(III) to iodine(I) then occurs via attack of a nucleophile on the now electrophilic α
carbon. Under basic conditions, nucleophilic attack at the carbonyl carbon is faster than attack at the α carbon. Iodine
displacement is actually accomplished intramolecularly by the carbonyl oxygen, which becomes the α-hydroxyl oxygen in the
product.