1900

Free Radicals

Moses Gomberg (1866–1947)

Most of the molecules described in this book have all their electrons accounted for. A typical single bond is the sharing of two electrons, one from each atom involved, with no odd ones left over. Or are there? In 1900, Russian-born chemist Moses Gomberg reported the first known exception. He was the first chemist to make tetraphenylmethane, the compound with a single carbon atom sprouting four aromatic rings. Along the way, he naturally had several triphenylmethyl intermediates, and he noticed some odd reactivity when he tried to couple them head-to-head to make his desired product. He had apparently formed some sort of triphenylmethyl species that was air sensitive, and it quickly reacted with chlorine, bromine, and iodine, among other compounds. This was not triphenylmethane—Gomberg had plenty of that around, and it was not air sensitive at all. The reactivity of his new product didn’t match up with any known species, and Gomberg made the bold suggestion that he had produced and isolated the first organic free radical, whose unpaired electron made it highly reactive.

Some chemists were convinced, but many others were not. Over the next thirty years, though, evidence began to pile up from other labs that free radicals were intermediates in many reactions, and that they could be stabilized by such things as multiple phenyl groups. Gomberg is now recognized as the founder of free radical chemistry.

Free radicals often get a bad rap in health-related reporting, as they can contribute to illnesses related to aging, heart attacks, stroke, and inflammation. However, living cells produce many free radicals through their use of oxygen, among them superoxide, and free radicals play important positive roles in metabolism and in fighting disease. For example, white blood cells use free radicals to destroy cells infected with bacteria or viruses.

Gomberg is also remembered for being perhaps the last chemist to try to invoke a nineteenth-century-style “gentleman’s agreement” for research priority. At the end of his first triphenylmethyl radical paper, he said, “This work will be continued and I wish to reserve the field for myself.” It didn’t happen.

Microcrystals of Vitamin C, an antioxidant that inhibits the production of free radicals, in polarized light.