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In 1898, Moses Gomberg appears to have made crystals containing triphenylmethyl cations without recognizing their significance. A recent historical reinterpretation argues that these were an earlier instance of trivalent carbon—but they were not the triphenylmethyl radicals he proposed in 1900. That distinction makes the story more precise: Gomberg’s landmark radical discovery came later, after experiments meant to produce a different compound.
What Gomberg appears to have made in 1898
A 2026 paper, “Gomberg’s Earlier ‘Instance of Trivalent Carbon’,” reexamines an experiment from 1898. Its abstract says Gomberg believed he had produced a molecular complex of bromotriphenylmethane and two neutral iodine molecules. The authors instead identify the material as a mixture of three persistent single crystals of the triphenylmethyl cation. They argue that Gomberg had made trivalent-carbon compounds before he recognized them. Read the 2026 article abstract in JACS.
This is a modern reinterpretation of the earlier experiment, not evidence that Gomberg had already isolated the radical associated with his later discovery. The cation and radical are distinct species, and the abstract does not establish further experimental details about the 1898 crystals.
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What he discovered in 1900
Gomberg’s better-known work began as an attempt to synthesize hexaphenylethane. According to the American Chemical Society’s historical account, he first treated triphenylmethyl halides with sodium in benzene and then tried silver. The experiments produced a white crystalline powder that reacted with oxygen. He next combined triphenylmethyl chloride and zinc under carbon dioxide to limit oxidation. After removing the benzene, he obtained a highly reactive white solid that oxidized rapidly in air and reacted with halogens, including iodine. The product’s behavior did not fit the expected hexaphenylethane, leading him to infer a free radical. The ACS landmark booklet recounts the experiments.
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On November 1, 1900, Gomberg published “An Instance of Trivalent Carbon: Triphenylmethyl” in volume 22, issue 11 of the Journal of the American Chemical Society, pages 757–771. ACS notes that he also published in German that year. The JACS publication record gives the paper’s bibliographic details.
Why “trivalent carbon” mattered
In triphenylmethyl radical, a central carbon is bonded to three phenyl groups and has one unpaired electron. “Trivalent” describes its three bonds; it does not mean the carbon is a different element. The radical’s unpaired electron made its apparent persistence surprising to chemists accustomed to the idea that carbon formed four bonds.
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Gomberg described the material as persistent but not inert: “The radical so formed is apparently stable, for it can be kept both in solution and in the dry crystalline state for weeks.” The same historical account says the substance reacted readily with oxygen and halogens. Its persistence meant it could last under suitable conditions, not that it was unreactive.
Why the radical’s acceptance took time
ACS reports that Gomberg’s radical interpretation remained disputed for nearly a decade. Free radicals did not enter mainstream organic chemistry until the 1930s, as chemists continued to work through the implications of a carbon-centered species that did not fit the prevailing four-bond picture. The controversy belongs to the 1900 radical claim; it should not be confused with the newer interpretation of the 1898 cation crystals.
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There was another complication in the chemistry. Triphenylmethyl radicals can dimerize, and the product was long assigned a hexaphenylethane structure. A 2025 review in Chemical Society Reviews describes how Gomberg initially favored the correct quinoidal dimer structure, but the hexaphenylethane proposal was accepted for a long period. NMR established the correct structure in 1968. This structural correction is separate from the question of what Gomberg made in 1898. See the 2025 review on stable π-radicals.
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