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A team of chemists from Scripps Research and Abbvie Process Research and Development has found that making a couple of minor changes to Kolbe coupling allows for easily making high-cost materials out of low-cost materials or even waste products. Their study is reported in the journal Science. Peng Guo and Ke-Yin Ye, both with Fuzhou University, in China, have published a Perspective piece in the same journal issue outlining the work by the team on this this effort.

Kolbe coupling was first described by Michael Faraday back in 1834, but it was not well known until Hermann Kolbe used it in 1849 to couple pairs of molecules in a substance containing a carboxylic acid. Thus, it bears his name. It is currently considered to be one of the oldest known reactions in organic chemistry.

The reaction occurs when a platinum electrode is inserted into the mix and electricity applied. Thus, the reaction is sometimes referred to as Kolbe electrolysis. It also results in the release of carbon dioxide. But the reaction usually has other unfortunate outcomes, as well, such as oxidizing other materials in the mix, which is why it is rarely used. In this new effort, the research team was studying decarboxylation for another project when they found they had made adjustments to Kolbe coupling, and found that doing so provided unexpected benefits.

In their work, the researchers had been using rapid alternating polarity (rAP) in their work, which they applied to the new effort. Also, instead of using platinum electrodes, they were using electrodes that were carbon-based. They noted that because they were using rAP, oxidizing of functional groups was avoided.

Intrigued by their finding, the team conduced Kolbe coupling experiments with the two adjustments. They bought a bottle of castor oil and used it to make 10-undecenoic acid. They then inserted an electrode and conducted rAP. The ensuing reaction produced 1,19-eicosadiene, a material that typically costs approximately $10,000 per gram.

Next, the group produced diol, which they mixed with a diketone to create a degradable ketal-polymer. They suggest that it could also be used to convert side-chain carboxylic acids to other products or perhaps to convert succinic acid esters into adipic acid esters.

More information: Yuta Hioki et al, Overcoming the limitations of Kolbe coupling with waveform-controlled electrosynthesis, Science (2023). DOI: 10.1126/science.adf4762

Peng Guo et al, Alternating the current direction, Science (2023). DOI: 10.1126/science.adh1837

Journal information: Science

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Original post:

Adjustment to Kolbe coupling allows one to make high-cost materials out of waste - Phys.org