Boosted molecular mobility during common chemical reactions

Elements of speed

30 November 2020

Chemical reactants regularly move through solvents far faster than normal diffusion would permit.

Typical ‘Brownian’ motion describes the regular diffusion of particles or chemicals through a solvent due to the buffeting effect of surrounding solvent molecules. But chemical reactants have been observed to exceed Brownian diffusion speeds under some special circumstances, such as enzyme biocatalysis.

Now, a team that included researchers from the Institute for Basic Science in South Korea has shown that such chemical speeding can also occur in a range of common chemical reactions.

Using a nuclear magnetic resonance technique to observe 15 well-known reactions, the researchers observed several reactions — including catalysed bimolecular reactions, ring-opening metathesis polymerization and Sonogashira coupling — that involved a speed boost.

The phenomenon is probably due to the energy released by the reaction, causing broad-scale perturbation to the structure of solvent molecules surrounding the reactants. The results provide new insights into the conversion of chemical activity into mechanical motion.

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References

1. Science 369, 537–541 (2020). doi: 10.1126/science.aba8425