Ground-breaking solvent research by Professor Benjamin Schwartz’s group was recently highlighted by the Department of Energy (DOE) Office of Science.
Schwartz and graduate student Devon Widmer (pictured right) reported on the highlighted research in their 2018 Nature Chemistry paper.
A professor of physical chemistry at UCLA, Schwartz is Senior Editor of the Journal of Physical Chemistry. Widmer, a science writer, is a graduate student in Schwartz’s group.
Widmer explained their research – “The world we experience in our daily lives is a macroscopic landscape full of tangible, solid objects. And that’s the way we like it. Fortunately, we rarely need to concern ourselves with the intangible world of chemistry, the complex quantum-scale processes underlying our macroscopic world. Unless you’re a chemist studying fundamental chemical processes. I happen to be a chemist studying fundamental chemical process. But based on studies of simple molecules in solution, the interactions between the molecules necessary for life and the liquid solvents permeating our squishy, fluid-filled bodies may play a key role in keeping us alive. At the very least, these solute-solvent interactions, even when quite weak, can dramatically affect the behavior of that solute. Indeed, the answer to questions about why certain biological processes occur in the body may well lie in the way solutes and solvents interact.”
To learn more about the Schwartz group’s research, visit their website.
From DOE Science News Source:
Chemicals Can Change Their Identity, Thanks to the Liquids Where They Reside
Far from being a mere spectator, solvents can play a larger role in chemical reactions, likely including those used in energy storage and biology.
A “snapshot” reveals that the surrounding tetrahydrofuran solvent deforms the bonding electron density around a sodium solute. The sodium cores are blue spheres; the valence electrons’ density is represented as a transparent white surface with a white wire mesh enclosing most of the charge density. The bonds between sodium and nearby solvent’s oxygen sites are thin yellow lines. Image courtesy of Devon Widmer, UCLA.
Toss a few whole almonds in a jar full of hazelnuts. Shake. The nuts bounce against each other, but they don’t react. That’s how some people think of reactions happening inside liquids. The solutes (almonds) react with each other in a sea of solvent (hazelnuts). But a new study shows that this is not always the case for real chemical reactions. Under the right conditions, the solvent can change the chemical identity of the solute.
Many chemical reactions, particularly those relevant to keeping people and plants alive, happen in solution.This research shows that in many such reactions, the solvent is not a mere spectator. That means retooling expectations and computational models. Because the same rules could apply in chemistry labs, researchers may need to select their solvents with more care. The solvents could be controlling or changing the chemical identity of the solute.
Although solvents are carefully selected in some cases, the liquids are often simply considered a medium to allow the reactants to encounter each other. However, the solvent may play a larger role. Here, researchers found that when the solvent and solute interact (energetically on the same order as a hydrogen bond), the solvent can control the bond dynamics and the chemical identity of simple solutes. The researchers came to this conclusion studying a sodium dimer in the weakly polar solvent tetrahydrofuran. Bonding interactions between the solvent and sodium atoms led to unique coordination states. These states had to cross a free energy barrier, essentially undergoing a chemical reaction, to interconvert. Further, each coordination state had its own dynamics and spectroscopic signatures. Although chemists have long been aware of the influence of solvents in certain cases, this research highlights the value of carefully selecting the solvent to create a specific environment in certain condensed-phase chemical systems.
Devon R. Widmer
University of California, Los Angeles
Benjamin J. Schwartz
University of California, Los Angeles
Early portions of this work were supported by the National Science Foundation. Beginning in September 2017, this work was supported by the Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. The researchers used the Hoffman2 Computing Cluster at the Institute for Digital Research and Education at the University of California, Los Angeles.
D.R. Widmer and B.J. Schwartz, “Solvents can control solute molecular identity.” Nature Chemistry 10, 910 (2018). [DOI: 10.1038/s41557-018-0066-z]
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Nature Chemistry article: Behind the Paper: How Solvents Can Control Solute Molecular Identity
The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
Penny Jennings, UCLA Department of Chemistry & Biochemistry, email@example.com.