Shape-Shifting Molecules

Some organic molecules are capable of undergoing tautomerism. In tautomerism, the atoms in a molecule are rearranged to form another molecule with the same formula but with different connections between atoms. These two structures are called tautomeric forms. With certain molecules the conversion between tautomeric forms can be very quick: the molecule can shape shift back and forth many times a second.

tautomers

Recently, we were able to take advantage of this property to make an unusual reaction happen. The red bonds between carbon and hydrogen in structure 1 are normally very hard to break. By switching to the tautomeric structure 2, one of these bonds, shown in blue, becomes much easier to break. We replaced this hydrogen atom with deuterium, an isotope of hydrogen with similar chemical properties, to prove this. Replacing hydrogen atoms in a molecule for deuterium is an important chemical process, but it usually requires catalysts (metal complexes which speed up reactions), high temperatures, or strong acids or bases. Instead, we discovered that we can easily swap hydrogen and deuterium atoms by taking advantage of tautomerization.

This work was done primarily by Hessam, a PhD student in our group, with help from Francesco Lelj who did the calculations.

http://pubs.acs.org/doi/abs/10.1021/acs.joc.5b00539

-Hessam and Debbie

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