Fluorocarbons

An elusive ion caught sticking around

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Science  10 Oct 2014:
Vol. 346, Issue 6206, pp. 205-206
DOI: 10.1126/science.346.6206.205-f

Trifluoromethyl groups are found in a wide variety of compounds, including such well-known drugs as Prozac and Celebrex. Chemists often incorporate them into molecules through methods that might seem to involve the intermediacy of the negatively charged CF3 anion. However, this intermediate has stayed out of sight in solution, leaving its stability in doubt. Prakash et al. now have succeeded in catching it on camera, so to speak (actually in nuclear magnetic resonance spectra). To make it, they treated CF3H and several silyl-substituted analogs with potassium t-butoxide base, and then bound the potassium counterion in a crown ether. The anion persisted for days in tetrahydrofuran solvent at minus 78°C.

Angew. Chem. Int. Ed. 53, 10.1002/anie.201406505 (2014).

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