Carbon-fluorine bond-breaking macrocycle
after reaction with methyl fluoride (CH3F)
At sea level, the strong C-F bond makes fluorocarbons thermally and chemically stable. As a result, fluorocarbons have been used in many commercial applications including refrigerants, pesticides and non-stick coatings. In the upper atmosphere, however, high-energy photons and highly reactive ozone molecules can break apart fluorocarbons, with the consequence of a depleted ozone layer and increased ultraviolet radiation.
Fluorocarbons can be broken down at ground level with certain organometallic compounds, but the reactions take a long time at very high temperatures. Other known reagents are both highly toxic and inefficient, so chemists have been searching for an economical and environmentally friendly method to dispose of fluorocarbons.
Reasoning that the problem already may have been solved by nature, a team from the National Institute of Standards and Technology (NIST) and the Interdisciplinary Network of Emerging Science and Technology group (INEST) looked to an enzyme called fluoroacetate dehalogenase used by a South African bacterium, Burkholderia sp. The enzyme enables the bacterium to pull the fluoride ion out of sodium fluoroacetate at room temperature and without problematic metal ions.
Enzymes can be difficult and expensive to adapt to an industrial process. Instead, the research team applied basic quantum mechanical theory of electron structures in molecules, together with the example of a known molecule that binds to and extracts chlorine ions, to calculate the make-up and geometry of the critical "active site" in the enzyme that does the work. They then designed in software a large ring-shaped molecule to hold those components in just the right orientation to break the C-F bond in methyl fluoride, a simple fluorocarbon.
Researchers at the University of Texas now are synthesizing the new molecule to test its effectiveness. If it matches theoretical predictions, it will be the first example of a simple organic molecular system able to break C-F bonds without extreme temperature and pressure conditions.
COMPAMED.de; Source: National Institute of Standards and Technology (NIST)