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Concept
Organofluorine chemistry
Résumé
Organofluorine chemistry describes the chemistry of organofluorine compounds, organic compounds that contain a carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, refrigerants, and reagents in catalysis. In addition to these applications, some organofluorine compounds are pollutants because of their contributions to ozone depletion, global warming, bioaccumulation, and toxicity. The area of organofluorine chemistry often requires special techniques associated with the handling of fluorinating agents.
Carbon-fluorine bond
Fluorine has several distinctive differences from all other substituents encountered in organic molecules. As a result, the physical and chemical properties of organofluorines can be distinctive in comparison to other organohalogens.
The carbon–fluorine bond is one of the strongest in organic chemistry (an average bond energy around 480 kJ/mol). This is significantly stronger than the bonds of carbon with other halogens (an average bond energy of e.g. C-Cl bond is around 320 kJ/mol) and is one of the reasons why fluoroorganic compounds have high thermal and chemical stability.
The carbon–fluorine bond is relatively short (around 1.4 Å).
The Van der Waals radius of the fluorine substituent is only 1.47 Å, which is shorter than in any other substituent and is close to that of hydrogen (1.2 Å). This, together with the short bond length, is the reason why there is no steric strain in polyfluorinated compounds. This is another reason for their high thermal stability. In addition, the fluorine substituents in polyfluorinated compounds efficiently shield the carbon skeleton from possible attacking reagents. This is another reason for the high chemical stability of polyfluorinated compounds.
Fluorine has the highest electronegativity of all elements: 3.98. This causes the high dipole moment of C-F bond (1.41 D).
Fluorine has the lowest polarizability of all atoms: 0.56 10−24 cm3.
Source officielle
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