Magnesium-fluorine bonds

The range of possible fluorination reactions on electron-rich double bonds, eno-lates, and enol ethers, with Selectfluor (F-TEDA-BF4) as example, is depicted in Scheme 2.88. Yields from the fluorination of unstabilized carbanions, for example phenyl magnesium bromide, are usually relatively low, mostly because of competing oxidation side-reactions. 

SAMPLE SOLUTION (a) Of the two halogen substituents on the aromatic ring, bromine reacts much faster than fluorine with magnesium. Therefore, fluorine is left Intact on the ring, while the carbon-bromine bond is converted to a carbon-magnesium bond. 

Magnesium reacts with fluorine to form magnesium fluoride. Write an equation to describe the bonding using Lewis symbols. 

Generally, PTFE is not susceptible to nucleophilic attack because of the absence of double bonds. It is still suseeptible to loss of fluorine by electrophilic attack particularly under heat and over long periods of exposure. Alkali metals, which are highly reactive elements, sueh as eesium, potassium, sodium, and lithium, are among the most likely candidates for abstraction of fluorine from PTFE by an eleetrophilic mechanism. Certain other metals such as magnesium can attack PTFE if they are highly activated hy etching or other means. 

---