Use of Fluorocarbons to Carry Oxygen

Halons (vide supra) and related compounds provide evidence that the presence of halogen reduces the ease of combustion. It is held that radical-chain inhibition by halogen atoms may play a role. Since the presence of halogens inhibits oxidation. 

It is possible to consider that elimination of hydrogen halide (H-X X = F, Cl, Br, I) from an alkyl or alkenyl halide constitutes oxidation as the alkene (or alkyne) that results contains less one proton less (i.e., oxidation corresponding to the loss of hydrogen). However, while alkenes (or alkynes) are doubtlessly in a higher oxidation state than the corresponding alkanes (to which they can be reduced) they are, nonetheless, in the same oxidation state as the alkyl halide from which they were produced—as measured by electron loss and gain (Introduction to Part II). 

Although particularly sensitive to subtle structural and electronic effects, it is found that some primary alkyl halides (RCHjX X = Cl, Br, I) will react with meth-ylsulfinylmethane (dimethyl sulfoxide [DMSO] [(CH3)2SO]) in the presence of a weak base such as sodium carbonate (Na2C03) or sodium hydrogen carbonate (sodium bicarbonate, NaHCOs) to produce the corresponding aldehyde. 

Before leaving the topic of oxidation of alkyl halides, it is worthwhile noting that benzylic (C6H5CH2X X = Cl, Br, I) and allylic (RCH=CH-CH2X X = Cl, Br, I) halides and related compounds that form stabilized carbocations, have long been known to undergo oxidation by heating them with hexamethylenetetramine (l,2,5,8-tetraazatricyclo[3.3.1.1 ]decane) in water.  

While aryl halides are particularly resistant to oxidative destruction, alkenes, in which there is at least one halogen on one of the carbons of the double bond, that is, vinylic (Equation 7.7), undergo oxidation with a variety of oxidants (e.g., potassium permanganate, KMn04) in aqueous solution to produce the corresponding carboxylic acids (presumably via the acid halide). 

---