Addition of molecular fluorine

The analysis of the syn-addition of molecular fluorine to ethylene at the MP2/6-31 +G level with IRC calculations indicates that F2 approaches the C=C bond vertically at the middle to form a perpendicular complex 38 as the intermediate. The latter complex then re-orientates to a rhombic-type transition state 39 to give the final syn-addition product 4084. This analysis rules out the involvement of the square-type complex 41 proposed earlier. However, these calculations do not clarify the F2 addition to electron-deficient alkenes, such as acrylonitrile84. 

The addition of molecular fluorine to phenylacetylenes in trichlorofluoromethane as solvent yields the corresponding tetrafluorides as the main product, e.g. 2, while the use of methanolic solutions leads to the formation of rem-fluoro ethers 3 and dimethyl ketals 4 as well as tetrafluorides 2. ... 

The transition state structure for the addition of molecular fluorine to ethylene VIIc was found by the 3-2IG calculations [17] to closely resemble that for the addition of HCl (IV). Of special interest are the computational results obtained on transition state structures Vlld, Vile for gas phase electrophilic addition reactions of molecular chlorine and bromine to ethylene. Whereas the four-centered structure VIIc for the fluorination of ethylene indicates concerted c/s-addition, which is in accord with experimental finding for this reaction [18], the transition state geometries for chlorination and bromination may be regarded as cyclic halonium ions backed by halogenide counter-ions. Noteworthy is that the calculations [17] predict the heterolysis to occur intrinsically without any assistance from polar solvents. The three-centered structures Vlld, Vile help to clarify the reason for trans-stereoselectivity of the chlorination and bromination reactions of ethylene [1, 19]. 

In other work Rozen added molecular fluorine to a steroidal ene-one dissolved in ethanol at low temperatures to produce a vicinal difluonde in a cleaner, better yield reaction than previously obtainable [55] Although the reaction was not general, the stereoselectivity was very high, and contrary to addition of other halogens, addition was r>ii, characteristic of an electrophilic addition pathway... 

Oxidation of 44 is completely inhibited by the addition of a small amount of 2,4,6-tri-f-butylphenol. Consequently, the oxidation of the Si—Si bond with oxygen displays the following features 1) a Si—Si bond which is either angle-strained or substituted with more than two fluorine atoms is easily oxidized 2) a radical mechanism is operative 3) the insertion of oxygen into the Si—Si bond proceeds stereospecifically . Incorporation of molecular oxygen was also observed in the direct photolysis of the cyclopolysilanes 80 and 81 (equations 88 and 89) . ... 

Light-induced transformations over fluorinated titania (TiOi/F) cannot be initiated either by =Ti— 0 (OHads), due to the lack of =Ti—OH groups, or by SET from a surface complexed substrate, due to the fluoride competition. In addition to these major effects, the adsorption of molecular oxygen can be affected also and the surface charge is dramatically decreased. The last effect may be important particularly for charged substrates and intermediates and for the possibility of interfacial electron transfer. 

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