Replacement of fluorine

Many reactions of fluorinated organics with metal halides result in the replacement of fluorine with halogen A general route to 1,1,1-trichloro- or tribromo-fluoroalkanes involves treating primary fluoroalkyl iodides with aluminum trichloride or aluminum tribromide [74], Benzylic [75, 76] or vinylic [72] fluorine can be exchanged for chlorine when treated with aluminum trichloride... 

Vinyl and phenyl mfluoromethyl groups are reactive in the presence of aluminum chloride [10] Replacement of fluorine by chlorine often occurs Polyfluori-nated trifluoromethylbenzenes form reactive a,a-difluorobenzyl cations in antimony pentafluoride [11] 1 Phenylperfluoropropene cyclizes in aluminum chloride to afford 1,1,3-trichloro 2 fluoroindene [10] (equation 10) The reaction IS hypothesized to proceed via an allylic carbocation, whose fluoride atoms undergo halogen exchange... 

The partially reduced form of niobium accounts for the color change of samples that underwent thermal treatment in vacuum or inert atmospheres. Whereas the thermal treatment of the mixture in air leads to the simultaneous oxidation of Nb4+ by oxygen, this is actually equivalent to the replacement of fluorine ions by oxygen ions in the complex structure of oxyfluoroniobate. Extended thermal treatment of systems containing LiNbOF4 and LiF yields a mixture of LiF and LiNbOs as the final thermal decomposition product. 

The stepwise replacement of fluorine atoms in fluorocyclophosphazenes, (NPF2) n = 3—5), by methyl groups has been followed.and n.m.r. spectroscopy showed that methyl-lithium in diethyl ether generally effects a geminal replacement pattern. With N3P3F6, only mono- and di-methyl derivatives were obtained, but with N4P4F8 the dimethyl (52), trimethyl (53), and octamethyl derivatives were noted. The formation of... 

In anaerobic microcosms, l,l,2-trichloro-l,2,2-trifiuoroethane (CFC-113) was transformed by successive reductive dechlorination to l,2-dichloro-l,2,2-trifiuoroethane (HCFC-123a), and under methanogenic conditions to l-chloro-l,2,2-trifiuoroethane (HCFC-133) and l-chloro-l,l,2-triflnoroethane (HCFC-133b) without evidence for the reductive replacement of fluorine (Fignre 7.70b) (Lesage et al. 1992). 

Replacement of fluorine by a halogen atom of a higher period will result into greater a—it stabilization of the gauche relative to the cis conformer. 

As the structurally modified version of LiPFe, LiFAP has also been reported to be less chemically sensitive due to the partial replacement of fluorine with the more stable perfluorinated alkyls. Aurbach and co-workers investigated the stability of... 

Replacement of Fluorine by Alkoxy and Aryloxy Groups 4.2.1. In Aliphatic Compounds... 

Examples of replacement of fluorine in saturated aliphatic perfluorinated compounds by alkoxy and aryloxy groups are relatively scarce since such fluorine atoms are generally inert toward nucleophiles in SN2 reactions. 

Replacement of fluorine occurs when l,l,l-trifluoro-2,2-dihaloethanes 1 are treated with alkaline alkoxides.59 The products, alkyl 1,1 -difluoro-2,2-dihaloethyl ethers, are probably formed by two separate reactions these are elimination of hydrogen fluoride to give an alkene, followed by addition of the alcohol.59... 

Replacement of fluorine by alkoxy groups also takes place in fluorinated bicyclic alkenes. Hexafluorobicyclo[2.2.0]hexa-2,5-diene (32) when treated with sodium ethoxide in ethanol gives two diethoxy-substituted products.79... 

Evidently, hydrogen facilitates the nucleophilic replacement of fluorine by the methoxy group more efficiently than the halogens fluorine < chlorine < bromine < iodine < hydrogen.83,84 1,2,4,5-Tetrafluorobenzene when treated with sodium methoxide in methanol yields 1,2,4-tri-fluoro-5-methoxybenzene (7).83... 

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