Halogen monofluoride

Halogen monofluorides are generated by the reaction of halogens with fluorine gas diluted with nitrogen. They are strongly electrophilic becasue of their attachment to the most... 

Mixtures of halogen and halogen polyfluorides are effective sources of the corresponding halogen monofluorides in reactions with fluoroolefins.—E Deca-fluorocyclohexene shaken 26 hrs. at 265° with bromine trifluoride and bromine in an autoclave bromoundecafluorocyclohexane. Y 78%. F. e., also with iodine pentafluoride/iodine, s. R. D. Ghambers, W. K. R. Musgrave, and J. Savory, Soc. 1961, 3779. 

Ha.logen Fluorides. These include compounds such as IF, IF, GIF, etc, of which only a few, GIF, GIF, BrP, and IF, are used to some extent. They act both as halogen exchange agents and, in the case of the monofluorides, as addition agents to unsaturated bonds (17). 

The effect of the substituent group can be seen in the reactions of the following senes of halogenated esters Methyl 2,3 dichloro-3-fluoro-2-methylpropionate and chlorine monofluoride first form methyl 2-chloro-3,3-difluoro-2-methylpro-pionate An additional equivalent of chlorine monofluoride produces methyl 2 methyl-2,3,3-trifluoropropionate (equation 14)... 

The stoichiometric equivalents of halogen fluorides, i.e. chlorine monofluoride, bromine monofluoride and iodine monofluoride, have found a wide application in addition reactions to double bonds. The equivalents are obtained by reacting A -haloamides or free halogens in combination with hydrogen fluoride or its salts as the source of fluoride ions. The reactions proceed under mild conditions at — 80 to 20 "C in anhydrous hydrofluoric acid or diethyl ether, tetrahydro-furan, dichloromethane or chloroform mainly by electrophilic addition with Markovnikov-type regioselectivity (anti addition).26-28... 

The addition of halogen fluorides to C = C bonds in steroids is affected by steric crowding to a greater extent than by electronic factors so that the products may be of the anti-Mar-kovnikov type. In several instances the orientation of the bromine monofluoride addition was shown to depend on reaction conditions resulting cither in 6/ -bromo-5a-fluoro- or 5a-bromo-6/i-fluorosteroids.33... 

The triatomic cations are usually prepared from the corresponding interhalogen, by reaction with a halogen acceptor molecule. This is impossible for some of the more exotic species which have no interhalogen precursor. For example, the [Br3]+ cation has been characterized20 in [Br3]+[AsF6], formed from the interaction of arsenic pentafluoride and a bromine/bromine pentafluoride mixture and the [Cl FJ cation results from the interaction of antimony pentafluoride with chlorine monofluoride.21... 

When BrF3 is mixed with bromine, the active species is bromine monofluoride and this can be added to olefins (equation 118)213. Bromine trifluoride also used to prepare compounds with hypervalent heteroatoms, many of them, unattainable otherwise (equation 119)214. A key step in Lemal and coworkers unique synthesis of perfluorocyclopentadiene involved also an oxidative fluorination (equation 120)215. BrF3 can also substitute halogens and was used for the preparation of L-3-fluoroalanine 21 (equation 121)216. 

The diatomic compounds are C1F, BrF, BrCl, IBr, and IC1. In their physical properties they are usually intermediate between the constituent halogens. They are of course polar, whereas the halogen molecules are not. Chlorine monofluoride... 

A good method for the chlorofluorination of halogenated alkenes is the use of hexachloro-melaminc and anhydrous hydrogen fluoride. Chlorofluoroalkanes can be prepared in yields of 25 to 70 % (see Table 18). Other reagents for chlorofluorinations are chlorine monofluoride, chlorine Irifluoride or the sulfur tetrafluoride/hydrogen fluoride/chlorinc system (see Table 18). 

Chlorofluorination of Halogenated Alkenes with Chlorine Monofluoride in Chloroform General Procedure ... 

If the constant electron transfer feature is real, we would expect to find similar effects in electronically related nonnoble gas compounds. Consider, for example, the formation of the halogen fluorides. The centr atom of the monofluorides can be thought of as a pseudo-rare-gas atom and the subsequent formation of the trifluorides and pentafluorides via a three-center bonding scheme is analogous to the formation of rare gas difluorides and tetrafluorides. If the constant electron transfer is due to independence of the perpendicular, three-center bonds, we could expect the two equivalent fluorines in BrFs each to have the same charge as each of the four equivalent fluorines in BrFs. The X-ray photoelectron spectra of these molecules have been measured in this laboratory and are currently being analyzed. Finally, it is known that the thermo-... 

Tertiary alkyl halides are easier to reduce than secondary alkyl halides, which are, in turn, easier to reduce than primary alkyl halides. Ease of reduction of a carbon-halogen bond is governed by the identity of the halogen atom (a) iodides are easier to reduce than bromides, (b) chlorides are so difficult to reduce that they often appear to undergo no direct reduction, and (c) no report of the direct reduction of an alkyl monofluoride has been published. Finally, the existence of the radical anion [RX ], formed by addition of one electron to an alkyl monohalide, has never been demonstrated Andrieux and coworkers [8] have discussed why such a species is not expected for simple alkyl monohalides, but why radical anions of aromatic halides are distinct intermediates in the electrochemical reduction of aromatic halides. Canadell and coworkers [9] have described the implications of theoretical calculations pertaining to the lifetime of the water-solvated radical anion of methyl chloride. 

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