Bromine trifluoride

In this and the next section, we consider two aprotic non-aqueous solvents. 

The cyclic periodate ester breaks down spontaneously, as shown below, creating a pair of carbonyl groups and a pentavalent, pentacoordinate iodine intermediate  

The iodine intermediate, which may be viewed as a hydrated form of iodic acid, should then eliminate water to yield iodate (103 ). A water-catalyzed pathway is shown below  

Diol cleavage played an important role in natural product structure analysis in the days before instrumental analysis. Understandably, the importance of periodic acid oxidations has diminished somewhat in modern organic chemistry. 

Bromine trifluoride is very useful for creating CF2 and CF3 groups, which are present in a variety of drugs, anesthetics, and other biomedical products. Thus, carboxylic acids can be converted to CF3 compounds with Brp3, albeit after initial conversion to the xanthate esters, as shown below  

A few quick comments on the first three steps of the transformation may be useful SOCI2 converts the COOH to COCl, RSH then converts COCl to C(0)SR (thioester), and Lawesson s reagent (which we discussed in Section 6.14) then converts the thioester to the xanthate. As soft nucleophiles, the sulfurs in the xanthate attack the Br in BrFj, a soft electrophile. Simultaneously, or in the next step, a fluoride migrates from Br to the xanthate carbon. Migration of a second fluoride leads to a CF2 unit, as shown below  

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The concept of acids and bases has been extended to solvents which are ionized and yet do not contain hydrogen a substance giving the appropriate positive ion is an acid on that system. Thus bromine trifluoride ionizes... 

For ionized solvents which do not contain protons a base is a substance which reacts with the acid of that system to give a salt and the solvent. Thus the base KBrp4 reacts with the acid BrFiSbFfi to give the salt KSbF and Brp3 in bromine trifluoride. 

It is dissolved by bromine trifluoride, to form finally gold(III) fluoride, AuFj. This is a notable compound, for in it gold exhibits a simple valency of three, whereas in all other gold(III) compounds, gold is 4-coordinate, usually by complex formation (see below). 

Fluorine reacts with the halogens and antimony to produce several compounds of commercial importance antimony pentafluoride [7783-70-2J, bromine trifluoride [7787-71 chlorine trifluoride [7790-91 -2J, and iodine pentafluoride [7783-66-6J. Chlorine trifluoride is used in the processing of UF (see Uraniumand uranium compounds). Bromine trifluoride is used in chemical cutting by the oil well industry (see Petroleum). Antimony and iodine pentafluorides are used as selective fluorinating agents to produce fluorochemical intermediates (see Fluorine compounds, inorganic). 

The halogen fluorides are binary compounds of bromine, chlorine, and iodine with fluorine. Of the eight known compounds, only bromine trifluoride, chlorine trifluoride, and iodine pentafluoride have been of commercial importance. Properties and appHcations have been reviewed (1 7) as have the reactions with organic compounds (8). Reviews covering the methods of preparation, properties, and analytical chemistry of the halogen fluorides are also available (9). 

Bromine Trifluoride. Bromine trifluoride is a colorless Hquid. The commercial grade is usually amber to red because of slight bromine contamination. The molecule has a distorted T stmeture (26). Infrared spectral data (26—30), the uv-absorption spectmm (31), and vapor pressure data (32) may be found in the Hterature. 

Liquid Halogen Fluorides as Reaction Media. Bromine trifluoride and iodine pentafluoride are highly dimerized and behave as ionizing... 

Bromine Trifluoride. Bromine trifluoride is produced commercially by the reaction of fluorine with bromine ia a continuous gas-phase process where the ratio of fluorine to bromine is maintained close to 3 1. It is also produced ia a Hquid-phase batch reaction where fluorine is added to Hquid bromine at a temperature below the boiling poiat of bromine trifluoride. 

U.S. production of bromine trifluoride is several metric tons per year mostiy used in oil-weU cutting tools. Air Products and Chemicals, Inc. is the only U.S. producer. The 1992 price was ca 80/kg. 

J. W. Grisard and G. D. Oliver, The Hapor Pressure and Heat Hapori ation of Bromine Trifluoride, R-25, Plant Report R-766, U.C.C. Nuclear Co., Oak Ridge, Term., June 8, 1951. 

Silver Tetrafluoroborate. Silver tetrafluoroborate [14104-20-2], AgBF, is formed from silver borate and sodium borofluoride or bromine trifluoride. It is soluble in organic solvents. 

Thallium (ITT) fluoride has been prepared by the action of fluorine or bromine trifluoride on thaUium(III) oxide at 300°C. It is stable to ca 500°C but is extremely sensitive to moisture. Thallium (ITT) chloride can be obtained readily as the tetrahydrate [13453-33-3] by passing chlorine through a boiling suspension of HCl in water. It can be dehydrated with thionyl chloride. Thallium (ITT) bromide tetrahydrate [13453-29-7] is prepared similarly, whereas the iodide prepared in this manner is thaUium(I) triiodide [13453-37-7] H" F2-... 

Bismuth pentafluoride is an active fluorinating agent. It reacts explosively with water to form ozone, oxygen difluoride, and a voluminous chocolate-brown precipitate, possibly a hydrated bismuth(V) oxyfluoride. A similar brown precipitate is observed when the white soHd compound bismuth oxytrifluoride [66172-91 -6] BiOF, is hydrolyzed. Upon standing, the chocolate-brown precipitate slowly undergoes reduction to yield a white bismuth(Ill) compound. At room temperature BiF reacts vigorously with iodine or sulfur above 50°C it converts paraffin oil to fluorocarbons at 150°C it fluorinates uranium tetrafluoride to uranium pentafluoride and at 180°C it converts Br2 to bromine trifluoride, BrF, and bromine pentafluoride, BrF, and chlorine to chlorine fluoride, GIF. It apparently does not react with dry oxygen. 

Bromine monofluoride [13863-59-7], BrF, can be prepared by the direct reaction of Br2 and F2, but because it readily disproportionates it has never been prepared in pure form (57). However, BrF can be prepared in situ by the reaction of Br2 with AgF in benzene (58) or by the reaction of A/-bromoacetamide and HF in ether (59). BrF adds to simple alkenes at room temperature to give products of trans-addition. Bromine trifluoride [7787-71-5], BrF, can be formed from gaseous fluorine and Hquid bromine (60). Bromine pentafluoride [7789-30-2], BrF, is formed from the reaction of BrF vapor with gaseous fluorine at 200°C (60). The tri- and pentafluorides are commercially available. As strong fluorinating agents they are useful in... 

The time-weighted, 8-h average limit for exposure to bromine pentafluoride is 0.1 ppm (67). Materials of constmction suitable for use with the bromine fluorides include nickel. Monel metal, or Teflon. For shipping, bromine trifluoride and pentafluoride are classified as oxidizers under DOT regulations. The trifluoride also requires a poison label. 

Bromine trifluoride and pentafluoride Chlorine trifluoride Iodine monochloride... 

Fluorine has also been added successfully to perfluorinated aromatic compounds, as illustrated in equation 6 [57, 58, 59, 60, 61], Also bromine trifluoride adds fluorine to pentafluorophenol [56] and octatluoronaphthalene [62]... 

Reactions of the halogen iluorides with other unsaturated functional groups are generally reported only with highly fluorinated substrates Hexafluorobenzene and denvatives [118] and octaflvoronaphthalene [119] react with mixtures of bromine and bromine trifluoride by 1,4 addition of fluorine followed by addition of bromine fluoride across a reniatning double bond (equation 22)... 

Conversion of 2-chloro-2-difluoromethoxy-l,lJ trifluoroethane to 2-difluo-romethoxy-l,l,l,2-tetrafluoroethane (98% purity) is accomplished with bromine trifluoride. The starting material is the major impurity [7] (equation 4)... 

Table 1. Effect of Solvent on Displacement of Halogen to 40% Conversion by Bromine Trifluoride [10]...

On the other hand, oxidizing fluonnating agents like silver difluoride, xenon difluoride, or bromine trifluoride replace one chlorine group and then cleave the sulfur-nitrogen bond [56],... 

Bromine trifluoride, though it reacts explosively with water and hydrocarbon tap greases, is somewhat less violent and vigorous a fluorinat-ing agent than is CIF3. The sequence of reactivity usually quoted for the halogen fluorides is ... 

Another anhydrous solvent that is frequently used for the synthesis of tantalum and niobium fluoride compounds is bromine trifluoride, BrF3. At ambient temperature, bromine trifluoride is light yellow liquid characterized by a boiling point of 126°C, a melting point of 9°C and a density of 2.84 g/cm3 at melting temperature. 

In its liquid form, bromine trifluoride dissociates according to Equation (6) ... 

These four solvents can thus be termed protogenic solvents, whilst bromine trifluoride and sulphur dioxide which do not contain hydrogen are non-protonic solvents. Non-ionising solvents include hydrocarbons, ethers, esters and higher alcohols the lower alcohols, especially methanol and ethanol, do show slight ionising properties with appropriate solutes. 

Pt is attacked by bromine trifluoride at 280° in the presence of K fluoride (Ref 5). Finely divided Pt and some other metals will cause a mixt of Hj and 02 to explu at ordinary temps (Ref 1). A little Pt black dropped into a hydrogen peroxide soln can cause an expln (Ref 2). Pt and molten Ii react violently at 540° 20° (Ref 7), and an incandescent reaction occurs when it is wanned gently in gaseous oxygen difluoride (Ref 6). The decompn of 92% per-monosulfuric acid is expl in the presence of smooth or finely divided Pt (Ref 3). The re-. acting mass formed by the mixt of P and Pt can become incandescent when heated (Ref 8). Dry, used Pt catalyst has exWd while being screened (Ref 4)... 

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