Bromine Chloride


[13863-41-7]  · BrCl  · Bromine Chloride  · (MW 115.36)

(powerful brominating and/or bromochlorinating agent)

Physical Data: mp ca. -66 °C; bp ca. 5 °C.1

Solubility: sol H2O, methylene chloride, chloroform, carbon tetrachloride, carbon disulfide, ether.

Form Supplied in: while bromine chloride (occasionally referred to incorrectly as chlorine bromide) is commercially available, it is more commonly prepared in the laboratory on demand.

Preparative Methods: these include the reaction of Br2 and Cl2 in solution;2,3 reaction of HCl gas with either N-bromoacetamide (NBA)4 or N-bromosuccinimide (NBS)5 in halogenated solvents; reaction of NaBr with either Cl26,7 or chloramine-T7 in aqueous solution. Appropriate literature reference(s) should be consulted for particular applications.

Handling, Storage, and Precautions: as a source of positive halogen, all precautions associated with the use of halogens (see Bromine, Chlorine) should be observed. Protective clothing is a must, and in the case of gaseous BrCl (or preparations using corrosive gaseous reagents) the use of a respirator is advised. Use in a fume hood.

Bromination of Sulfones.

Bromine chloride has been used successfully in the photochemical bromination of sulfones. With 1 equiv of BrCl, tetrahydrothiophene 1,1-dioxide gave a 72% yield of the 2-bromo isomer, while diethyl sulfone gave a mixture due to a- and b-bromination.2 Attempts to effect bromination using other conditions (Bromine, Br2/Lewis acid, NaOBr, N-Bromosuccinimide, dioxane dibromide) were unsuccessful. Thietane 1,1-dioxide (1) has been brominated in the 3-position (eq 1),3,8 but the product was reported to be contaminated with some of the 3-chloro compound.9

Bromination of Aromatic Rings.

Bromine chloride has been used as an alternative to Br2 in the electrophilic bromination of aromatic rings.6 In this case, chlorine was not incorporated onto the ring.

Addition to Alkenes.

The addition of BrCl to alkenes is governed by a combination of steric and stereoelectronic effects.5,10,11 Thus while (2) reacts with BrCl to give a mixture of isomers (eq 2), the sterically more demanding (3) gives a single compound (eq 3).5a Steroids, with their highly rigid framework, also demonstrate excellent regio- and stereoselectivity (eqs 4 and 5).4,5

Bromination of Organoboranes Under Ionic Conditions.

When organoboranes are treated in the dark with BrCl (or Br2) in the presence of H2O, good yields of alkyl bromides are obtained.7 This method works best for the synthesis of primary bromides from terminal alkenes (eq 6). In this sense it complements the radical bromination of organoboranes, which has been shown to prefer secondary alkyl groups.

Related Reagents.

Bromine; N-Bromoacetamide; N-Bromosuccinimide; Chloramine-T; Chlorine; N-Chlorosuccinimide; Sodium Bromide.

1. CRC Handbook of Chemistry and Physics, 74th ed.; Lide, D. R., Ed.; CRC Press: Boca Raton, FL, 1993; p 4-45.
2. Dronov, V. I.; Snegotskaya, V. A. JOU 1970, 6, 2038.
3. Dittmer, D. C.; Nelsen, T. R. JOC 1976, 41, 3044.
4. Ziegler, J. B.; Shabica, A. C. JACS 1952, 74, 4891.
5. (a) Hageman, H. J.; Havinga, E. RTC 1966, 85, 1141. (b) Bellucci, G.; Ingrosso, G.; Marioni, F.; Mastrorilli, E.; Morelli, I. JOC 1974, 39, 2562.
6. Obenland, C. O. J. Chem. Educ. 1964, 41, 566.
7. Kabalka, G. W.; Sastry, K. A. R.; Hsu, H. C.; Hylarides, M. D. JOC 1981, 46, 3113.
8. Lancaster, M.; Smith, D. J. H. S, 1982, 582.
9. Sedergran, T. C.; Yokoyama, M.; Dittmer, D. C. JOC 1984, 49, 2408.
10. (a) de la Mare, P. B. D.; Galandauer, S. JCS 1958, 36. (b) Negoro, T.; Ikeda, Y. BCJ 1986, 59, 2547.
11. Deslongchamps, P. Stereoelectronic Effects in Organic Chemistry; Pergamon: Oxford, 1983.

R. Richard Goehring

Scios Nova, Baltimore, MD, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.