POTASSIUM BROMATE 1
Potassium Bromate Other deactivated aromatics that can be brominated by this
method include benzoic acid,2,14 halobenzoic acids,15 phthalic
acid,2 hydroxybenzoic acid,16 halobenzenes,15,17 benzonitrile,16
KBrO3
benzanilide,16 cinnamic and hydrocinnamic acids,16 phenylacetic
acid,16 benzophenone,16 acetophenone,2 and 2,5-dimethyl-1,3,
[7758-01-2] BrKO3 (MW 167.00)
4-oxadiazoles.18 In the case of acetophenone, the bromination
InChI = 1/BrHO3.K/c2-1(3)4;/h(H,2,3,4);/q;+1/p-1/fBrO3.K/q-
occured at the aromatic ring and not on the methyl group,19 which
1;m
is the normal position for attack using molecular bromine (eq 3).
InChIKey = OCATYIAKPYKMPG-RERGACQYCO
KBrO3
+ (3)
(convenient source of molecular bromine;1a used for bromination
50% H2SO4
Br
of deactivated aromatics;2 used in chemical oscillating reactions3)
rt
OO Br O
ć% ć%
Physical Data: mp H"350 C, dec H"370 C with evolution of oxy- 60% 10%
gen; d 3.27 g mL-1.
One report in which sodium bromate is used in combination
Solubility: sol 12.5 parts water, 2 parts boiling water; almost insol
with Bromotrimethylsilane for the bromination of aromatic rings
alcohol.
has appeared.20 While activated rings such as anisole and phe-
Form Supplied in: white crystals or granules; widely available.
ć%
nol react satisfactorily, deactivated rings do not. Toluene gave the
Drying: for analytical work dry at 100 110 Cfor 1h.
benzyl bromide product instead of the ring brominated product.20
Handling, Storage, and Precautions: potassium bromate is a
strong oxidizing agent (standard potential 1.44 V). Toxicity is
Chemical Oscillators. Chemical oscillating reactions such
low. Keep from contact with mineral acids and organic com-
as the Belousov Zhabotinski reaction3 and a clock reaction21
pounds during storage. Potassium bromate is an analytical stan-
have been reported using potassium bromate/sodium bromate.
dard for iodometry. Standard solutions are stable indefinitely.
Chemical oscillations such as these are driven by a combination
of bromination and oxidation reactions. A generalized mecha-
nism for bromate-driven oscillators controlled by bromide has
appeared.22 This is still an active area for investigation.23
Generation of Bromine and Bromination Reactions. Potas-
sium bromate and Sodium Bromate react with bromide ion in
dilute acid solution.1 to produce bromine according to eq 1.
1. (a) Diemente, D., J. Chem. Educ. 1991, 68, 932. (b) Jonnalagadda, S.
B.; Muthakia, G. K., J. Chem. Soc., Perkin Trans. 2 1987, 1539. (c)
BrO3 + 5 Br + 6 H+ 3 Br2 + 3 H2O (1)
Jonnalagadda, S. B.; Simoyi, R. H.; Muthakia, G. K., J. Chem. Soc.,
Perkin Trans. 2 1988, 1111.
As such, it is a convenient reagent for the bromination of 2. Harrison, J. J.; Pellegrini, J. P.; Selwitz, C. M., J. Org. Chem. 1981, 46,
2169.
alkenes, phenols, salicylic acid, aniline, and other activated
compounds.4 Synthetically useful brominations of methyl keto- 3. Franck, U. F., Angew. Chem., Int. Ed. Engl. 1978, 17, 1.
4. Day, A. R.; Taggart, W. T., Ind. Eng. Chem. 1928, 20, 545.
nes,5,6 3-substituted cyclohexenones,7 thiophene (in a two-phase
system),8 organoboranes (to produce an ą-bromoorganoborane 5. Winstein, S.; Jacobs, T. L.; Linden, G. B.; Seymour, D.; Levy, E. F.; Day,
B. F.; Robson, J. H.; Henderson, R. B.; Florsheim, W. H., J. Am. Chem.
which rearranges to the alcohol),9 cyclopentamethylenediphenyl-
Soc. 1946, 68, 1831.
stannane (to form cyclopentamethylenedibromostannane),10 and
6. Culbertson, T. P.; Domagala, J. M.; Peterson, P.; Bongers, S.; Nichols, J.
sulfonylhydrazides (to form sulfonyl bromides)11 have been
B., J. Heterocycl. Chem. 1987, 24, 1509.
reported.
7. Shepherd, R. G.; White, A. C., J. Chem. Soc., Perkin Trans. 1 1987,
2153.
Bromination of Deactivated Aromatics. Potassium bromate
8. Gol dfarb, Ya. L.; Dudinov, A. A.; Litvinov, V. P., Izv. Akad. Nauk SSSR,
in the absence of added bromide is an effective brominating agent.
Ser. Khim. 1982, 10, 2388.
An early report12 that potassium bromate in Sulfuric Acid, inthe
9. Brown, H. C.; Yamamoto, Y., Synthesis 1972, 699.
absence of added bromide, brominated benzene went unnoticed
10. Bajer, F. J.; Post, H. W., J. Org. Chem. 1962, 27, 1422.
for over 100 years. An efficient procedure for the bromination
11. Poshkus, A. C.; Herweh, J. E.; Magnotta, F. A., J. Org. Chem. 1963, 28,
of deactivated aromatic compounds has appeared.2 For example,
2766.
nitrobenzene2 has been brominated in 88% yield in this fashion
12. Krafft, F.; Merz, V., Chem. Ber. 1875, 8, 1045.
(eq 2). The reaction is dependent on the concentration of the sulfu-
13. (a) Gottardi, W., Monatsh. Chem. 1968, 99, 815. (b) Gottardi, W.,
ric acid. This method is arguably superior to other methods for ni-
Monatsh. Chem. 1969, 100, 42.
trobenzene bromination.13 (Warning! potassium bromate decom-
14. Banerjee, A.; Banerjee, S.; Samaddar, H., J. Indian Chem. Soc. 1979,
poses rapidly in 70% sulfuric acid solution with the evolution of
56, 985.
heat.2)
15. Banerjee, A.; Banerjee, G. C.; Dutt, S.; Banerjee, S.; Samaddar, H., J.
Indian Chem. Soc. 1980, 57, 640.
KBrO3
16. Banerjee, A.; Banerjee, G. C.; Adak, M. M.; Banerjee, S.; Samaddar, H.,
NO2 68% H2SO4 Br NO2
J. Indian Chem. Soc. 1981, 58, 985.
(2)
rt
17. Kosandal, K.; Bhujanga Rao, A. K. S.; Gundu Rao, C.; Singh, B. B.,
88%
Org. Prep. Proced. Int. Briefs 1991, 23, 395.
Avoid Skin Contact with All Reagents
2 POTASSIUM BROMATE
18. Blackhall, A.; Brydon, D. L.; Javaid, K.; Sagar, A. J. G.; Smith, D. M., 21. Rich, R. L.; Noyes, R. M., J. Chem. Educ. 1990, 67, 606.
J. Chem. Res. (S) 1984, 382.
22. Noyes, R. M., J. Am. Chem. Soc. 1980, 102, 4644.
19. Broxton, T. J.; Deady, L. W.; McCormack, J. D.; Kam, L. C.; Toh, S. H.,
23. Koros, E.; Kurin, K. From Phase Transitions Chaos; Gyorgyi, G., Ed.;
J. Chem. Soc., Perkin Trans. 1 1974, 1769.
World Science: Singapore, 1992; p 128, Chem. Abstr. 21 819u), 1993
20. Lee, J. G.; Cha, H. T.; Yoon, U. C.; Suh, Y. S.; Kim, C.; Park, I. S., Bull. 118.
Korean Chem. Soc. 1991, 12, 4.
James J. Harrison
Chevron Chemical Company, Richmond, CA, USA
A list of General Abbreviations appears on the front Endpapers