Bromine (pronEng|ˈbroʊmiːn/, /ˈbroʊmaɪn/, /ˈbroʊmɪn, _el. βρῶμος, "brómos", meaning "stench (of he-goats)" Gemoll W, Vretska K: Griechisch-Deutsches Schul- und Handwörterbuch ("Greek-German dictionary"), 9th ed., published by [http://www.oebvhpt.at/ öbvhpt] , ISBN 3-209-00108-1] ), is a
chemical elementwith the symbol Br and atomic number35. A halogenelement, bromine is a reddish-brown volatile liquid at standard room temperature that is intermediate in reactivity between chlorineand iodine. Bromine vapours are corrosiveand toxic. Approximately 556,000,000 kg were produced in 2007. Jack F. Mills "Bromine" in Ullmann's Encyclopedia of Chemical Technology Wiley-VCH Verlag; Weinheim, 2002. DOI: 10.1002/14356007.a04_391] The main applications for bromine are in fire retardants and fine chemicals.
Bromine was discovered independently by two chemists Antoine Balard and
Carl Jacob Löwigin 1825 and 1826.
Balard found bromide salts in the ash of sea weed from the
salt marshes of Montpellierin 1826. The seaweed was used to produce iodine, but also contained bromine. Carl Jacob Löwigworking at the laboratory of Leopold Gmelinproduced elemental bromine by reacting mineral salts, which contained bromides, with chlorine gas. The publication of the results was delayed and Balard published his results first.
Bromine was not produced in quantity until 1860. The French chemist and physicist
Joseph-Louis Gay-Lussacsuggested the name bromine due to the characteristic smell of the vapors. Some also suggest that it may have been discovered by Bernard Courtois, the man who discovered iodine. [cite web
url = http://www.vanderkrogt.net/elements/elem/br.html
title = Bromine
publisher = vanderkrogt.net ]
Potassium bromideand sodium bromidewere used as anticonvulsants and sedatives in the late 19th and early 20th centuries, until it was gradually superseded by chloral hydrateand then the barbiturates.
Bromine has 2 stable isotopes: Br-79 (50.69%) and Br-81 (49.31%). At least another 23 [cite book | author=GE Nuclear Energy | title=Chart of the Nuclides, 14th Edition | year=1989 ] isotopes are known to exist. Many of the bromine isotopes are fission products. Several of the heavier bromine isotopes from fission are delayed neutron emitters. All of the radioactive bromine isotopes are relatively short lived. The longest half life is the neutron deficient Br-77 at 2.376 days. The longest half life on the neutron rich side is Br-82 at 1.471 days. A number of the bromine isotopes exhibit metastable isomers. Stable Br-79 exhibits a radioactive isomer, with a half life of 4.86 seconds. It decay by isomeric transition to the stable ground state.
Bromine is the only liquid
nonmetallic element at room temperature, and one of only six elements on the periodic table that are liquid at or close to room temperature. The pure chemical element has the physical form of a diatomic molecule, Br2. It is a dense, mobile, reddish-brown liquid, that evaporates easily at standard temperature and pressures to give a red vapor (its color resembles nitrogen dioxide) that has a strong disagreeable odor resembling that of chlorine. Bromine is a halogen, and is less reactive than chlorineand more reactive than iodine. Bromine is slightly soluble in water, and highly soluble in carbon disulfide, aliphatic alcohols (such as methanol), and acetic acid. It bonds easily with many elements and has a strong bleaching action. Bromine, like chlorine, is also used in maintenance of swimming pools.
Certain bromine-related compounds have been evaluated to have an
ozone depletion potentialor bioaccumulate in living organisms. As a result many industrial bromine compounds are no longer manufactured, are being restricted, or scheduled for phasing out.
Bromine is a powerful
oxidizing agent. It reacts vigorously with metals, especially in the presence of water, as well as most organic compounds, especially upon illumination.
Bromine has no known role in human health. Organobromine compounds do occur naturally, a famous example being
Tyrian purple. Most organobromine compounds in nature arise via the action of vanadium bromoperoxidase.
Occurrence and production
:"See also ."The diatomic element Br2 does not occur naturally. Instead, bromine exists exclusively as bromide salts in diffuse amounts in crustal rock. Due to
leaching, bromide salts have accumulated in sea water (85 ppm), but at a lower concentration than chloride. Bromine may be economically recovered from bromide-rich brine wells and from the Dead Seawaters (up to 50000 ppm).
Approximately 556,000 metric tons (worth around US$2.5 billion) of bromine are produced per year (2007) worldwide with the
United States, China, and Israelbeing the primary producers. Bromine production has increased sixfold since the 1960s. The largest bromine reserve in the United States is located in Columbia and Union County, Arkansas, U.S. [ [http://www.cals.lib.ar.us/butlercenter/lesson_plans/lesson%20plans/Lesson%20plans-retained/Bromine.pdf Bromine:An Important Arkansas Industry] , Butler Center for Arkansas Studies] China's bromine reserves are located in the Shandong Provinceand Israel's bromine reserves are contained in the waters of the Dead Sea. The bromide-rich brines are treated with chlorine gas, flushing through with air. In this treatment, bromide anions are oxidized to bromine by the chlorine gas.
:2 Br− + Cl2 → 2 Cl− + Br2
Because of its commercial availability and long shelf-life, bromine is not typically prepared. Small amounts of bromine can however be generated through the reaction of solid
sodium bromidewith concentrated sulfuric acid(H2SO4). The first stage is formation of hydrogen bromide(HBr), which is a gas, but under the reaction conditions some of the HBr is oxidized further by the sulfuric acid to form bromine (Br2) and sulfur dioxide(SO2).:NaBr (s) + H2SO4 (aq) → HBr (aq) + NaHSO4 (aq):2 HBr (aq) + H2SO4 (aq) → Br2 (g) + SO2 (g) + 2 H2O (l)
Similar alternatives, such as the use of dilute
hydrochloric acidwith sodium hypochlorite, are also available. The most important thing is that the anionof the acid(in the above examples, sulfateand chloride, respectively) be more electronegativethan bromine, allowing the substitution reactionto occur.
Organic compounds are brominated by either addition or substitution reactions. Bromine undergoes electrophilic addition to the double-bonds of
alkenes, via a cyclic bromonium intermediate. In non-aqueous solvents such as carbon disulfide, this affords the di-bromo product. For example, reaction with ethylenewill produce 1,2-dibromoethane. Bromine also undergoes electrophilic addition to phenols and anilines. When used as bromine water, the corresponding bromohydrin is formed instead. So reliable is the reactivity of bromine that bromine water is employed as a reagent to test for the presence alkenes, phenols, and anilines. Like the other halogens, bromine participates in free radical reactions. For example hydrocarbons are brominated upon treatment with bromine in the presence of light.
Bromine, sometimes with a catalytic amount of
phosphorus, easily brominates carboxylic acids at the α-position. This method, the Hell-Volhard-Zelinsky reaction, is the basis of the commercial route to bromoacetic acid.
"N"-Bromosuccinimide is commonly used as a substitute for elemental bromine, being easier to handle, and reacting more mildly and thus more selectively.
Organic bromides are often preferable relative to the less reactive chlorides and more expensive iodide-containing reagents. Thus,
Grignardand organolithium compound are most often generated from the corresponding bromides.
Bromine is an oxidizer, and it will oxidize
iodideions to iodine, being itself reduced to bromide:: Br2 + 2 I− → 2 Br− + I2
Bromine will also oxidize metals and metaloids to the corresponding bromides.
Anhydrousbromine is less reactive toward many metals than hydrated bromine, however. Dry bromine reacts vigorously with aluminium, titanium, mercury as well as alkaline earths and alkali metals.
A wide variety of organobromine compounds are used in
industry. Some are prepared from bromine and others are prepared from hydrogen bromide, which is obtained by burning hydrogenin bromine.
Illustrative of the addition reaction [OrgSynth | author = N. A. Khan, F. E. Deatherage, and J. B. Brown | title = Stearolic Acid | collvol = 4 | collvolpages = 851| year = 1963 | prep = CV4P0851] is the preparation of
1,2-Dibromoethane, the organobromine compound produced in the largest amounts::C2H4 + Br2 → CH2BrCH2Br
Ethylene bromide is an additive in gasolines containing lead anti-
engine knockingagents. It scavenges lead by forming volatile lead bromide, which is exhausted from the engine. This application has declined since the 1970s due to environmental regulations. Ethylene bromide is also used as a fumigant, but again this application is declining. Brominated flame retardants represent a commodity of growing importance. Specific compound used produced for this purpose include tetrabromobisphenol A, decabromodiphenyl ether, and vinyl bromide.
The bromides of calcium, sodium, and zinc account for a sizable part of the bromine market. These salts form dense solutions in water that are used as
dyes, agrichemicals, and pharmaceuticals are organobromine compounds. 1-Bromo-3-chloropropane, 1-bromoethylbenzene, and 1-bromoalkanes are prepared by the antimarkovnikov addition of HBr to alkenes. Ethidium bromide, EtBr, is used as a DNAstain in gel electrophoresis.
* Bromine is also used in for the production of
brominated vegetable oil, which is used as an emulsifierin many citrus-flavored soft drinks.
Water purificationcompounds, Disinfectants
* Potassium bromide is used in some photographic developers to inhibit the formation of fog (undesired reduction of silver).
Elemental bromine is toxic and causes burns. As an
oxidizingagent, it is incompatible with most organic and inorganic compounds. Care needs to taken when transporting bromine, it is commonly carried in steel tanks lined with lead, supported by strong metal frames.
When certain ionic compounds containing bromine are mixed with potassium permanganate (KMnO4), they will form a pale brown cloud of bromine gas. This gas smells like bleach and is very irritating to the mucus membranes. Upon exposure, one should move to fresh air immediately. If symptoms arise, medical attention is needed.
* [http://periodic.lanl.gov/elements/35.html Los Alamos National Laboratory – Bromine]
* [http://www.webelements.com/webelements/elements/text/Br/index.html WebElements.com – Bromine]
* [http://www.theodoregray.com/PeriodicTable/Elements/035/index.s7.html Theodoregray.com – Bromine]
* [http://minerals.usgs.gov/minerals/pubs/commodity/bromine USGS Minerals Information: Bromine]
* [http://www.bsef.com/ Bromine Science and Environmental Forum (BSEF)]
* [http://twt.mpei.ac.ru/MAS/Worksheets/HEDH/5-5-14-43-54/Tab-5-5-14-54-BROMINE-Thermal.mcd Thermal Conductivity of BROMINE]
* [http://twt.mpei.ac.ru/MAS/Worksheets/HEDH/5-5-14-43-54/Tab-5-5-14-54-BROMINE-Viscosity.mcd Viscosity of BROMINE]
Wikimedia Foundation. 2010.