About Bromine [Br] Element

Characteristics

An: 35 N: 45

Am: 79.904 g/mol

Group No: 17

Group Name: Halogen

Block: p-block Period: 4

State: liquid

Colour: red-brown, metallic lustre when solid Classification: Non-metallic

Boiling Point: 332K (59^oC)

Melting Point: 265.8K (-7.3^oC)

Critical temperature: 586K (313^oC)

Density: (liquid) 3.1028g/cm³

Discovery Information

Who: Antoine J. Balard

When: 1826

Where: France

Name Origin

Greek: bromos (stench). "Bromine" in different languages.

Sources

Occurs in compounds in sea water. World wide production is around 330 thousand tons per year. Main producers are the USA, Israel, the UK, Russia, France and Japan.

Abundance

Universe: 0.007 ppm (by weight)

Carbonaceous meteorite: 1.2 ppm

Earth’s Crust: 3 ppm

Seawater: 67.3 ppm

Human: 2900 ppb by weight; 230 ppb by atoms

Uses

Used for water purification (swimming pools), manufacture of ethylene dibromide (C₂H₄Br₂)(anti-knocking gasoline), bleaching, organic synthesis, solvent, analytical reagent, fire retardant for plastics, pharmaceuticals, shrink-proofing wool.

Bromine is used to make brominated vegetable oil, which is used as an emulsifier in many citrus-flavoured soft drinks.

History

Bromine was discovered by Antoine Balard at the salt marshes of Montpellier in 1826, but was not produced in quantity until 1860. The French chemist and physicist Joseph-Louis Gay-Lussac suggested the name bromine due to the characteristic smell of the vapours.

Notes

Bromine is highly reactive and is a powerful oxidizing agent in the presence of water. It reacts vigorously with amines, alkenes and phenols as well as aliphatic and aromatic hydrocarbons, ketones and acids (these are brominated by either addition or substitution reactions). With many of the metals and elements, anhydrous bromine is less reactive than hydrated bromine; however, dry bromine reacts vigorously with aluminium, titanium, mercury as well as alkaline earth metals and alkali metals.

Because of its high cost, bromine is usually recycled rather than disposed of into the environment.

About 500 million kilograms of bromine are produced each year worldwide, with the USA and Israel being the main producers.

Hazards

May be fatal if inhaled, highly toxic b inhalation, ingestion or skin contact. Elemental bromine is a strong irritant and, in concentrated form, will produce painful blisters on exposed skin and especially mucous membranes. Even low concentrations of bromine vapour (from 10 ppm) can affect breathing, and inhalation of significant amounts of bromine can seriously damage the respiratory system.

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Bromine Compounds

Ammonium bromide NH₄Br

Used in manufacturing photographic chemicals and emulsion. It is also used as a flame retardant.

Lithium bromide LiBr

An extremely hygroscopic and oftern used as a dessicant. Along with lithium chloride (LiCl), it is frequently used in air conditioning and industrial drying systems.

Reactions of Bromine

Reactions with water

Bromine reacts with water to produce hypobromite, OBr^-. The pH of the solution determines the position of the equilibrium.

Br_2(l) + H₂O_(l) --> OBr^-_(aq) + 2H⁺_(aq) + Br^-_(aq)

Reactions with air

Bromine is not reactive towards oxygen or nitrogen but it will react ozone at -78^oC to form the unstable compound bromine(IV) oxide.

Br_2(l) + 2O_3(g) --> O_2(g) + 2BrO_2(s)

Reactions with halogens

Bromine reacts with chlorine in the gas phase to form the interhalogen species BrF. The product is difficult to obtain pure since BrF disproportionates at room temperature to form bromine, Br₂, and BrF₃ and BrF₅.

Br_2(g) + F_2(g) --> 2BrF_(g)

3BrF_(g) + Br_2(l) --> BrF_3(l)

5BrF_(g) + 2Br_2(l) --> BrF_5(l)

Under more forceful conditions, excess fluorine reacts with bromine at 150^oC to form the interhalogen species BrF₅.

Br_2(l) + 5F_2(g) --> 2BrF_5(l)

Chlorine reacts with bromine in the gas phase to form the unstable interhalogen species bromine(I) chloride, ClBr.

Cl_2(g) + Br_2(g) --> 2ClBr_(l)

Bromine reacts with iodine at room temperature to form the interhalogen species bromine(I) iodide, BrI.

Br_2(l) + I_2(s) --> 2IBr_(s)

Reactions with bases

Bromine reacts with hot aqueous alkali to produce bromate. Only one sixth of the total bromine is converted in this reaction.

3Br_2(g) + 6OH^-_(aq) --> BrO₃^-_(aq) + 5Br^-_(aq) + 3H₂O

Occurrence and Production of Bromine

Bromine occurs in nature as bromide salts in very diffuse amounts in crustal rock. Due to leaching, bromide salts have accumulated in sea water (85 ppm), and may be economically recovered from brine wells and the Dead Sea (up to 5000 ppm).

Approximately 500,000 metric tons (worth around US$350 million) of bromine are produced per year (2001) worldwide with the United States and Israel being the primary producers. The largest bromine reserve in the United States is located in Columbia and Union County, Arkansas. Israel’s bromine reserves are contained in the waters of the Dead Sea.

Isotopes of Bromine

⁷⁹Br [44 neutrons]

Abundance: 50.69%

Stable with 44 neutrons

⁸¹Br [46 neutrons]

Abundance: 49.31%

Stable with 46 neutrons