bromine


from Wikipedia, the free encyclopedia
properties
General
Name , symbol , atomic number Bromine, Br, 35
Element category Halogens
Group , period , block 17 , 4 , p
Appearance gaseous: red-brown
liquid: red-brown
solid: shiny metallic
CAS number 7726-95-6
EC number 231-778-1
ECHA InfoCard 100,028,890
Mass fraction of the earth's envelope 6.0 ppm
Atomic
Atomic mass 79.904 (79.901-79.907) and
Atomic radius (calculated) 115 (94) pm
Covalent radius 120 pm
Van der Waals radius 185 pm
Electron configuration [ Ar ] 3 d 10 4 s 2 4 p 5
1. Ionization energy 11.81381 (6) eV1 139.86 kJ / mol
2. Ionization energy 21st.591 eV2 083.2 kJ / mol
3. Ionization energy 34.871 (19) eV3 364.5 kJ / mol
4. Ionization energy 47.782 (12) eV4 610.3 kJ / mol
5. Ionization energy 59.595 (25) eV5 750 kJ / mol
6. Ionization energy 87.390 (25) eV8 431.9 kJ / mol
7. Ionization energy 103.03 (19) eV9 941 kJ / mol
Physically
Physical state liquid
Crystal structure orthorhombic
density 3.12 g cm −3 at 300 K.
magnetism diamagnetic ( Χ m = −2.8 10 −5 )
Melting point 265.8 K (−7.3 ° C)
boiling point 331.7 K (58.5 ° C)
Molar volume (solid) 19.78 10 −6 m 3 mol −1
Heat of evaporation 30 kJ / mol
Heat of fusion 5.8 kJ mol −1
Vapor pressure 2.2 · 10 4 Pa at 293 K.
Thermal conductivity 0.12 W m −1 K −1
Chemically
Oxidation states ± 1, 3, 5, 7
Normal potential 1.066 V (Br + e - → Br - )
Electronegativity 2.96 ( Pauling scale )
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP
77 Br {syn.} 57.036 h ε 1,365 77 Se
78 Br {syn.} 6.46 min ε 3,574 78 Se
79 Br 50.69  % Stable
80 Br {syn.} 17.68 min β - 2.004 80 kr
ε 1,871 80 se
81 Br 49.31% Stable
82 Br {syn.} 35.30 h β - 3.093 82 kr
83 Br {syn.} 2.40 h β - 0.972 83 kr
For other isotopes see list of isotopes
NMR properties
  Spin
quantum
number I
γ in
rad · T −1 · s −1
E r  ( 1 H) f L at
B = 4.7 T
in MHz
79 Br 3/2 6.73 · 10 7
81 Br 3/2 7.25 · 10 7
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
05 - Corrosive 06 - Toxic or very toxic 09 - Dangerous for the environment

danger

H and P phrases H: 330-314-400
P: 210-273-304 + 340-305 + 351 + 338-309 + 310-403 + 233
MAK

Switzerland: 0.1 ml m −3 or 0.7 mg m −3

Toxicological data
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Brom [ bʁoːm ] ( ancient Greek βρῶμος brōmos "stink") is a chemical element with the element symbol Br and the atomic number  35. In the periodic table it is in the 7th main group, or the 17th  IUPAC group and thus belongs together with fluorine , Chlorine , iodine , astatine and tenness to the halogens . Elemental bromine is present under normal conditions (temperature = 0 ° C and pressure = 1 atm) in the form of the diatomic molecule Br 2 in liquid form. Bromine and mercury are the only natural elements that are liquid under normal conditions.

In nature, bromine does not occur in elemental form, but only in various compounds. The most important compounds are the bromides , in which bromine occurs in the form of the anion Br - . The best known bromides are sodium bromide and potassium bromide . Bromides are a component of sea ​​water and have a number of biological functions.

discovery

Justus Liebig was the first to isolate elemental bromine

Bromine was extracted in 1826 by the French chemist Antoine-Jérôme Balard from seaweed in the salt marshes near Montpellier, who recognized it as a previously unknown substance.

Two years before Balard, the German chemist Justus von Liebig was unwittingly producing elemental bromine in 1824. He was commissioned to analyze the salt brines of Salzhausen , as the city was planning a spa . While examining this brine, Liebig found a new substance that he interpreted as iodine chloride . 13 years later he admitted that his negligent analysis had robbed him of the discovery of a new element. Liebig wrote: “I know a chemist who, when he was in Kreuznach, examined the mother liquors of the salt works.” He then went on to describe his mishap and concluded with the words: “Since that time he has not proposed any more theories, if they have not been supported and confirmed by undoubted experimentation; and I can report that he didn't do anything bad about it. "

Even Karl Lowig has dealt with bromine, which he before 1825 by introducing chlorine in Kreuznacher won brine water, but Balard beat him to it with the publication of his discovery.

Industrial production began in 1860. Because of its pungent smell, Joseph Louis Gay-Lussac suggested the name “Brom” ( Greek for “ buck stink of animals”).

Occurrence

Bromine occurs in the form of bromides, the salts of hydrobromic acid . In terms of quantity, the largest deposits are found as dissolved bromides in seawater. Natural salt deposits (rock and potash salts) also contain small amounts of potassium bromide and potassium bromate . Bromine can also occur in the atmosphere in the form of molecular bromine and bromine oxide and can have a significant influence on atmospheric ozone chemistry and can be transported over long distances. During the polar spring, larger concentrations (> 10ppt) of BrO regularly destroy almost all of the tropospheric ozone. These events can also be observed from satellites using the DOAS method. In tropical regions with high bioactivity, strong emissions of halogenated hydrocarbons have been observed, which can ultimately contribute to the formation of BrO and ozone depletion through photolysis.

Bromine is essential for animals in traces. Bromide acts as a cofactor in a metabolic reaction that is necessary to build up the IV collagen matrix in the connective tissue .

Extraction and presentation

Development of worldwide bromine production over time

The industrial production of elemental bromine takes place through the oxidation of bromide solutions with chlorine.

The oxidation of potassium bromide by chlorine produces bromine and potassium chloride

Brine and highly salty water from great depths as well as salt lakes and occasionally also sea water are used as bromide sources . Extraction from the residual liquors from potash extraction is no longer economical. Since 1961, the amount of bromine recovered annually has more than quintupled from around 100,000 tons to over half a million tons. The largest bromine producers are the United States, China, Israel, and Jordan.

In the laboratory, bromine can be produced by reacting sodium bromide with sulfuric acid and manganese dioxide in the heat. The bromine is separated off by distillation .

Of sodium bromide bromine, arise, manganese (IV) oxide and sulfuric acid, manganese (II) sulfate , sodium sulfate and water .

properties

Liquid bromine with vapor in ampoule

Physical Properties

The density of bromine is 3.12 g / cm 3 . The heavy red-brown liquid forms vapors that smell like chlorine and are more toxic than chlorine. Solid bromine is dark; it brightens as it cools down further. In water , it is moderate, organic solvents such as alcohols , carbon disulfide or carbon tetrachloride highly soluble. Bromine dissolved in water reacts slowly with the intermediate formation of hypobromous acid (HBrO) and the release of oxygen to form hydrogen bromide (HBr). The kinetically inhibited reaction is accelerated by (sun) light, so bromine water is stored in brown, less translucent bottles.

Chemical properties

Bromine behaves chemically like the lighter chlorine , but reacts less energetically in the gaseous state. Moisture greatly increases the reactivity of the bromine. In contrast to chlorine, it only reacts with hydrogen at higher temperatures to form hydrogen bromide (colorless gas).

It reacts exothermically with many metals (e.g. aluminum) to form the respective bromide. Only tantalum and platinum are resistant to wet bromine .

use

Bromine, demonstration sample for teaching purposes, kept safely
  • Chemical polishing of gallium arsenide (as a solution in methanol )
  • multi- brominated biphenyls or diphenyl ethers as flame retardants in composite materials such as FR-4 as used in printed circuit boards are used. In 2000, 38% of the bromine was used in the production of brominated flame retardants.
  • Methyl bromide as a pesticide
  • Disinfectant (milder than chlorine )
  • in the form of bromides, for example potassium bromide , as a drug rich in side effects ( narcosis , sedatives and sleeping pills; treatment of therapy-resistant epilepsy with generalized tonic-clonic seizures, earlier - for example also for the treatment of " hysteria " - very popular - now obsolete). In 1928, one of five prescriptions for drugs containing bromine was issued in the United States.
  • Photo industry (silver bromide as part of the light-sensitive suspension )
  • Alkali hypobromites as bleaching agents
  • in the laboratory as an indicator (unsaturated carbon compounds discolour bromine water, i.e. addition of bromine)
  • in chemistry class for the experimental demonstration of addition and substitution reactions
  • Bromates as oxidizing agents
  • Bromine-containing rubber for the production of "airtight" tires
  • Tear gas , e.g. B. in the form of monobromoacetone
  • in means of protection against the nerve agent soman in US soldiers in the Iraq war
  • Formerly in the form of alkyl bromides as a scavenger to remove lead from cylinders when using leaded petrol

proof

Bromide ions can be detected qualitatively with the help of chlorine water and hexane .

As with the other detection reactions for halides, the poor solubility of the silver salt of bromide can also be used for the wet-chemical detection of bromide ions . The same applies to the volumetric determination of the halides by titration .

To trace determination and speciation of bromide and bromate is ion chromatography used. In polarography , bromate shows a cathodic step at −1.78 V (versus SCE , in 0.1  mol / l KCl), where it is reduced to bromide. Traces of bromate can also be recorded using differential pulse polarography.

safety instructions

Elemental bromine is very toxic and highly corrosive, skin contact leads to chemical burns that are difficult to heal. Inhaled bromine vapors cause shortness of breath, pneumonia and pulmonary edema . Bromine is also toxic to aquatic organisms.

In the laboratory, when working with bromine, a three percent sodium thiosulphate solution is usually provided, as it can bind spilled bromine or hydrogen bromide very well. Here, form sodium bromide , elemental sulfur and sulfuric acid . The resulting acid can break down further thiosulphate into sulfur and sulfur dioxide:

Bromine is stored in containers made of glass , lead , Monel , nickel or Teflon .

links

Spongiadioxin A , a natural organobromine compound

→ Category: bromine compound

Bromine forms compounds in various oxidation states from −1 to +7. The most stable and most common oxidation state is −1, the higher ones are only formed in compounds with the more electronegative elements oxygen , fluorine and chlorine . The odd oxidation states +1, +3, +5 and +7 are more stable than the even ones.

Hydrogen bromide and bromides

Inorganic compounds in which the bromine is in the −1 oxidation state and thus as an anion are called bromides . These are derived from the gaseous hydrogen compound hydrogen bromide (HBr). This is a strong acid and easily releases the proton in aqueous solutions . Bromides are generally readily soluble in water, exceptions are silver bromide , mercury (I) bromide and lead (II) bromide .

The bromides of the alkali metals , especially sodium bromide , are particularly well known . Also potassium bromide is used in large quantities, mainly as a fertilizer and for the production of other potassium compounds.

Lead bromide used to be released in large quantities when leaded fuel was burned (if dibromomethane was added to gasoline to make the lead volatile, see tetraethyl lead # Combustion in the engine ).

Bromine oxides

A large number of compounds of bromine and oxygen are known. These are based on the general formulas BrO x (x = 1–4) and Br 2 O x (x = 1–7). Two of the bromine oxides, dibromotrioxide (Br 2 O 3 ) and dibromopentaoxide (Br 2 O 5 ) can be isolated as solids.

Bromine Acids

In addition to the bromine oxides, bromine and oxygen also form several acids in which a bromine atom is surrounded by one to four oxygen atoms. These are hypobromous acid , bromous acid , bromic acid and perbromic acid . As a pure substance, they are unstable and only known in aqueous solution or in the form of their salts.

Interhalogen compounds

Bromine forms a number of interhalogen compounds mainly with fluorine , and in some cases with the other halogens as well . Bromfluoride as bromine fluoride and bromine trifluoride have a strong oxidizing and fluoriend. While bromine is the more electropositive element in the fluorine-bromine and chlorine-bromine compounds in oxidation states +1 in bromine chloride to +5 in bromine pentafluoride , it is the more electronegative component in compounds with iodine . With this element the compounds iodobromide and iodotribromide are known.

Organic bromine compounds

A large number of organic bromine compounds (also organobromine compounds ) are produced synthetically. The bromoalkanes , the bromoalkenes and the bromoaromatics are important . They are used, among other things, as solvents, refrigerants , hydraulic oils , pesticides, flame retardants or pharmaceuticals.

The organobromine compounds also include the polybrominated dibenzodioxins and dibenzofurans .

literature

Web links

Wiktionary: Brom  - explanations of meanings, word origins, synonyms, translations
Commons : Brom  - album with pictures, videos and audio files

Individual evidence

  1. ^ Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
  2. The values ​​for the properties (infobox) are taken from webelements.com (bromine) , unless otherwise stated .
  3. The standard value recommended by IUPAC is given, since the isotopic composition of this element can vary locally, the mass range given in brackets results for the mean atomic weight. IUPAC, Standard Atomic Weights Revised 2013 ( ciaaw.org ).
  4. a b c d e f g Entry on bromine in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 11, 2020.
  5. a b c d e f g Entry on bromine at WebElements, https://www.webelements.com , accessed on June 11, 2020.
  6. a b c d e Entry on bromine in the GESTIS substance database of the IFA , accessed on August 9, 2016(JavaScript required) .
  7. Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values ​​there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
  8. a b Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values ​​for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data. 56, 2011, pp. 328-337 ( doi: 10.1021 / je1011086 ).
  9. Entry on bromine in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on August 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  10. Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 7726-95-6 or bromine ), accessed on November 2, 2015.
  11. a b Gigiena i Sanitariya. (English translation HYSAAV. ), Vol. 35 (11), 1970, p. 11.
  12. a b c Entry on bromine in the ChemIDplus database of the United States National Library of Medicine (NLM) .
  13. a b W. B. Deichmann: Toxicology of Drugs and Chemicals. Academic Press, New York 1969, p. 645.
  14. ^ Sights in Bad Salzhausen ( Memento from February 18, 2008 in the Internet Archive ).
  15. ^ WH Brock: Justus von Liebig: a biography of the great scientist and European. Vieweg Verlag, Braunschweig 1999.
  16. J. Liebig: About Laurent's theory of organic compounds. 1838, p. 554.
  17. TK Langebner: Justus von Liebig and the "Handbook of Chemistry", II. ( Memento from December 2, 2008 in the Internet Archive ) In: ÖAZ aktuell. Main article 17/2001.
  18. ^ Wilhelm Gemoll , Karl Vretska: Greek-German school and hand dictionary. 9th edition. Verlag Hölder-Pichler-Tempsky, ISBN 3-209-00108-1
  19. ^ A. Scott McCall et al: Bromine Is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture. In: Cell . 157 (6), 2014, pp. 1380-1392; doi: 10.1016 / j.cell.2014.05.009 .
  20. Stephen M. Jasinski: 2006 Minerals Yearbook. (PDF; 56 kB) United States Geological Survey , November 2007, accessed on September 17, 2011 (English).
  21. Mineral Commodity Summaries 2011. (PDF; 27 kB) United States Geological Survey, January 24, 2011, accessed on September 17, 2011 (English).
  22. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 440.
  23. Linda S. Birnbaum, Daniele F. Staskal: Brominated Flame Retardants: Cause for Concern? In: Environ Health Perspect . 112, 2004, pp. 9-17. doi: 10.1289 / ehp.6559 . PMC 1241790 (free full text)
  24. ^ Ann Dally: Women under the knife. A history of surgery. New York 1991, p. 187.
  25. Hans Bangen: History of the drug therapy of schizophrenia. Berlin 1992, ISBN 3-927408-82-4 , p. 22.
  26. ^ Klaus Ruppersberg: Bromine in school . In: News from chemistry . tape 63 , no. 5 . Wiley, Weinheim April 29, 2015, p. 540-542 , doi : 10.1002 / nadc.201590166 , urn : nbn: de: 0111-pedocs-122991 .
  27. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , pp. 487-488.