Hydrogen bromide

Structural formula
General
Surname	Hydrogen bromide
other names	Hydrogen bromide; Broman;
Molecular formula	HBr
Brief description	colorless gas that smokes in moist air and has a pungent odor
External identifiers / databases
EC number	233-113-0
ECHA InfoCard	100.030.090
PubChem	260
Wikidata	Q2447
properties
Molar mass	80.91 g · mol -1
Physical state	gaseous
density	3.6452 kg m −3 (0 ° C, 1013 h Pa )
Melting point	−86.86 ° C
boiling point	−66.4 ° C
Vapor pressure	2.00 M Pa (20 ° C)
pK s value	−8.9
solubility	good in water (700 g l −1 at 20 ° C)
Dipole moment	0.8272 (3) D (2.76 * 10 -30 C * m )
safety instructions
H and P phrases	H: 331-314-280
	EUH: 071
	P: 260-280-303 + 361 + 353-304 + 340-305 + 351 + 338-315-403-405
MAK	Switzerland: 2 ml m −3 or 6.7 mg m −3
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Hydrogen bromide is a colorless gas which forms mist in moist air because the combination of bromine and hydrogen dissolves well in water with the formation of hydrobromic acid .

Presentation and extraction

The industrial production of hydrogen bromide takes place by reacting bromine with an excess of hydrogen at 500 ° C. The process temperature can be reduced to 375 ° C in the presence of platinum catalysts. Another important source of hydrogen bromide is bromination on aromatic compounds, where the compound is obtained as a by-product. An electrophilic substitution reaction takes place on the aromatic. One example is the reaction of toluene with bromine. When heated or exposed to light, the bromine reacts with the toluene and the like. a. to benzyl bromide and hydrogen bromide, whereby the liquid, which was previously brown, is discolored.

Toluene and bromine react to form benzyl bromide and hydrogen bromide

Hydrogen bromide can also be released from sodium bromide. For this purpose, concentrated phosphoric acid is added dropwise to the solid at a slightly elevated temperature.

{\ displaystyle \ mathrm {2 \ NaBr \ + \ H_ {3} PO_ {4} \ {\ xrightarrow {\ Delta T}} \ 2 \ HBr \ uparrow + \ Na_ {2} HPO_ {4}}}

Sodium bromide reacts with phosphoric acid to form hydrogen bromide and disodium hydrogen phosphate

Alternatively, acetic acid can be used instead of phosphoric acid:

{\ displaystyle \ mathrm {NaBr + CH_ {3} COOH \ longrightarrow CH_ {3} COONa + HBr}}

Reaction with water

If hydrogen bromide is dissolved in water, the hydrogen bromide molecule dissociates and oxonium and bromide ions are formed. As a result, the pH drops and the solution reacts as a strong acid.

{\ displaystyle \ mathrm {H_ {2} O + HBr \ longrightarrow H_ {3} O ^ {+} + Br ^ {-}}}

use

By radical addition of hydrogen bromide to styrene can 2-bromoethyl benzene are obtained.

safety instructions

Hydrogen bromide gas is irritating to the eyes and respiratory tract due to the formation of acids in water and, in high concentrations, also toxic . (Gas) poisoning is rare, however, because it is mostly used as an aqueous solution (see above) and quickly forms fog after possible outgassing . When organic substances containing bromine are completely burned , elemental bromine, which is much more toxic, can also be formed in addition to hydrogen bromide.

Individual evidence

↑ Entry on hydrogen bromide. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
↑ ^a ^b ^c ^d ^e ^f ^g Entry on hydrogen bromide, anhydrous in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
↑ Eberhard Gerdes: Qualitative Inorganic Analysis: A Companion for Theory and Practice . Springer DE, 2000, ISBN 3-540-67875-1 , pp. 154 ( limited preview in Google Book search).
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Dipole Moments, pp. 9-51.
↑ Entry on Hydrogen bromide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 10035-10-6 or hydrogen bromide ), accessed on November 2, 2015.
↑ ^a ^b ^c Yoffe, D .; Frim, R .; Ukeles, SD; Dagani, MJ; Barda, HJ; Benya, TJ; Sanders, DC: Bromine Compounds , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a04_405.pub2 .
↑ G. Brauer (Ed.), Handbook of Preparative Inorganic Chemistry 2nd Edition, Volume 1, Academic Press 1963, pp. 282-6.
^ Entry on hydrogen bromide in the Hazardous Substances Data Bank , accessed November 28, 2018.

[roempp-1] Entry on hydrogen bromide. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.

[GESTIS-2] ↑ ^a ^b ^c ^d ^e ^f ^g Entry on hydrogen bromide, anhydrous in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

[Eberhard_Gerdes-3] Eberhard Gerdes: Qualitative Inorganic Analysis: A Companion for Theory and Practice . Springer DE, 2000, ISBN 3-540-67875-1 , pp. 154 ( limited preview in Google Book search).

[CRC90_9_51-4] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Dipole Moments, pp. 9-51.

[CLP_100.030.090-5] Entry on Hydrogen bromide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[6] Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 10035-10-6 or hydrogen bromide ), accessed on November 2, 2015.

[Ullmann-7] Yoffe, D .; Frim, R .; Ukeles, SD; Dagani, MJ; Barda, HJ; Benya, TJ; Sanders, DC: Bromine Compounds , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a04_405.pub2 .

[8] G. Brauer (Ed.), Handbook of Preparative Inorganic Chemistry 2nd Edition, Volume 1, Academic Press 1963, pp. 282-6.

[HSDB-9] Entry on hydrogen bromide in the Hazardous Substances Data Bank , accessed November 28, 2018.