Cyanogen bromide

Structural formula
General
Surname	Cyanogen bromide
other names	Cyanogen bromide; Cyanobromide; Bromocyanide;
Molecular formula	BrCN
Brief description	colorless, volatile needles
External identifiers / databases
EC number	208-051-2
ECHA InfoCard	100.007.320
PubChem	10476
ChemSpider	10044
Wikidata	Q420258
properties
Molar mass	105.9 g mol −1
Physical state	firmly
density	2.02 g · cm -3
Melting point	52 ° C
boiling point	61.5 ° C
Vapor pressure	116 h Pa (20 ° C)
solubility	soluble in water with hydrolysis
safety instructions
H and P phrases	H: 300 + 310 + 330-314-400
	P: 280-260-301 + 330 + 331 + 310-303 + 361 + 353-304 + 340 + 310-305 + 351 + 338
Toxicological data	92 ppm · 10 min ( LC 50 , human , inh. )
Thermodynamic properties
ΔH f 0	140.5 kJ / mol
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cyanogen bromide is a derivative of hydrocyanic acid (HCN) in which the hydrogen atom has been replaced by bromine . Colloquially it is also called cyanide bromide or campilite .

Occurrence

A biosynthesis of cyanogen bromide was demonstrated in the Nitzschia cf pellucida , a diatom .

Presentation and extraction

Cyanogen bromide is prepared by reacting bromine with sodium cyanide in aqueous solution at temperatures below 20 ° C.

{\ displaystyle \ mathrm {Br_ {2} + NaCN \ longrightarrow NaBr + BrCN}}

Another synthesis starts from potassium thiocyanate or ammonium thiocyanate .

{\ displaystyle \ mathrm {SCN ^ {-} + 4 \ Br_ {2} +4 \ H_ {2} O \ longrightarrow \}}

{\ displaystyle \ mathrm {BrCN + 7 \ Br ^ {-} + SO_ {4} ^ {2 -} + 8 \ H ^ {+}}}

properties

2.7 g of cyanogen bromide

Cyanogen bromide is many times more toxic than potassium cyanide (KCN). Its extraordinary poisonous effect is based on the two components bromine and cyanide , which have both enzyme- inhibiting properties as a metabolic poison and also have a toxic effect on nerve cells.

Cyanogen bromide is in the form of volatile, colorless needles. With a molar heat of formation of 185.6 kJ / mol for cyanogen bromide vapor or 140.4 kJ / mol for the solid, it is an unstable endothermic compound. According to Antoine , the vapor pressure function results from log ₁₀ (P) = A− (B / (T + C)) (P in bar, T in K) with A = 3.53667, B = 727.385 and C = −130.052 in the temperature range from 273 K to 313 K.

The hydrolysis to sodium cyanate and sodium bromide takes place in sodium hydroxide solution . The reaction is strongly exothermic with a heat of reaction of −235 kJ mol ⁻¹ .

{\ displaystyle \ mathrm {BrCN + 2 \ OH ^ {-} \ longrightarrow CNO ^ {-} + Br ^ {-} + H_ {2} O}}

At higher temperatures and in the presence of aluminum bromide , trimerization to cyanuric bromide takes place .

The trimerization also occurs slowly at room temperature when the compound is stored for a long period of time.

structure

The BrCN molecule has a linear structure. The bond lengths of the Br – C bond or the C – N bond are typical of a C – Br single bond or C – N triple bond. The bond lengths are 1.789 Angstroms for the C – Br bond and 1.160 Angstroms for the C – N bond. The cyanogen bromide molecule is polar . The dipole moment is 2.94 D .

use

Cyanogen bromide is mainly used in gold leaching. In biochemistry it is used for the sequencing of proteins . Cyanogen bromide selectively cleaves the C-terminal after the amino acid methionine . The methionine reacts to form iminolactone, which is then acid-catalyzed hydrolysed to homoserine lactone . As a result, the protein is broken down into shorter fragments, which can be used with other analysis techniques e.g. B. Edman degradation can be analyzed.

safety instructions

Gaseous cyanogen bromide is hardly absorbed through the skin and well absorbed through the respiratory and digestive tract. It can be hydrolyzed or decomposed to hydrogen cyanide, hydrogen bromide , dicyan and cyanuric bromide on contact with water and stomach acid or on heating . Cyanogen bromide is very irritating to corrosive on the eyes, skin and mucous membranes. In contrast to hydrogen cyanide, it is perceived as irritating if it is present in the air from 1 ppm; The “endurance limit” is around 9 ppm.

Individual evidence

↑ Entry on cyanogen bromide. In: Römpp Online . Georg Thieme Verlag, accessed April 1, 2014.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Entry on cyanogen bromide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ Entry on cyanogen bromide in the ChemIDplus database of the United States National Library of Medicine (NLM) .
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-19.
↑ B. Vanelslander, C. Paul u. a .: Daily bursts of biogenic cyanogen bromide (BrCN) control biofilm formation around a marine benthic diatom. In: Proceedings of the National Academy of Sciences. 109, 2012, p. 2412, doi : 10.1073 / pnas.1108062109 .
^ KH Slotta: cyanogen bromide and anhydrous hydrocyanic acid in Chem. Ber. 67 (1934) 1028-1030. doi: 10.1002 / cber.19340670622 .
↑ Hartmann, WW, Dreger, EE: Cyanogen Bromide In: Organic Syntheses . 11, 1931, p. 30, doi : 10.15227 / orgsyn.011.0030 ; Coll. Vol. 2, 1943, p. 150 ( PDF ).
↑ W. König: Investigations from the organ. ‐ chem. Laboratory of the Technical University of Dresden. XCVII. About the reaction of rhodanides with bromine in aqueous solution . In: Journal for Practical Chemistry . tape 84 , no. 1 , September 1911, p. 558-560 , doi : 10.1002 / prac.19110840139 .
↑ ^a ^b ^c G. Lord, AA Woolf: The cyanogen halides. Part III. Their heats of formation and free energies . In: Journal of the Chemical Society (Resumed) . 1954, p. 2546-2551 , doi : 10.1039 / JR9540002546 .
↑ F. Oberhauser: The behavior of cyanogen bromide towards metal salts in Chem. Ber. 60 (1927) 1434-1439 doi: 10.1002 / cber.19270600628 .
↑ MI Grossmann: Cyanogen bromide danger in Chem. Eng. News 58 (1980) 43.
^ AG Smith, H. Ring, WV Smith, W. Gordy: Interatomic Distances and Nuclear Quadrupole Couplings in ClCN, BrCN, and ICN in Phys. Rev. 74 (1948) 370-372. doi: 10.1103 / PhysRev.74.370 .
↑ JK Tyler, J. Sheridan: Structural studies of linear molecules by microwave spectroscopy in Trans. Faraday Soc. 59 (1963) 2661-2670. doi: 10.1039 / TF9635902661 .

[roempp-1] Entry on cyanogen bromide. In: Römpp Online . Georg Thieme Verlag, accessed April 1, 2014.

[GESTIS-2] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Entry on cyanogen bromide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[ChemIDplus-3] Entry on cyanogen bromide in the ChemIDplus database of the United States National Library of Medicine (NLM) .

[CRC90_5_19-4] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-19.

[5] B. Vanelslander, C. Paul u. a .: Daily bursts of biogenic cyanogen bromide (BrCN) control biofilm formation around a marine benthic diatom. In: Proceedings of the National Academy of Sciences. 109, 2012, p. 2412, doi : 10.1073 / pnas.1108062109 .

[6] KH Slotta: cyanogen bromide and anhydrous hydrocyanic acid in Chem. Ber. 67 (1934) 1028-1030. doi: 10.1002 / cber.19340670622 .

[7] Hartmann, WW, Dreger, EE: Cyanogen Bromide In: Organic Syntheses . 11, 1931, p. 30, doi : 10.15227 / orgsyn.011.0030 ; Coll. Vol. 2, 1943, p. 150 ( PDF ).

[8] W. König: Investigations from the organ. ‐ chem. Laboratory of the Technical University of Dresden. XCVII. About the reaction of rhodanides with bromine in aqueous solution . In: Journal for Practical Chemistry . tape 84 , no. 1 , September 1911, p. 558-560 , doi : 10.1002 / prac.19110840139 .

[Lord-9] G. Lord, AA Woolf: The cyanogen halides. Part III. Their heats of formation and free energies . In: Journal of the Chemical Society (Resumed) . 1954, p. 2546-2551 , doi : 10.1039 / JR9540002546 .

[10] F. Oberhauser: The behavior of cyanogen bromide towards metal salts in Chem. Ber. 60 (1927) 1434-1439 doi: 10.1002 / cber.19270600628 .

[Grossmann-11] MI Grossmann: Cyanogen bromide danger in Chem. Eng. News 58 (1980) 43.

[12] AG Smith, H. Ring, WV Smith, W. Gordy: Interatomic Distances and Nuclear Quadrupole Couplings in ClCN, BrCN, and ICN in Phys. Rev. 74 (1948) 370-372. doi: 10.1103 / PhysRev.74.370 .

[13] JK Tyler, J. Sheridan: Structural studies of linear molecules by microwave spectroscopy in Trans. Faraday Soc. 59 (1963) 2661-2670. doi: 10.1039 / TF9635902661 .