Cyanogen halides

Cyanogen halides are chemical compounds with the general formula X – C≡N, where X represents a halogen . They thus correspond to the nitriles and are important starting materials for the synthesis of carbonic acid derivatives. They can be understood as acid halides of cyanic acid .

presentation

Cyanogen halides can be produced by the action of halogens on metal cyanides or by halogenating hydrocyanic acid .

${\displaystyle {\ce {MCN + X2 -> XCN + MX}}}$

M = metal, X = halogen

Cyanogen fluoride can be obtained by thermal decomposition of cyanuric fluoride .

properties

Cyanogen halides are stable at normal pressure below 20 ° C and in the absence of moisture or acids. In the presence of free halogens or Lewis acids, they easily polymerize to form cyanuric halides, for example cyanogen chloride to form cyanuric chloride . They are very poisonous and irritating to tears. Cyanogen chloride melts at -6 ° C and boils at around 150 ° C. Cyanogen bromide melts at 52 ° C and boils at 61 ° C. Cyanide iodine sublimates at normal pressure. Cyanogen fluoride boils at −46 ° C and polymerizes to cyanuric fluoride at room temperature. In some of their reactions they are similar to the halogens. The hydrolysis of the cyanogen halides takes place in different ways, depending on the electronegativity of the halogens and the resulting different polarity of the XC bond.

${\displaystyle {\ce {XCN + 2NaOH -> NaOCN + NaX + H2O}}}$

(X = F, Cl)

${\displaystyle {\ce {XCN + 2NaOH -> NaOX + NaCN + H2O}}}$

(X = Br, I)

use

Cyanogen halides, especially cyanogen chloride and cyanogen bromide, are important starting materials for the introduction of the cyano group, the production of other carbonic acid derivatives and of heterocycles .

Individual evidence

1. ↑ ^{a b c} C.R. Noller: Textbook of Organic Chemistry . Springer-Verlag, 2013, ISBN 978-3-642-87324-9 , pp. 335 ( limited preview in Google Book search).
2. ↑ ^{a b} Houben-Weyl Methods of Organic Chemistry Vol. VIII, 4th Edition Peroxides, Carbonic Acid Derivatives, Carboxylic Acids, Carboxylic Acid Derivatives . Georg Thieme Verlag, 2014, ISBN 978-3-13-180534-8 , p. 90 ( limited preview in Google Book search).
3. ↑ ^{a b} Georg Brauer (Ed.), With the collaboration of Marianne Baudler u a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 227.
4. ↑ ^{a b c} Houben-Weyl Methods of Organic Chemistry Vol. E 4, 4th Edition Supplement Carbonic Acid Derivatives . Georg Thieme Verlag, 2014, ISBN 3-13-181144-7 , p. 915 ( limited preview in Google Book search).
5. ↑ Spektrum.de: Halogencyane - Lexicon of Chemistry - Spectrum of Science , accessed on January 22, 2017.