Azodicarbonitrile

Structural formula
trans -form (left) and cis -form (right)
General
Surname	Azodicarbonitrile
other names	Azodicarboxylic acid dinitrile Dicyanodiazene Dicyanodiimide
Molecular formula	C 2 N 4
Brief description	orange crystals
External identifiers / databases
CAS number 1557-57-9 (mixture of isomers) 38055-41-3 ( trans isomer) 58729-63-8 ( cis isomer) Wikidata Q19259896
properties
Molar mass	80.0884 g mol −1
Physical state	firmly
Melting point	35–37.5 ° C (mixture of isomers) 50–55 ° C (mixture of isomers)
Vapor pressure	40 mmHg (20 ° C)
solubility	soluble in benzene, acetonitrile, ethyl acetate, nitromethane
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Azodicarbonitrile is a thermally unstable carbon-nitrogen compound with a nitrogen content of 70%, which can be assigned to the substance groups of azo compounds and nitriles . Azodicarbonitrile occurs in two isomeric forms with the trans and cis compounds .

Presentation and extraction

Azodicarbonitrile can be produced by a gas phase pyrolysis of cyanazide at 200 ° C via the cyanonitrile as an intermediate and nitrogen elimination .

${\displaystyle \mathrm {N_{3}CN\rightarrow NCN+N_{2}} }$

${\displaystyle \mathrm {N_{3}CN+NCN\rightarrow NC{-}N{=}N{-}CN+N_{2}} }$

A mixture of isomers is produced during the synthesis.

Another synthesis is based on cyanamide , which is converted into the sodium salt at −50 ° C using sodium methoxide in methanol . An oxidative reaction with tert-butyl hypochlorite at −50 ° C yields the intermediate sodium salt of N -chlorocyanamide . When heated, cyanonitrene is formed in the temperature range between 0 ° C and 10 ° C with elimination of sodium chloride , which dimerizes to form the target compound.

${\displaystyle \mathrm {H_{2}N{-}CN+NaOCH_{3}\rightarrow NaNH{-}CN+CH_{3}OH} }$

${\displaystyle \mathrm {NaNH{-}CN+H_{9}C_{4}OCl\rightarrow NaNCl{-}CN+C_{4}H_{9}OH} }$

${\displaystyle \mathrm {NaNCl{-}CN\rightarrow NCN+NaCl} }$

${\displaystyle \mathrm {2\ NCN\rightarrow NC{-}N{=}N{-}CN} }$

A mixture of isomers is also formed here.

properties

Azodicarbonitrile is a crystalline, orange colored and volatile substance. The melting points observed depend on the manufacturing method. A product made by gas phase pyrolysis melts at 35–37.5 ° C. A product obtained from cyanamide in solution melts at 50-55 ° C. The vapor pressures are around 8 mmHg at 0 ° C, 18 mmHg at 10 ° C and 40 mmHg at 20 ° C. The purification by means of distillation was carried out at temperatures below 0 ° C. and pressures below 1 Torr. Azodicarbonitrile can detonate in closed containers under mechanical stress or when heated. The compound is soluble in benzene , acetonitrile , ethyl acetate , nitromethane and 1,1,2-trichloro-1,2,2-trifluoroethane without decomposition . The solutions in water , methanol and diethyl ether are not stable. The ¹³ C-NMR spectrum shows only one signal at 118.3 ppm. In the IR spectrum , the CN vibration at 2200 cm ⁻¹ and the NN vibration at 1650 cm ^{−1 are} significant. Investigations by means of IR and Raman spectroscopy showed that the compound must be in the trans form. With the help of gas-phase electron diffraction measurements it was also found that the trans isomer is essentially present in the gas phase . The bond angle between the azo and cyano groups is 113 °. At 172 °, the cyano group is not completely linearly bound to the azo nitrogen.

Reactions

Azodicarbonitrile reacts smoothly with dienes to form 4,5-diazacyclohexenes. With 2,3-dimethylbutadiene , 1,2-dimethyl-4,5-dicyano-4,5-diazacyclohexene is formed by a [4 + 2] -cyloaddition, with cyclopentadiene 5,6-dicyano-5,6-diazabicyclo is formed [2.2.1] hepten and formed 1,2,3,4-tetrahydro-1,4- o -benzenophthalazine-2,3-dicarbonitrile with anthracene .

Individual evidence

1. ↑ ^{a b c d e f g h i j} F. D. Marsh, ME Hermes: Azodicarbonitrile. In: Journal of the American Chemical Society . 87, No. 8, 1965, pp. 1819-1820, doi : 10.1021 / ja01086a054 .
2. ↑ ^{a b c d e f} Mary Gail Kinzer Hutchins, Daniel Swern: Generation of Cyanonitren: Study of the Reaction of Sodium Hydrogen Cyanamide, tert-Butyl Hypochlorite, and Terniary Amines. In: The Journal of Organic Chemistry . 47, No. 25, 1982, pp. 4847-4850, doi : 10.1021 / jo00146a005 .
3. ↑ ^{a b c d} Børge Bak, Roar Eskildsen, Peter Jansen, Sigfrid Svensson, J. Koskikallio, Sukeji Kachi: Preparation of C ₂ N ₄ , Azodicarbonitrile. In: Acta Chemica Scandinavica. 25, 1971, pp. 3181-3181, doi : 10.3891 / acta.chem.scand.25-3181 ( pdf ).
4. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
5. ↑ PG Urben; MJ Pitt: Bretherick's Handbook of Reactive Chemical Hazards . 8th edition, Vol. 1, Butterworth / Heinemann 2017, ISBN 978-0-08-100971-0 , p. 239.
6. ↑ Bak, B .; Jansen, P .: The Symmetry of Azocarbonitrile in J. Mol. Struct. 11 (1972) 25-31, doi : 10.1016 / 0022-2860 (72) 85219-0 .
7. ↑ ^{a b} Almenningen, A .; Bak, B .; Jansen, P .; Strand, TG: Molecular Structure of Gaseous Cyanogen Azide and Azodicarbonitrile in Acta Chem. Scand. 27 (1973) 1531-1540, doi : 10.3891 / acta.chem.scand.27-1531 , pdf .