Phenyl azide

Phenyl azide is an organic compound with the formula C6H5N3. It is one of the prototypical organic azides. It is a pale yellow oily liquid with a pungent odor. The structure consists of a linear azide substituent bound to a phenyl group. The C−N=N angle is approximately 120°. It was discovered in 1864 by Peter Griess by the reaction of ammonia and phenyldiazonium.[2][3]

Phenyl azide
Skeletal formula
Ball-and-stick model
Ball-and-stick model
Space-filling model
Space-filling model
Names
Preferred IUPAC name
Azidobenzene[1]
Other names
Phenyl azide[1]
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.009.756
EC Number
  • 210-730-3
MeSH C014747
UNII
  • InChI=1S/C6H5N3/c7-9-8-6-4-2-1-3-5-6/h1-5H ☒N
    Key: CTRLRINCMYICJO-UHFFFAOYSA-N ☒N
  • InChI=1/C6H5N3/c7-9-8-6-4-2-1-3-5-6/h1-5H
    Key: CTRLRINCMYICJO-UHFFFAOYAH
  • [N-]=[N+]=NC1=CC=CC=C1
Properties
C6H5N3
Molar mass 119.127 g·mol−1
Appearance Pale yellow, oily liquid
Boiling point 49 to 50 °C (120 to 122 °F; 322 to 323 K) at 5 mmHg
not appreciable
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 explosive
Related compounds
Related compounds
 Aniline
Nitrobenzene
Nitrosobenzene
Phenylhydrazine
Phenylhydroxylamine
Diazonium cation
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Phenyl azide is prepared by the diazotization of phenylhydrazine with nitrous acid:[4]

C6H5NHNH2 + HNO2 → C6H5N3 + 2 H2O

Aryl iodides bearing electron-withdrawing substituents undergo metathesis with sodium azide in the presence of Cu(I), sodium ascorbate, and N,N'-dimethylethane-1,2-diamine (DMEDA):[5]

RC6H4I + NaN3 → RC6H4N3 + NaI

It can also be prepared by condensation of benzenediazonium salt with toluenesulfonamide, followed by hydrolysis.

Chemical reactions

Phenyl azide cycloadds to alkenes and especially alkynes, particularly those bearing electronegative substituents. In a classic example of click chemistry, phenyl azide and phenylacetylene react to give diphenyl triazole.

Phenyl azide reacts with triphenylphosphine to give the Staudinger reagent triphenylphosphine phenylimide (C6H5NP(C6H5)3).

Thermolysis induces loss of N2 to give the highly reactive phenylnitrene C6H5N.[6]

Safety

As with many other azides, phenyl azide poses a risk of explosion,[4] so a protective blast shield is recommended during purification and handling. Distillations are hazardous. Organic Syntheses recommends a vacuum of 5mm Hg to give a boiling point of "66–68 °C/21 mm. with a bath temperature of 70–75 °C."[4] The pure substance may be stored in the dark, cold, and even then the shelf-life is only weeks.

References
  1. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 66, 1119. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. Griess, John Peter; Hofmann, August Wilhelm Von (1864-01-01). "XX. On a new class of compounds in which nitrogen is substituted for hydrogen". Proceedings of the Royal Society of London. 13: 375–384. doi:10.1098/rspl.1863.0082. S2CID 94746575.
  3. Griess, Peter (1866). "Ueber eine neue Klasse organischer Verbindungen, in denen Wasserstoff durch Stickstoff vertreten ist". Annalen der Chemie und Pharmacie (in German). 137 (1): 39–91. doi:10.1002/jlac.18661370105.
  4. R. O. Lindsay and C. F. H. Allen (1942). "Phenyl azide". Organic Syntheses. 22: 96. doi:10.15227/orgsyn.022.0096.
  5. Andersen, Jacob; Madsen, Ulf; Björkling, Fredrik; Liang, Xifu (2005). "Rapid Synthesis of Aryl Azides from Aryl Halides under Mild Conditions". Synlett. 2005 (14): 2209–2213. doi:10.1055/s-2005-872248. ISSN 0936-5214.
  6. W. H. Pearson, P. S. Ramamoorthyin "Phenyl Azide" Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289X.
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