Hydrogen cyanide

Hydrogen cyanide
Ball and stick model of hydrogen cyanide
Ball and stick model of hydrogen cyanide
Spacefill model of hydrogen cyanide
Spacefill model of hydrogen cyanide
Names
IUPAC name
Formonitrile[2][3]
Systematic IUPAC name
Methanenitrile[3]
Other names
  • Formic anammonide
  • Hydridonitridocarbon[1]
  • Hydrocyanic acid (aqueous)
  • Hydrogen cyanide (gas form)
  • Prussic acid
  • Cyanane
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChemSpider
ECHA InfoCard 100.000.747 Edit this at Wikidata
EC Number
  • 200-821-6
KEGG
MeSH Hydrogen+Cyanide
RTECS number
  • MW6825000
UNII
UN number 1051
  • InChI=1S/CHN/c1-2/h1H ☒N
    Key: LELOWRISYMNNSU-UHFFFAOYSA-N ☒N
  • C#N
Properties
HCN
Molar mass 27.0253 g/mol
Appearance Colorless liquid or gas
Odor Almond-like[4]
Density 0.6876 g/cm3[5]
Melting point −13.29 °C (8.08 °F; 259.86 K)[5]
Boiling point 26 °C (79 °F; 299 K)[5]: 4.67 
Miscible
Solubility in ethanol Miscible
Vapor pressure 100 kPa (25 °C)[5]: 6.94 
75 μmol Pa−1 kg−1
Acidity (pKa) 9.21 (in water),

12.9 (in DMSO)[6]

Basicity (pKb) 4.79 (cyanide anion)
Conjugate acid Hydrocyanonium
Conjugate base Cyanide
1.2675[7]
Viscosity 0.183 mPa·s (25 °C)[5]: 6.231 
Structure
tetragonal (>170 K)
orthorhombic (<170 K)[8]
C∞v
Linear
2.98 D
Thermochemistry
35.9 J K−1 mol−1 (gas)[5]: 5.19 
201.8 J K−1 mol−1
135.1 kJ mol−1
Hazards
GHS labelling:
GHS02: Flammable GHS06: Toxic GHS08: Health hazard GHS09: Environmental hazard
Danger
H225, H300, H310, H319, H330, H336, H370, H410
P210, P261, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
4
4
2
Flash point −17.8 °C (0.0 °F; 255.3 K)
538 °C (1,000 °F; 811 K)
Explosive limits 5.6% – 40.0%[9]
Lethal dose or concentration (LD, LC):
501 ppm (rat, 5 min)
323 ppm (mouse, 5 min)
275 ppm (rat, 15 min)
170 ppm (rat, 30 min)
160 ppm (rat, 30 min)
323 ppm (rat, 5 min)[10]
200 ppm (mammal, 5 min)
36 ppm (mammal, 2 hr)
107 ppm (human, 10 min)
759 ppm (rabbit, 1 min)
759 ppm (cat, 1 min)
357 ppm (human, 2 min)
179 ppm (human, 1 hr)[10]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 10 ppm (11 mg/m3) [skin][9]
REL (Recommended)
ST 4.7 ppm (5 mg/m3) [skin][9]
IDLH (Immediate danger)
50 ppm[9]
Related compounds
Related alkanenitriles
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Hydrogen cyanide (also known as prussic acid) is a chemical compound with the formula HCN and structural formula H−C≡N. It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at 25.6 °C (78.1 °F). HCN is produced on an industrial scale and is a highly valued precursor to many chemical compounds ranging from polymers to pharmaceuticals. Large-scale applications are for the production of potassium cyanide and adiponitrile, used in mining and plastics, respectively.[11] It is more toxic than solid cyanide compounds due to its volatile nature.

Whether hydrogen cyanide is an organic compound or not is a topic of debate among chemists, and opinions vary from author to author. Traditionally, it is considered inorganic by significant part of authors. Contrary to them, it is considered organic by other authors, because hydrogen cyanide belongs to the class of organic compounds known as nitriles which have the formula R−C≡N, where R is typically organyl group (e.g., alkyl or aryl) or hydrogen.[12] In the case of hydrogen cyanide, the R group is hydrogen H, so the other names of hydrogen cyanide are methanenitrile and formonitrile.[3]

  1. ^ "hydrogen cyanide (CHEBI:18407)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute. 18 October 2009. Main. Retrieved 2012-06-04.
  2. ^ "Hydrogen Cyanide – Compound Summary". PubChem Compound. United States: National Center for Biotechnology Information. 16 September 2004. Identification. Retrieved 2012-06-04.
  3. ^ a b c "Hydrogen Cyanide".
  4. ^ https://apps.who.int/iris/rest/bitstreams/50961/retrieve[bare URL]
  5. ^ a b c d e f Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. ISBN 978-1439855119.
  6. ^ Evans DA. "pKa's of Inorganic and Oxo-Acids" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved June 19, 2020.
  7. ^ Patnaik P (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 978-0070494398.
  8. ^ Schulz, Axel; Surkau, Jonas (2022-09-21). "Main group cyanides: from hydrogen cyanide to cyanido-complexes". Reviews in Inorganic Chemistry. 43 (1). Walter de Gruyter GmbH: 49–188. doi:10.1515/revic-2021-0044. ISSN 0193-4929.
  9. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0333". National Institute for Occupational Safety and Health (NIOSH).
  10. ^ a b "Hydrogen cyanide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  11. ^ Gail, E.; Gos, S.; Kulzer, R.; Lorösch, J.; Rubo, A.; Sauer, M. "Cyano Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_159.pub2. ISBN 978-3527306732.
  12. ^ "Human Metabolome Database: Showing metabocard for Hydrogen cyanide (HMDB0060292)".

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