Hydrogen cyanide
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| Hydrogen cyanide | |
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| Missing image Hydrogen_cyanide_structure.png Chemical structure of hydrogen cyanide | |
| General | |
| Other names | Hydrocyanic acid Prussic acid formonitrile formic anammonide carbon hydride nitride cyclon |
| Molecular formula | HCN |
| Molar mass | 27.03 g/mol |
| Appearance | colorless gas or pale blue highly volatile liquid |
| CAS number | [74-90-8] |
| EINECS number | 200-821-6 |
| Properties | |
| Density and phase | 0.687 g/cm3, liquid |
| Solubility in water | completely miscible |
| Solubility in alcohol | miscible |
| Solubility in ether | slightly soluble |
| Melting point | −13.4°C (260 K) |
| Boiling point | 26°C (299 K) |
| Acidity (pKa) | 9.2 to 9.3 |
| Structure | |
| Molecular shape | linear |
| Dipole moment | ? D |
| Safety data | |
| EU classification | Highly flammable (F+) Very toxic (T+) Dangerous for the environment (N) |
| R-phrases | R12, R26, R50/53 |
| S-phrases | S1/2, S7/9, S16, S36/37 S38, S45, S60, S61 |
| PEL (US, OSHA) | 11 mg/m3 |
| IDLH (US, NIOSH) | 55 mg/m3 |
| Flash point | −17.78°C |
| Autoignition temperature | 538°C |
| Explosive limits in air | 5.6–40.0 vol% |
| RTECS number | MW6825000 |
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | Hydrogen fluoride |
| Other cations | Sodium cyanide Potassium cyanide |
| Related compounds | Cyanogen Cyanogen chloride |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references | |
Hydrogen cyanide is a chemical compound with chemical formula H-C≡N. A solution of hydrogen cyanide in water is called hydrocyanic acid or prussic acid. Pure hydrogen cyanide is a colorless, very poisonous, and highly volatile liquid that boils slightly above room temperature at 26 °C, thereby generating hydrogen cyanide gas. Hydrogen cyanide has a faint, bitter, almond-like odor that some people are unable to smell due to a genetic trait. Hydrogen cyanide is weakly acidic and partly converts to the cyanide ion CN– in aqueous solution, resulting in a colorless volatile liquid with the typical hydrogen cyanide odor. The salts of hydrogen cyanide are known as cyanides.
Hydrogen cyanide is produced in large quantities all over the world by the chemical industry where it is used in tempering steel, dyeing, explosives, engraving, the production of acrylic resin plastic, and other organic chemical products. Its use in insect killing jars has now largely been replaced by less toxic ethyl acetate. It can be produced by reacting a cyanide salt with a strong acid, or directly from ammonia and carbon monoxide.
Fruits that have a pit, such as cherries or apricots, often contain small quantities of hydrogen cyanide in the pit. Bitter almonds, from which almond oil and flavoring is made, also contain hydrogen cyanide. Some millipedes release hydrogen cyanide as a defense mechanism. Hydrogen cyanide is contained in the exhaust of vehicles, in tobacco smoke, and in the smoke of burning nitrogen-containing plastics.
An HCN concentration of 300 parts per million of air will kill a human within a few minutes. The toxicity is caused by the cyanide ion. The mechanism of this toxicity, and the uses of the poison, are described on the cyanide page. Hydrogen cyanide (under the brand name Zyklon B) was perhaps most infamously employed by the Nazi regime in Germany as a method of mass-execution. Hydrogen cyanide is now listed under schedule 3 of the Chemical Weapons Convention.
Hydrogen cyanide forms a foul tasting compound when it combines with tobacco smoke. For this reason, some chemists choose to have a lit cigarette in their mouth while they are working with it, as they receive an early warning against possible cyanide poisoning.
Hydrogen cyanide gas in air is explosive at concentrations over 56,000 ppm.
Reactions
- hydrogen cyanide + ketone or aldehyde → cyanohydrin
External links
- International Chemical Safety Card 0492 (http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc04/icsc0492.htm)
- NIOSH Pocket Guide to Chemical Hazards (http://www.cdc.gov/niosh/npg/npgd0333.html)
- NIST Standard Reference Database (http://webbook.nist.gov/chemistry/)
- European Chemicals Bureau (http://ecb.jrc.it/)
- CSST (Canada) (http://www.reptox.csst.qc.ca/Produit.asp?no_produit=554&nom=Hydrogen+cyanide)
- OSHA: HCN Health Guidelines (http://www.osha.gov/SLTC/healthguidelines/hydrogencyanide/recognition.html)de:Cyanwasserstoff
es:Cianuro de hidrógeno fr:Cyanure d'hydrogène nl:Blauwzuur ja:シアン化水素 pl:Cyjanowodór pt:Ácido cianídrico ru:Синильная кислота sv:Vätecyanid