Difference between revisions of "Hydrogen cyanide" - New World Encyclopedia
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| − | '''Hydrogen cyanide''' is a [[chemical compound]] with [[chemical formula]] HCN. | + | |
| + | '''Hydrogen cyanide''' is a [[chemical compound]] with the [[chemical formula|formula]] HCN. It is a [[color]]less, very [[poison]]ous, and highly [[volatility (chemistry)|volatile]] liquid that [[boiling|boils]] slightly above [[room temperature]]. The gas is explosive in air, at concentrations above 5.6 percent. A [[solution]] of hydrogen cyanide in [[water (molecule)|water]] is called '''hydrocyanic acid''', and its [[salt]]s are called '''[[cyanide]]s'''. | ||
| + | |||
| + | Despite its toxicity, HCN is a highly valuable precursor for the synthesis of many chemical compounds, ranging from polymers to pharmaceuticals. In the year 2000, an estimated 1,615 million pounds (732,552 tons) of this substance was produced in the United States.<ref>[http://www.the-innovation-group.com/ChemProfiles/Hydrogen%20Cyanide.htm Hydrogen Cyanide.] Retrieved December 12, 2007.</ref> | ||
==Occurrence == | ==Occurrence == | ||
| Line 51: | Line 54: | ||
Hydrogen cyanide is contained in the exhaust of vehicles, in [[tobacco]] and wood smoke, and in smoke from burning nitrogen-containing [[plastic]]s. | Hydrogen cyanide is contained in the exhaust of vehicles, in [[tobacco]] and wood smoke, and in smoke from burning nitrogen-containing [[plastic]]s. | ||
| − | == | + | ==Role in the origin of life?== |
Some have proposed that hydrogen cyanide may have played a part in the [[origin of life]], in terms of being a possible precursor to amino acids and nucleic acids. [[Leslie Orgel]], among other researchers, has written extensively on the condensation reactions of HCN. Although the relationship of these chemical reactions to the origin of life remains speculative, studies in this area have led to discoveries of new pathways to organic compounds derived from the condensation of HCN.<ref>Al-Azmi, A., A.Z. Elassar, B.L. Booth. 2003. The Chemistry of Diaminomaleonitrile and its Utility in Heterocyclic Synthesis. ''Tetrahedron''. 59:2749-2763.</ref> | Some have proposed that hydrogen cyanide may have played a part in the [[origin of life]], in terms of being a possible precursor to amino acids and nucleic acids. [[Leslie Orgel]], among other researchers, has written extensively on the condensation reactions of HCN. Although the relationship of these chemical reactions to the origin of life remains speculative, studies in this area have led to discoveries of new pathways to organic compounds derived from the condensation of HCN.<ref>Al-Azmi, A., A.Z. Elassar, B.L. Booth. 2003. The Chemistry of Diaminomaleonitrile and its Utility in Heterocyclic Synthesis. ''Tetrahedron''. 59:2749-2763.</ref> | ||
| − | == | + | == Properties == |
| − | Currently hydrogen cyanide is produced in large quantities by three processes. The most important | + | Hydrogen cyanide has a faint, bitter, [[almond]]-like [[odor]]. Some people, however, are unable to [[olfactory system|detect]] the odor due to a [[gene]]tic [[Trait (biological)|trait]].<ref>[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=304300 Cyanide, inability to smell]. Online Mendelian Inheritance in Man. Retrieved December 8, 2007.</ref> |
| + | |||
| + | The boiling point of HCN is 26 [[Celsius|°C]] (78.8 [[Fahrenheit|°F]]). In air, HCN gas is explosive at concentrations over 5.6 percent, equivalent to 56,000 [[parts per million]] (ppm)<ref name=http://www.cdc.gov/Niosh/idlh/74908.html>[http://www.cdc.gov/Niosh/idlh/74908.html Hydrogen cyanide.] Centers for Disease Control and Prevention. Retrieved December 8, 2007.</ref>. | ||
| + | |||
| + | Hydrogen cyanide is weakly [[acid]]ic and partly [[ionization|ionizes]] in solution to give the [[cyanide|cyanide anion]], CN<sup>–</sup>. | ||
| + | |||
| + | ==Production == | ||
| + | |||
| + | Currently, hydrogen cyanide is produced in large quantities by three processes. The most important of these processes is called [[Andrussov oxidation]], invented by [[Leonid Andrussow]]. In this method, [[methane]] and [[ammonia]] react in the presence of [[oxygen]] at about 1200 °C over a [[platinum]] catalyst:<ref>Andrussow, L. 1935. The catalytic oxydation of ammonia-methane-mixtures to hydrogen cyanide. ''Angewandte Chemie''. 48:593-595.</ref> | ||
::CH<sub>4</sub> + NH<sub>3</sub> + 1.5O<sub>2</sub> → HCN + 3H<sub>2</sub>O | ::CH<sub>4</sub> + NH<sub>3</sub> + 1.5O<sub>2</sub> → HCN + 3H<sub>2</sub>O | ||
The energy needed for the reaction is provided by the part oxidation of methane and ammonia. | The energy needed for the reaction is provided by the part oxidation of methane and ammonia. | ||
| − | Of lesser importance is the [[Degussa]] process (BMA process) in which no oxygen is added and | + | Of lesser importance is the [[Degussa]] process (BMA process), in which no oxygen is added and energy is transferred indirectly through the reactor wall:<ref>Endter, F. 1958. Die technische Synthese von Cyanwasserstoff aus Methan und Ammoniak ohne Zusatz von Sauerstoff. ''Chemie Ingenieur Technik''. 30:5:281-376.</ref> |
::CH<sub>4</sub> + NH<sub>3</sub> → HCN + 3H<sub>2</sub> | ::CH<sub>4</sub> + NH<sub>3</sub> → HCN + 3H<sub>2</sub> | ||
| + | This reaction is akin to [[steam reforming]], the reaction of [[methane]] and water. | ||
| − | + | In another process (practiced at [[BASF]]), [[formamide]] is heated and split into hydrogen cyanide and water: | |
| − | In another process | ||
::CH(O)NH<sub>2</sub> → HCN + H<sub>2</sub>O | ::CH(O)NH<sub>2</sub> → HCN + H<sub>2</sub>O | ||
In the laboratory, small amounts of HCN are produced by the addition of acids to cyanide salts of alkali metals: | In the laboratory, small amounts of HCN are produced by the addition of acids to cyanide salts of alkali metals: | ||
::H<sup>+</sup> + NaCN → HCN + Na<sup>+</sup> | ::H<sup>+</sup> + NaCN → HCN + Na<sup>+</sup> | ||
| − | This reaction | + | This reaction has sometimes been the basis of accidental poisonings because the acid converts a nonvolatile cyanide salt into the gaseous HCN. |
==Reactions== | ==Reactions== | ||
| − | HCN | + | HCN combines with [[ketone]]s and [[aldehyde]]s to give [[cyanohydrin]]s. Amino acids are prepared by this reaction. For instance, the essential [[amino acid]] [[methionine]] is manufactured by this route. The cyanohydrin of [[acetone]] is a precursor to [[methyl methacrylate]]. |
| − | In [[hydrocyanation]], HCN adds to [[alkene]]s to give nitriles. | + | In a reaction known as [[hydrocyanation]], HCN adds to [[alkene]]s to give nitriles. This reaction is employed to manufacture [[adiponitrile]], the precursor to [[Nylon|Nylon 66]]. |
== Applications == | == Applications == | ||
| − | + | Hydrogen cyanide is a valuable starting material for the synthesis of various [[organic compound]]s. Its main use is in the production of adiponitrile, which is then used to manufacture nylon. A second important application is for the synthesis of methyl methacrylate, which in turn is needed for the production of [[polymethyl methacrylate]] (PMMA) resins. In addition, HCN is used in [[tempering]] [[steel]], [[dye]]ing, [[explosive]]s, and [[engraving]]. | |
| + | |||
| + | The less toxic [[ethyl acetate]] (C<sub>4</sub>H<sub>8</sub>O<sub>2</sub>) has now largely replaced the use of cyanide in [[insect]] [[killing jar]]s. However, cyanide is being used for [[capital punishment]]. | ||
===As a chemical weapon=== | ===As a chemical weapon=== | ||
| − | An HCN concentration of 300 parts per million in air will kill a [[homo sapiens|human]] within a few minutes.<ref>[http://www.osha.gov/SLTC/healthguidelines/hydrogencyanide/recognition.html Occupational Safety and Health Guideline for Hydrogen Cyanide.] OSHA. Retrieved December 8, 2007.</ref> The toxicity is caused by the [[cyanide]] ion, which prevents [[cellular respiration]] | + | An HCN concentration of 300 parts per million in air will kill a [[homo sapiens|human]] within a few minutes.<ref>[http://www.osha.gov/SLTC/healthguidelines/hydrogencyanide/recognition.html Occupational Safety and Health Guideline for Hydrogen Cyanide.] OSHA. Retrieved December 8, 2007.</ref> The toxicity is caused by the [[cyanide]] ion, which prevents [[cellular respiration]]. |
| − | + | [[Zyklon B]] was an insecticide that releases gaseous hydrogen cyanide upon exposure to air. It gained notoriety for its use by the [[Nazi Germany|Nazi]] regime in the mid-twentieth century as a method of mass murder, in the [[gas chamber]]s of [[Auschwitz]] and [[Majdanek]] during [[the Holocaust]]. | |
| − | + | Hydrogen cyanide is commonly listed amongst [[chemical warfare agent]]s that cause general poisoning.<ref>[http://www.opcw.org/resp/html/hcn.html Hydrogen Cyanide]. Organization for the Prohibition of Chemical Weapons. Retrieved December 8, 2007.</ref> It is listed under [[List of Schedule 3 substances (CWC)|Schedule 3]] of the [[Chemical Weapons Convention]] as a potential weapon with large-scale industrial uses. As such, manufacturing plants in signatory countries that produce more than 30 tonnes per year must be declared to, and can be inspected by, the [[Organization for the Prohibition of Chemical Weapons]] (OPCW). | |
| − | + | Although there have been no verified instances of this compound being used as a weapon in warfare, it has been reported that hydrogen cyanide may have been employed by [[Iraq]] in the war against [[Iran]] and against the [[Kurd]]s in northern Iraq during the 1980s<ref name=http://www.bt.cdc.gov/agent/cyanide/basics/facts.asp>[http://www.bt.cdc.gov/agent/cyanide/basics/facts.asp Facts About Cyanide]. Centers for Disease Control and Prevention. Retrieved December 8, 2007.</ref>. | |
| − | |||
| − | + | In 1995, a device was discovered in a restroom in the [[Kayabacho]] [[Tokyo]] subway station consisting of bags of [[sodium cyanide]] and [[sulfuric acid]] with a remote controlled motor to rupture them in what was believed to be an attempt to produce toxic amounts of hydrogen cyanide gas by the [[Aum Shinrikyo]] [[cult]].<ref>[http://cns.miis.edu/pubs/reports/pdfs/aum_chrn.pdf Chronology of Aum Shinrikyo's CBW Activities]. James Martin Center for Nonproliferation Studies. Retrieved December 8, 2007.</ref> In 2003, [[Al Qaeda]] reportedly planned to attack the [[New York City Subway]] using hydrogen cyanide gas but aborted the attack for unknown reasons.<ref name=http://www.time.com/time/magazine/article/0,9171,1205478,00.html>Suskind, Ron. 2006. [http://www.time.com/time/magazine/article/0,9171,1205478,00.html The Untold Story of al-Qaeda's Plot to Attack the Subway.] Time. Retrieved December 8, 2007.</ref> | |
==See also== | ==See also== | ||
* [[Chemical warfare]] | * [[Chemical warfare]] | ||
| − | * [[ | + | * [[Nylon]] |
==Notes== | ==Notes== | ||
Revision as of 18:54, 12 December 2007
| Hydrogen cyanide | |
|---|---|
| |
| |
| IUPAC name | Hydrogen cyanide |
| Other names | Hydrocyanic acid prussic acid, formonitrile formic anammonide carbon hydride nitride cyclon |
| Identifiers | |
| CAS number | [] |
| RTECS number | MW6825000 |
| Properties | |
| Molecular formula | HCN |
| Molar mass | 27.03 g/mol |
| Appearance | Colorless gas or pale blue highly volatile liquid |
| Density | 0.687 g/cm³, liquid. |
| Melting point |
-13.4°C (259.75 K, 7.88°F) |
| Boiling point |
26°C (299.15 K, 78.8°F) |
| Solubility in water | Completely miscible. |
| Acidity (pKa) | 9.2 - 9.3 |
| Structure | |
| Molecular shape | Linear |
| Dipole moment | 2.98 D |
| Hazards | |
| Main hazards | Highly toxic, highly flammable. |
| NFPA 704 |
4
4
2
|
| R-phrases | R12, R26, R27, R28, R32. |
| S-phrases | (S1), S2, S7, S9, S13, S16, S28, S29, S45. |
| Flash point | −17.78 °C |
| Related Compounds | |
| Related compounds | Cyanogen Cyanogen chloride trimethylsilyl cyanide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Hydrogen cyanide is a chemical compound with the formula HCN. It is a colorless, very poisonous, and highly volatile liquid that boils slightly above room temperature. The gas is explosive in air, at concentrations above 5.6 percent. A solution of hydrogen cyanide in water is called hydrocyanic acid, and its salts are called cyanides.
Despite its toxicity, HCN is a highly valuable precursor for the synthesis of many chemical compounds, ranging from polymers to pharmaceuticals. In the year 2000, an estimated 1,615 million pounds (732,552 tons) of this substance was produced in the United States.[1]
Occurrence
Some fruits that have a pit (such as cherries and apricots), bitter almonds, and apple seeds contain small amounts of cyanohydrins such as mandelonitrile (CAS#532-28-5). Such molecules slowly decompose to release hydrogen cyanide.[2][3]
Some millipedes release hydrogen cyanide as a defense mechanism.[4] So do certain insects, such as some burnet moths.
Hydrogen cyanide is contained in the exhaust of vehicles, in tobacco and wood smoke, and in smoke from burning nitrogen-containing plastics.
Role in the origin of life?
Some have proposed that hydrogen cyanide may have played a part in the origin of life, in terms of being a possible precursor to amino acids and nucleic acids. Leslie Orgel, among other researchers, has written extensively on the condensation reactions of HCN. Although the relationship of these chemical reactions to the origin of life remains speculative, studies in this area have led to discoveries of new pathways to organic compounds derived from the condensation of HCN.[5]
Properties
Hydrogen cyanide has a faint, bitter, almond-like odor. Some people, however, are unable to detect the odor due to a genetic trait.[6]
The boiling point of HCN is 26 °C (78.8 °F). In air, HCN gas is explosive at concentrations over 5.6 percent, equivalent to 56,000 parts per million (ppm)[7].
Hydrogen cyanide is weakly acidic and partly ionizes in solution to give the cyanide anion, CN–.
Production
Currently, hydrogen cyanide is produced in large quantities by three processes. The most important of these processes is called Andrussov oxidation, invented by Leonid Andrussow. In this method, methane and ammonia react in the presence of oxygen at about 1200 °C over a platinum catalyst:[8]
- CH4 + NH3 + 1.5O2 → HCN + 3H2O
The energy needed for the reaction is provided by the part oxidation of methane and ammonia.
Of lesser importance is the Degussa process (BMA process), in which no oxygen is added and energy is transferred indirectly through the reactor wall:[9]
- CH4 + NH3 → HCN + 3H2
This reaction is akin to steam reforming, the reaction of methane and water.
In another process (practiced at BASF), formamide is heated and split into hydrogen cyanide and water:
- CH(O)NH2 → HCN + H2O
In the laboratory, small amounts of HCN are produced by the addition of acids to cyanide salts of alkali metals:
- H+ + NaCN → HCN + Na+
This reaction has sometimes been the basis of accidental poisonings because the acid converts a nonvolatile cyanide salt into the gaseous HCN.
Reactions
HCN combines with ketones and aldehydes to give cyanohydrins. Amino acids are prepared by this reaction. For instance, the essential amino acid methionine is manufactured by this route. The cyanohydrin of acetone is a precursor to methyl methacrylate.
In a reaction known as hydrocyanation, HCN adds to alkenes to give nitriles. This reaction is employed to manufacture adiponitrile, the precursor to Nylon 66.
Applications
Hydrogen cyanide is a valuable starting material for the synthesis of various organic compounds. Its main use is in the production of adiponitrile, which is then used to manufacture nylon. A second important application is for the synthesis of methyl methacrylate, which in turn is needed for the production of polymethyl methacrylate (PMMA) resins. In addition, HCN is used in tempering steel, dyeing, explosives, and engraving.
The less toxic ethyl acetate (C4H8O2) has now largely replaced the use of cyanide in insect killing jars. However, cyanide is being used for capital punishment.
As a chemical weapon
An HCN concentration of 300 parts per million in air will kill a human within a few minutes.[10] The toxicity is caused by the cyanide ion, which prevents cellular respiration.
Zyklon B was an insecticide that releases gaseous hydrogen cyanide upon exposure to air. It gained notoriety for its use by the Nazi regime in the mid-twentieth century as a method of mass murder, in the gas chambers of Auschwitz and Majdanek during the Holocaust.
Hydrogen cyanide is commonly listed amongst chemical warfare agents that cause general poisoning.[11] It is listed under Schedule 3 of the Chemical Weapons Convention as a potential weapon with large-scale industrial uses. As such, manufacturing plants in signatory countries that produce more than 30 tonnes per year must be declared to, and can be inspected by, the Organization for the Prohibition of Chemical Weapons (OPCW).
Although there have been no verified instances of this compound being used as a weapon in warfare, it has been reported that hydrogen cyanide may have been employed by Iraq in the war against Iran and against the Kurds in northern Iraq during the 1980s[12].
In 1995, a device was discovered in a restroom in the Kayabacho Tokyo subway station consisting of bags of sodium cyanide and sulfuric acid with a remote controlled motor to rupture them in what was believed to be an attempt to produce toxic amounts of hydrogen cyanide gas by the Aum Shinrikyo cult.[13] In 2003, Al Qaeda reportedly planned to attack the New York City Subway using hydrogen cyanide gas but aborted the attack for unknown reasons.[14]
See also
Notes
- ↑ Hydrogen Cyanide. Retrieved December 12, 2007.
- ↑ Vetter, J. 2000. Plant cyanogenic glycosides. Toxicon. 38:11-36.
- ↑ Jones, D.A. 1998. Why are so many food plants cyanogenic? Phytochemistry. 47:155-162.
- ↑ Blum, M.S., J.P. Woodring. 1962. Secretion of Benzaldehyde and Hydrogen Cyanide by the Millipede Pachydesmus crassicutis (Wood). Science. 138:512-13.
- ↑ Al-Azmi, A., A.Z. Elassar, B.L. Booth. 2003. The Chemistry of Diaminomaleonitrile and its Utility in Heterocyclic Synthesis. Tetrahedron. 59:2749-2763.
- ↑ Cyanide, inability to smell. Online Mendelian Inheritance in Man. Retrieved December 8, 2007.
- ↑ Hydrogen cyanide. Centers for Disease Control and Prevention. Retrieved December 8, 2007.
- ↑ Andrussow, L. 1935. The catalytic oxydation of ammonia-methane-mixtures to hydrogen cyanide. Angewandte Chemie. 48:593-595.
- ↑ Endter, F. 1958. Die technische Synthese von Cyanwasserstoff aus Methan und Ammoniak ohne Zusatz von Sauerstoff. Chemie Ingenieur Technik. 30:5:281-376.
- ↑ Occupational Safety and Health Guideline for Hydrogen Cyanide. OSHA. Retrieved December 8, 2007.
- ↑ Hydrogen Cyanide. Organization for the Prohibition of Chemical Weapons. Retrieved December 8, 2007.
- ↑ Facts About Cyanide. Centers for Disease Control and Prevention. Retrieved December 8, 2007.
- ↑ Chronology of Aum Shinrikyo's CBW Activities. James Martin Center for Nonproliferation Studies. Retrieved December 8, 2007.
- ↑ Suskind, Ron. 2006. The Untold Story of al-Qaeda's Plot to Attack the Subway. Time. Retrieved December 8, 2007.
ReferencesISBN links support NWE through referral fees
- Brown Jr., Theodore L., H. Eugene LeMay, Bruce Edward Bursten, and Julia R. Burdge. 2002. Chemistry: The Central Science. 9th ed. Upper Saddle River, NJ: Prentice Hall. ISBN 0130669970.
- Chang, Raymond. 2006. Chemistry. 9th ed. New York, NY: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
- Cotton, F. Albert, and Geoffrey Wilkinson. 1980. Advanced Inorganic Chemistry. 4th ed. New York, NY: Wiley. ISBN 0-471-02775-8.
External links
- International Chemical Safety Card 0492. Retrieved December 8, 2007.
- Hydrogen cyanide and cyanides (CICAD 61). Retrieved December 8, 2007.
- National Pollutant Inventory - Cyanide compounds fact sheet. Retrieved December 8, 2007.
- NIOSH Pocket Guide to Chemical Hazards. Retrieved December 8, 2007.
- European Chemicals Bureau. Retrieved December 8, 2007.
- Department of health review. Retrieved December 8, 2007.
- OSHA: HCN Health Guidelines. Retrieved December 8, 2007.
 | ||
|---|---|---|
| Blood agents: | Cyanogen chloride (CK) – Hydrogen cyanide (AC) | |
| Blister agents: | Lewisite (L) – Sulfur mustard gas (HD, H, HT, HL, HQ) – Nitrogen mustard gas (HN1, HN2, HN3) | |
| Nerve agents: | G-Agents: Tabun (GA) – Sarin (GB) – Soman (GD) – Cyclosarin (GF) | V-Agents: VE – VG – VM – VX | |
| Pulmonary agents: | Chlorine – Chloropicrin (PS) – Phosgene (CG) – Diphosgene (DP) | |
| Incapacitating agents: | Agent 15 (BZ) – KOLOKOL-1 | |
| Riot control agents: | Pepper spray (OC) – CS gas – CN gas (mace) – CR gas | |
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