Editing Hydrogen cyanide (section)

==Occurrence==
HCN is obtainable from [[fruit]]s that have a [[endocarp|pit]], such as [[cherry|cherries]], [[apricot]]s, [[apple]]s, and nuts such as [[bitter almonds]], from which almond oil and extract is made. Many of these pits contain small amounts of [[cyanohydrin]]s such as [[mandelonitrile]] and [[amygdalin]], which slowly release hydrogen cyanide.<ref>{{cite journal | vauthors = Vetter J | title = Plant cyanogenic glycosides | journal = Toxicon | volume = 38 | issue = 1 | pages = 11–36 | date = January 2000 | pmid = 10669009 | doi = 10.1016/S0041-0101(99)00128-2| bibcode = 2000Txcn...38...11V }}</ref><ref>{{cite journal | vauthors = Jones DA | title = Why are so many food plants cyanogenic? | journal = Phytochemistry | volume = 47 | issue = 2 | pages = 155–162 | date = January 1998 | pmid = 9431670 | doi = 10.1016/S0031-9422(97)00425-1 | bibcode = 1998PChem..47..155J }}</ref> One hundred grams of crushed apple seeds can yield about 70&nbsp;mg of HCN.<ref>{{cite web |url=http://www.thenakedscientists.com/HTML/index.php?id=31&tx_naksciquestions_pi1%5BshowUid%5D=2737&cHash=69220df3a3 |title=Are Apple Cores Poisonous? |access-date=6 March 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140306130316/http://www.thenakedscientists.com/HTML/index.php?id=31&tx_naksciquestions_pi1%5BshowUid%5D=2737&cHash=69220df3a3 |publisher=The Naked Scientists|date=26 September 2010|archive-date=6 March 2014 }}</ref>  The roots of [[cassava]] plants contain [[cyanogenic glycosides]] such as [[linamarin]], which decompose into HCN in yields of up to 370&nbsp;mg per kilogram of fresh root.<ref>{{cite journal | vauthors = Aregheore EM, Agunbiade OO | title = The toxic effects of cassava (manihot esculenta grantz) diets on humans: a review | journal = Veterinary and Human Toxicology | volume = 33 | issue = 3 | pages = 274–275 | date = June 1991 | pmid = 1650055 }}</ref> Some [[millipede]]s, such as ''[[Harpaphe haydeniana]]'', ''[[Desmoxytes purpurosea]]'', and ''[[Apheloria]]'' release hydrogen cyanide as a defense mechanism,<ref>{{cite journal | vauthors = Blum MS, Woodring JP | title = Secretion of Benzaldehyde and Hydrogen Cyanide by the Millipede Pachydesmus crassicutis (Wood) | journal = Science | volume = 138 | issue = 3539 | pages = 512–513 | date = October 1962 | pmid = 17753947 | doi = 10.1126/science.138.3539.512 | s2cid = 40193390 | bibcode = 1962Sci...138..512B }}</ref> as do certain insects, such as [[Zygaenidae|burnet moths]] and the larvae of ''[[Paropsisterna|Paropsisterna eucalyptus]]''.<ref>{{cite journal | vauthors = Zagrobelny M, de Castro ÉC, Møller BL, Bak S | title = Cyanogenesis in Arthropods: From Chemical Warfare to Nuptial Gifts | journal = Insects | volume = 9 | issue = 2 | pages = 51 | date = May 2018 | pmid = 29751568 | pmc = 6023451 | doi = 10.3390/insects9020051 | doi-access = free }}</ref> Hydrogen cyanide is contained in the exhaust of vehicles, and in smoke from burning nitrogen-containing [[plastic]]s.[[File:PIA18431-SaturnMoon-Titan-SouthPoleVortex-Cloud-20121129.jpg|thumb|left|The South Pole Vortex of Saturn's moon [[Titan (moon)|Titan]] is a giant swirling cloud of HCN (November 29, 2012)]]

=== On Titan ===
HCN has been measured in [[Atmosphere of Titan|Titan's atmosphere]] by four instruments on the [[Cassini–Huygens|Cassini space probe]], one instrument on [[Voyager 1|Voyager]], and one instrument on Earth.<ref>{{Cite journal| vauthors = Loison JC, Hébrard E, Dobrijevic M, Hickson KM, Caralp F, Hue V, Gronoff G, Venot O, Bénilan Y | display-authors = 6 |date=February 2015|title=The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan|journal=Icarus|volume=247|pages=218–247|doi=10.1016/j.icarus.2014.09.039|bibcode=2015Icar..247..218L|url=https://lirias.kuleuven.be/handle/123456789/486735}}</ref> One of these measurements was ''in situ'', where the Cassini spacecraft dipped between {{cvt|1000 and 1100|km}} above Titan's surface to collect atmospheric gas for [[mass spectrometry]] analysis.<ref>{{Cite journal| vauthors = Magee BA, Waite JH, Mandt KE, Westlake J, Bell J, Gell DA |date=December 2009|title=INMS-derived composition of Titan's upper atmosphere: Analysis methods and model comparison|journal=Planetary and Space Science|volume=57|issue=14–15|pages=1895–1916|doi=10.1016/j.pss.2009.06.016|bibcode=2009P&SS...57.1895M}}</ref> HCN initially forms in Titan's atmosphere through the reaction of photochemically produced methane and nitrogen radicals which proceed through the H<sub>2</sub>CN intermediate, e.g., (CH<sub>3</sub> + N → H<sub>2</sub>CN + H → HCN + H<sub>2</sub>).<ref name="pearce2020">{{cite journal | vauthors = Pearce BK, Molaverdikhani K, Pudritz RE, Henning T, Hébrard E |title=HCN Production in Titan's Atmosphere: Coupling Quantum Chemistry and Disequilibrium Atmospheric Modeling |journal=Astrophysical Journal |year=2020 |volume=901 |issue=2 |page=110 |doi=10.3847/1538-4357/abae5c |arxiv=2008.04312 |bibcode=2020ApJ...901..110P |s2cid=221095540 |doi-access=free }}</ref><ref>{{cite journal | vauthors = Pearce BK, Ayers PW, Pudritz RE | title = A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients | journal = The Journal of Physical Chemistry A | volume = 123 | issue = 9 | pages = 1861–1873 | date = March 2019 | pmid = 30721064 | doi = 10.1021/acs.jpca.8b11323 | arxiv = 1902.05574 | s2cid = 73442008 | bibcode = 2019JPCA..123.1861P }}</ref> Ultraviolet radiation breaks HCN up into CN + H; however, CN is efficiently recycled back into HCN via the reaction CN + CH<sub>4</sub> → HCN + CH<sub>3</sub>.<ref name="pearce2020" />

=== On the young Earth ===
It has been postulated that carbon from a cascade of asteroids (known as the [[Late Heavy Bombardment]]), resulting from interaction of Jupiter and Saturn, blasted the surface of young Earth and reacted with nitrogen in Earth's atmosphere to form HCN.<ref>{{cite news |url=https://www.nytimes.com/2015/05/05/science/making-sense-of-the-chemistry-that-led-to-life-on-earth.html |title=Making Sense of the Chemistry That Led to Life on Earth |access-date=5 May 2015 |newspaper=The New York Times |date=2015-05-04 | vauthors = Wade N }}</ref>

=== In mammals ===
Some authors{{who|date=December 2020}} have shown that [[neuron]]s can produce hydrogen cyanide upon activation of their [[opioid]] [[receptor (biochemistry)|receptors]] by endogenous or exogenous opioids. They have also shown that neuronal production of HCN activates [[NMDA receptor]]s and plays a role in [[signal transduction]] between neuronal cells ([[neurotransmission]]). Moreover, increased endogenous neuronal HCN production under opioids was seemingly needed for adequate opioid [[analgesia]], as analgesic action of opioids was attenuated by HCN scavengers. They considered endogenous HCN to be a [[neuromodulator]].<ref name="pmid9369328">{{cite journal | vauthors = Borowitz JL, Gunasekar PG, Isom GE | title = Hydrogen cyanide generation by mu-opiate receptor activation: possible neuromodulatory role of endogenous cyanide | journal = Brain Research | volume = 768 | issue = 1–2 | pages = 294–300 | date = September 1997 | pmid = 9369328 | doi = 10.1016/S0006-8993(97)00659-8 | s2cid = 12277593}}</ref>

It has also been shown that, while stimulating [[muscarinic]] [[cholinergic]] receptors in cultured [[pheochromocytoma]] cells ''increases'' HCN production, in a living organism (''in vivo'') muscarinic cholinergic stimulation actually ''decreases'' HCN production.<ref>{{cite journal | vauthors = Gunasekar PG, Prabhakaran K, Li L, Zhang L, Isom GE, Borowitz JL | title = Receptor mechanisms mediating cyanide generation in PC12 cells and rat brain | journal = Neuroscience Research | volume = 49 | issue = 1 | pages = 13–18 | date = May 2004 | pmid = 15099699 | doi = 10.1016/j.neures.2004.01.006 | s2cid = 29850349}}</ref>

[[Leukocyte]]s generate HCN during [[phagocytosis]], and can kill [[bacteria]], [[fungi]], and other pathogens by generating several different toxic chemicals, one of which is hydrogen cyanide.<ref name="pmid9369328" />

The [[vasodilatation]] caused by [[sodium nitroprusside]] has been shown to be mediated not only by NO generation, but also by endogenous cyanide generation, which adds not only toxicity, but also some additional antihypertensive efficacy compared to [[nitroglycerine]] and other non-cyanogenic nitrates which do not cause blood cyanide levels to rise.<ref>{{cite journal | vauthors = Smith RP, Kruszyna H | title = Toxicology of some inorganic antihypertensive anions | journal = Federation Proceedings | volume = 35 | issue = 1 | pages = 69–72 | date = January 1976 | pmid = 1245233 }}</ref>

HCN is a constituent of [[tobacco smoke]].<ref>{{cite journal | vauthors = Talhout R, Schulz T, Florek E, van Benthem J, Wester P, Opperhuizen A | title = Hazardous compounds in tobacco smoke | journal = International Journal of Environmental Research and Public Health | volume = 8 | issue = 2 | pages = 613–628 | date = February 2011 | pmid = 21556207 | pmc = 3084482 | doi = 10.3390/ijerph8020613 | doi-access = free}}</ref>

===HCN and the origin of life===
As a precursor to amino acids and nucleic acids, hydrogen cyanide has been proposed to have played a part in the [[Abiogenesis|origin of life]]. Compounds of special interest are [[oligomer]]s of HCN including its trimer [[aminomalononitrile]] and tetramer [[diaminomaleonitrile]], which can be described as (HCN)3 and (HCN)4, respectively.<ref>{{cite journal |doi=10.3390/life3030421|doi-access=free|title=Simple Organics and Biomonomers Identified in HCN Polymers: An Overview|year=2013|last1=Ruiz-Bermejo|first1=Marta|last2=Zorzano|first2=María-Paz|last3=Osuna-Esteban|first3=Susana|journal=Life|volume=3|issue=3|pages=421–448|pmid=25369814|pmc=4187177|bibcode=2013Life....3..421R }}</ref> Although the relationship of these chemical reactions to the origin of life theory remains speculative, studies in this area uncovered new pathways to organic compounds derived from the condensation of HCN (e.g. [[Adenine]]).<ref>{{cite journal | vauthors = Al-Azmi A, Elassar AZ, Booth BL | title = The Chemistry of Diaminomaleonitrile and its Utility in Heterocyclic Synthesis | journal = Tetrahedron | year = 2003 | volume = 59 | issue = 16 | pages = 2749–2763 | doi = 10.1016/S0040-4020(03)00153-4}}</ref>

===In space===
{{see also|Astrochemistry}}
Because hydrogen cyanide is a precursor to nucleic acids, which are critical for terrestrial life, [[astronomers]] are incentivized to search for derivatives of HCN. <ref>{{Cite AV media |url=https://www.ted.com/talks/karin_oberg_the_galactic_recipe_for_a_living_planet/transcript?subtitle=en |title=The galactic recipe for a living planet |date=2020-04-10 |last=Öberg |first=Karin |language=en |access-date=2024-12-24 |via=www.ted.com}}</ref>

HCN has been detected in the [[interstellar medium]]<ref name="Snyder, Lewis E.; Buhl, David 1971 L47">{{cite journal | title = Observations of Radio Emission from Interstellar Hydrogen Cyanide | vauthors = Snyder LE, Buhl D | journal = Astrophysical Journal | year = 1971 | volume = 163 | pages = L47–L52 | doi = 10.1086/180664 | bibcode=1971ApJ...163L..47S}}</ref> and in the atmospheres of [[carbon star]]s.<ref>{{cite book | vauthors = Jørgensen UG | title=Molecules in Astrophysics: Probes and Processes | chapter=Cool Star Models | volume=178 | series=International Astronomical Union Symposia. Molecules in Astrophysics: Probes and Processes | veditors = van Dishoeck EF | publisher=Springer Science & Business Media | year=1997 | isbn=978-0792345381 | page=446 | chapter-url=https://books.google.com/books?id=VW50otz5v8sC&pg=PA446 }}</ref> Since then, extensive studies have probed formation and destruction pathways of HCN in various environments and examined its use as a tracer for a variety of astronomical species and processes. HCN can be [[Observation|observed]] from ground-based [[telescope]]s through a number of [[Atmosphere|atmospheric]] windows.<ref>{{cite journal | vauthors = Treffers RR, Larson HP, Fink U, Gautier TN | title = Upper limits to trace constituents in Jupiter's atmosphere from an analysis of its 5-μm spectrum | journal = Icarus | year = 1978 | volume = 34 | issue = 2 | pages = 331–343 | doi = 10.1016/0019-1035(78)90171-9 | bibcode = 1978Icar...34..331T }}</ref> The J=1→0, J=3→2, J= 4→3, and J=10→9 pure [[rotational transition]]s have all been observed.<ref name="Snyder, Lewis E.; Buhl, David 1971 L47" /><ref>{{cite journal | vauthors = Bieging JH, Shaked S, Gensheimer PD | title = Submillimeter- and Millimeter-Wavelength Observations of SiO and HCN in Circumstellar Envelopes of AGB Stars | journal = Astrophysical Journal | year = 2000 | volume = 543 | issue = 2 | pages = 897–921 | doi = 10.1086/317129 | bibcode = 2000ApJ...543..897B | doi-access = free}}</ref><ref>{{cite journal | title = Detection of a Second, Strong Sub-millimeter HCN Laser Line toward Carbon Stars | vauthors = Schilke P, Menten KM | journal = Astrophysical Journal | year = 2003 | volume = 583 | issue = 1 | pages = 446–450 | doi = 10.1086/345099 | bibcode = 2003ApJ...583..446S | s2cid = 122549795| doi-access = free }}</ref>

HCN is formed in [[Interstellar medium|interstellar]] clouds through one of two major pathways:<ref name="Boger, G. I. and Sternberg, A. 2005 302">{{cite journal | title = CN and HCN in Dense Interstellar Clouds | vauthors = Boger GI, Sternberg A | journal = Astrophysical Journal | year = 2005 | volume = 632 | issue = 1 | pages = 302–315 | doi = 10.1086/432864 | bibcode = 2005ApJ...632..302B | arxiv = astro-ph/0506535 |s2cid=118958200 }}</ref> via a neutral-neutral reaction (CH<sub>2</sub> + N → HCN + H) and via [[dissociative recombination]] (HCNH<sup>+</sup> + e<sup>−</sup> → HCN + H). The dissociative recombination pathway is dominant by 30%; however, the [[HCNH+|HCNH<sup>+</sup>]] must be in its linear form. Dissociative recombination with its structural isomer, H<sub>2</sub>NC<sup>+</sup>, exclusively produces [[hydrogen isocyanide]] (HNC).

HCN is destroyed in interstellar clouds through a number of mechanisms depending on the location in the cloud.<ref name="Boger, G. I. and Sternberg, A. 2005 302" /> In [[photon-dominated region]]s (PDRs), photodissociation dominates, producing [[Cyanide|CN]] (HCN + ν → CN + H). At further depths, photodissociation by cosmic rays dominate, producing CN (HCN + cr → CN + H). In the dark core, two competing mechanisms destroy it, forming HCN<sup>+</sup> and HCNH<sup>+</sup> (HCN + H<sup>+</sup> → HCN<sup>+</sup> + H; HCN + HCO<sup>+</sup> → HCNH<sup>+</sup> + CO). The reaction with HCO<sup>+</sup> dominates by a factor of ~3.5. HCN has been used to analyze a variety of species and processes in the interstellar medium. It has been suggested as a tracer for dense molecular gas<ref>{{cite journal | vauthors = Gao Y, Solomon PM | title = The Star Formation Rate and Dense Molecular Gas in Galaxies | journal = Astrophysical Journal | year = 2004 | volume = 606 | issue = 1 | pages = 271–290 | doi = 10.1086/382999 | bibcode=2004ApJ...606..271G | arxiv = astro-ph/0310339 |s2cid=11335358 }}</ref><ref>{{cite journal | vauthors = Gao Y, olomon PM | title = HCN Survey of Normal Spiral, Infrared-luminous, and Ultraluminous Galaxies | journal = Astrophysical Journal Supplement Series | year = 2004 | volume = 152 |issue=1 | pages = 63–80 | doi = 10.1086/383003 | bibcode = 2004ApJS..152...63G | arxiv = astro-ph/0310341 |s2cid=9135663 }}</ref> and as a tracer of stellar inflow in high-mass star-forming regions.<ref>{{cite journal | vauthors = Wu J, Evans NJ | title = Indications of Inflow Motions in Regions Forming Massive Stars | journal = Astrophysical Journal | year = 2003 | volume = 592 | issue = 2 | pages = L79–L82 | doi = 10.1086/377679 | bibcode = 2003ApJ...592L..79W | arxiv = astro-ph/0306543 |s2cid=8016228 }}</ref> Further, the HNC/HCN ratio has been shown to be an excellent method for distinguishing between PDRs and X-ray-dominated regions (XDRs).<ref>{{cite journal | vauthors = Loenen AF | journal = Proceedings IAU Symposium | year = 2007 | title = Molecular properties of (U)LIRGs: CO, HCN, HNC and HCO<sup>+</sup> | volume = 242 | pages = 462–466 |bibcode=2007IAUS..242..462L| doi = 10.1017/S1743921307013609 | arxiv = 0709.3423 | s2cid = 14398456}}</ref>

On 11 August 2014, astronomers released studies, using the [[Atacama Large Millimeter Array|Atacama Large Millimeter/Submillimeter Array (ALMA)]] for the first time, that detailed the distribution of HCN, [[Hydrogen isocyanide|HNC]], [[Formaldehyde|H<sub>2</sub>CO]], and [[dust]] inside the [[Coma (cometary)|comae]] of [[comet]]s [[C/2012 F6 (Lemmon)]] and [[Comet ISON|C/2012 S1 (ISON)]].<ref>{{cite web | vauthors = Zubritsky E, Neal-Jones N |title=Release 14-038 – NASA's 3-D Study of Comets Reveals Chemical Factory at Work |url=http://www.nasa.gov/press/2014/august/goddard/nasa-s-3-d-study-of-comets-reveals-chemical-factory-at-work |date=11 August 2014 |work=[[NASA]] |access-date=12 August 2014 }}</ref><ref>{{cite journal | vauthors = Cordiner MA, Remijan AJ, Boissier J, Milam SN, Mumma MJ, Charnley SB, Paganini L, Villanueva G, Bockelée-Morvan D, Kuan YJ, Chuang YL | display-authors = 6 |title=Mapping the Release of Volatiles in the Inner Comae of Comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) Using the Atacama Large Millimeter/Submillimeter Array |date=11 August 2014 |journal=[[The Astrophysical Journal]] |volume=792 |pages=L2 |issue=1 |doi=10.1088/2041-8205/792/1/L2 |bibcode= 2014ApJ...792L...2C |arxiv=1408.2458|s2cid=26277035 }}</ref>

In February 2016, it was announced that traces of hydrogen cyanide were found in the atmosphere of the hot [[Super-Earth]] [[55 Cancri e]] with NASA's [[Hubble Space Telescope]].<ref>{{cite web|url=https://phys.org/news/2016-02-super-earth-atmosphere.html|title=First detection of super-earth atmosphere|publisher=ESA/Hubble Information Centre|date=February 16, 2016}}</ref>

On 14 December 2023, astronomers reported the first time discovery, in the [[Plume (fluid dynamics)|plume]]s of [[Enceladus]], moon of the planet [[Saturn]], of hydrogen cyanide, a possible chemical essential for [[life]]<ref>{{cite news |last=Green |first=Jaime |title=What Is Life? - The answer matters in space exploration. But we still don't really know. |url=https://www.theatlantic.com/science/archive/2023/12/defining-life-existentialism-scientific-theory/676238/ |date=5 December 2023 |work=[[The Atlantic]] |url-status=live |archiveurl=https://archive.today/20231205121742/https://www.theatlantic.com/science/archive/2023/12/defining-life-existentialism-scientific-theory/676238/ |archivedate=5 December 2023 |accessdate=15 December 2023 }}</ref> as we know it, as well as other [[organic molecule]]s, some of which are yet to be better identified and understood. According to the researchers, "these [newly discovered] compounds could potentially support extant [[Microorganism|microbial communities]] or drive complex [[organic synthesis]] leading to the [[origin of life]]."<ref>{{cite news |last=Chang |first=Kenneth |title=Poison Gas Hints at Potential for Life on an Ocean Moon of Saturn - A researcher who has studied the icy world said "the prospects for the development of life are getting better and better on Enceladus." |url=https://www.nytimes.com/2023/12/14/science/enceladus-moon-cyanide-life-saturn.html |date=14 December 2023 |work=[[The New York Times]] |url-status=live |archiveurl=https://archive.today/20231214210144/https://www.nytimes.com/2023/12/14/science/enceladus-moon-cyanide-life-saturn.html |archivedate=14 December 2023 |accessdate=15 December 2023 }}</ref><ref>{{cite journal |author=Peter, Jonah S. |display-authors=et al. |title=Detection of HCN and diverse redox chemistry in the plume of Enceladus |url=https://www.nature.com/articles/s41550-023-02160-0 |date=14 December 2023 |journal=[[Nature Astronomy]] |volume=8 |issue=2 |pages=164–173 |doi=10.1038/s41550-023-02160-0 |arxiv=2301.05259 |bibcode=2024NatAs...8..164P |s2cid=255825649 |url-status=live |archiveurl=https://archive.today/20231215144349/https://www.nature.com/articles/s41550-023-02160-0 |archivedate=15 December 2023 |accessdate=15 December 2023 }}</ref>