Acetylene

Acetylene was discovered in 1836 by Edmund Davy, who identified it as a "new carburet of hydrogen".Edmund Davy (August 1836) [https://books.google.com/books?id=grtZAAAAcAAJ&pg=RA1-PA62 "Notice of a new gaseous bicarburet of hydrogen"] {{Webarchive|url=https://web.archive.org/web/20160506050712/https://books.google.com/books?id=grtZAAAAcAAJ&pg=RA1-PA62 |date=6 May 2016}}, Report of the Sixth Meeting of the British Association for the Advancement of Science ..., 5: 62–63.{{cite book |title=Acetylene: Its Properties, Manufacture and Uses |last1=Miller |first1=S. A. |year=1965 |publisher=Academic Press Inc. |volume=1 |url=https://books.google.com/books?id=-u1GAQAAIAAJ |access-date=16 July 2021 |archive-date=15 April 2021 |archive-url=https://web.archive.org/web/20210415082551/https://books.google.com/books?id=-u1GAQAAIAAJ |url-status=live }} It was an accidental discovery while attempting to isolate potassium metal. By heating potassium carbonate with carbon at very high temperatures, he produced a residue of what is now known as potassium carbide, (K₂C₂), which reacted with water to release the new gas. It was rediscovered in 1860 by French chemist Marcellin Berthelot, who coined the name acétylène.Bertholet (1860) [http://gallica.bnf.fr/ark:/12148/bpt6k3007r/f817.image "Note sur une nouvelle série de composés organiques, le quadricarbure d'hydrogène et ses dérivés"] {{Webarchive|url=https://web.archive.org/web/20150713191835/http://gallica.bnf.fr/ark:/12148/bpt6k3007r/f817.image |date=13 July 2015 }} (Note on a new series of organic compounds, tetra-carbon hydride and its derivatives), Comptes rendus, series 3, 50: 805–808. Berthelot's empirical formula for acetylene (C₄H₂), as well as the alternative name "quadricarbure d'hydrogène" (hydrogen quadricarbide), were incorrect because many chemists at that time used the wrong atomic mass for carbon (6 instead of 12).{{cite journal |last1=Ihde |first1=Aaron J. |title=The Karlsruhe Congress: A centennial retrospective |journal=Journal of Chemical Education |date=1961 |volume=38 |issue=2 |page=83 |doi=10.1021/ed038p83 |bibcode=1961JChEd..38...83I |url=https://pubs.acs.org/doi/abs/10.1021/ed038p83 |access-date=29 December 2021 |quote=Atomic weights of 6 and 12 were both in use for carbon. |archive-date=30 December 2021 |archive-url=https://web.archive.org/web/20211230033049/https://pubs.acs.org/doi/abs/10.1021/ed038p83 |url-status=live |url-access=subscription }} Berthelot was able to prepare this gas by passing vapours of organic compounds (methanol, ethanol, etc.) through a red hot tube and collecting the effluent. He also found that acetylene was formed by sparking electricity through mixed cyanogen and hydrogen gases. Berthelot later obtained acetylene directly by passing hydrogen between the poles of a carbon arc.Berthelot (1862) [http://gallica.bnf.fr/ark:/12148/bpt6k30115/f640.image.langEN "Synthèse de l'acétylène par la combinaison directe du carbone avec l'hydrogène"] {{Webarchive|url=https://web.archive.org/web/20200814023647/https://gallica.bnf.fr/ark:/12148/bpt6k30115/f640.image.langEN |date=14 August 2020 }} (Synthesis of acetylene by the direct combination of carbon with hydrogen), Comptes rendus, series 3, 54: 640–644.[http://chestofbooks.com/crafts/metal/Welding-Cutting/Acetylene.html Acetylene] {{Webarchive|url=https://web.archive.org/web/20120128110843/http://chestofbooks.com/crafts/metal/Welding-Cutting/Acetylene.html |date=28 January 2012}}.

Since the 1950s, acetylene has mainly been manufactured by the partial combustion of methane in the US, much of the EU, and many other countries:{{cite journal |last1=Habil |first1=Phil |last2=Sachsse |first2=Hans |date=1954 |title=Herstellung von Acetylen durch unvollständige Verbrennung von Kohlenwasserstoffen mit Sauerstoff (Production of acetylene by incomplete combustion of hydrocarbons with oxygen) |journal=Chemie Ingenieur Technik |volume=26 |issue=5 |pages=245–253 |doi=10.1002/cite.330260502}}{{cite journal |last1=Habil |first1=Phil |last2=Bartholoméa |first2=E. |date=1954 |title=Probleme großtechnischer Anlagen zur Erzeugung von Acetylen nach dem Sauerstoff-Verfahren (Problems of large-scale plants for the production of acetylene by the oxygen method) |journal=Chemie Ingenieur Technik |volume=26 |issue=5 |pages=253–258 |doi=10.1002/cite.330260503}}

: {{chem2|3 CH4 + 3 O2 -> C2H2 + CO + 5 H2O}}

It is a recovered side product in production of ethylene by cracking of hydrocarbons. Approximately 400,000 tonnes were produced by this method in 1983. Its presence in ethylene is usually undesirable because of its explosive character and its ability to poison Ziegler–Natta catalysts. It is selectively hydrogenated into ethylene, usually using Pd–Ag catalysts.[http://science.enotes.com/how-products-encyclopedia/acetylene Acetylene: How Products are Made] {{webarchive|url=https://web.archive.org/web/20070120055804/http://science.enotes.com/how-products-encyclopedia/acetylene|date=20 January 2007}}

The heaviest alkanes in petroleum and natural gas are cracked into lighter molecules which are dehydrogenated at high temperature:

: {{chem2|C2H6 -> C2H2 + 2 H2}}

: {{chem2|2 CH4 -> C2H2 + 3 H2}}

This last reaction is implemented in the process of anaerobic decomposition of methane by microwave plasma.{{Cite web |title=How it Works |url=https://www.transformmaterials.com/howitworks/ |access-date=2023-07-21 |website=Transform Materials |language=en-US}}

The first acetylene produced was by Edmund Davy in 1836, via potassium carbide.{{cite web |last1=Institution |first1=Smithsonian |title=Carbide Lamps |url=https://www.si.edu/spotlight/mining-lights-and-hats/carbide-lamps |website=Smithsonian Institution |language=en}}

Acetylene was historically produced by hydrolysis (reaction with water) of calcium carbide:

:{{chem2|CaC2 + 2 H2O -> Ca(OH)2 + C2H2}}

This reaction was discovered by Friedrich Wöhler in 1862,Wohler (1862) [https://books.google.com/books?id=6zIzAAAAYAAJ&pg=RA1-PA220 "Bildung des Acetylens durch Kohlenstoffcalcium"] {{Webarchive|url=https://web.archive.org/web/20160512225014/https://books.google.com/books?id=6zIzAAAAYAAJ&pg=RA1-PA220|date=12 May 2016}} (Formation of actylene by calcium carbide), Annalen der Chemie und Pharmacie, 124: 220. but a suitable commercial scale production method which allowed acetylene to be put into wider scale use was not found until 1892 by the Canadian inventor Thomas Willson while searching for a viable commercial production method for aluminum.{{cite web |title=A National Historic Chemical Landmark - Discovery of the Commercial Processes For Making Calcium Carbide and Acetylene - Commemorative Booklet |url=https://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/calciumcarbideacetylene/commericialization-of-calcium-carbide-and-acetylene-commemorative-booklet.pdf |website=American Chemical Society |publisher=ACS Office of Communications |access-date=10 October 2024 |date=1998}}

As late as the early 21st century, China, Japan, and Eastern Europe produced acetylene primarily by this method.{{cite book |doi=10.1002/0471238961.0103052007011414.a01 |chapter=Acetylene from Hydrocarbons |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2000 |last1=Gannon |first1=Richard E. |isbn=9780471484943 }}{{quotation needed|date=October 2024}}

The use of this technology has since declined worldwide with the notable exception of China, with its emphasis on coal-based chemical industry, as of 2013. Otherwise oil has increasingly supplanted coal as the chief source of reduced carbon.{{cite book |doi=10.1002/14356007.a04_533.pub2 |chapter=Calcium Carbide |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2013 |last1=Holzrichter |first1=Klaus |last2=Knott |first2=Alfons |last3=Mertschenk |first3=Bernd |last4=Salzinger |first4=Josef |pages=1–14 |isbn=978-3-527-30673-2 }}

Calcium carbide production requires high temperatures, ~2000 °C, necessitating the use of an electric arc furnace. In the US, this process was an important part of the late-19th century revolution in chemistry enabled by the massive hydroelectric power project at Niagara Falls.{{cite journal |last=Freeman |first=Horace |year=1919 |title=Manufacture of Cyanamide |url=https://books.google.com/books?id=5SAzAQAAMAAJ&q=calcium+carbide&pg=PA232 |url-status=live |journal=The Chemical News and the Journal of Physical Science |volume=117 |page=232 |archive-url=https://web.archive.org/web/20210415083126/https://books.google.com/books?id=5SAzAQAAMAAJ&q=calcium+carbide&pg=PA232 |archive-date=15 April 2021 |access-date=2013-12-23}}

File:Structure of acetylene with bond lengths and angles labeled.svg

In terms of valence bond theory, in each carbon atom the 2s orbital hybridizes with one 2p orbital thus forming an sp hybrid. The other two 2p orbitals remain unhybridized. The two ends of the two sp hybrid orbital overlap to form a strong σ valence bond between the carbons, while on each of the other two ends hydrogen atoms attach also by σ bonds. The two unchanged 2p orbitals form a pair of weaker π bonds.Organic Chemistry 7th ed. by J. McMurry, Thomson 2008

Since acetylene is a linear symmetrical molecule, it possesses the D_∞h point group.{{Housecroft3rd|pages=94–95}}

At atmospheric pressure, acetylene cannot exist as a liquid and does not have a melting point. The triple point on the phase diagram corresponds to the melting point (−80.8 °C) at the minimal pressure at which liquid acetylene can exist (1.27 atm). At temperatures below the triple point, solid acetylene can change directly to the vapour (gas) by sublimation. The sublimation point at atmospheric pressure is −84.0 °C.Handbook of Chemistry and Physics (60th ed., CRC Press 1979–80), p. C-303 in Table Physical Constants of Organic Compounds (listed as ethyne).

At room temperature, the solubility of acetylene in acetone is 27.9 g per kg. For the same amount of dimethylformamide (DMF), the solubility is 51 g. At

20.26 bar, the solubility increases to 689.0 and 628.0 g for acetone and DMF, respectively. These solvents are used in pressurized gas cylinders.

Approximately 20% of acetylene is supplied by the industrial gases industry for oxyacetylene gas welding and cutting due to the high temperature of the flame. Combustion of acetylene with oxygen produces a flame of over {{convert|3600|K|C F}}, releasing 11.8 kJ/g. Oxygen with acetylene is the hottest burning common gas mixture.{{cite web |url=http://www.linde-gas.com/en/products_and_supply/gases_fuel/acetylene.html |title=Acetylene |access-date=2013-11-30 |publisher=Linde |website=Products and Supply > Fuel Gases |archive-date=12 January 2018 |archive-url=https://web.archive.org/web/20180112184128/http://www.linde-gas.com/en/products_and_supply/gases_fuel/acetylene.html |url-status=live }} Acetylene is the third-hottest natural chemical flame after dicyanoacetylene's {{convert|5260|K|C F}} and cyanogen at {{convert|4798|K|C F}}. Oxy-acetylene welding was a popular welding process in previous decades. The development and advantages of arc-based welding processes have made oxy-fuel welding nearly extinct for many applications. Acetylene usage for welding has dropped significantly. On the other hand, oxy-acetylene welding equipment is quite versatile – not only because the torch is preferred for some sorts of iron or steel welding (as in certain artistic applications), but also because it lends itself easily to brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), the loosening of corroded nuts and bolts, and other applications. Bell Canada cable-repair technicians still use portable acetylene-fuelled torch kits as a soldering tool for sealing lead sleeve splices in manholes and in some aerial locations. Oxyacetylene welding may also be used in areas where electricity is not readily accessible. Oxyacetylene cutting is used in many metal fabrication shops. For use in welding and cutting, the working pressures must be controlled by a regulator, since above {{convert|15|psi|abbr=on}}, if subjected to a shockwave (caused, for example, by a flashback), acetylene decomposes explosively into hydrogen and carbon.[http://www.esabna.com/euweb/oxy_handbook/589oxy3_3.htm ESAB Oxy-acetylene welding handbook – Acetylene properties] {{Webarchive|url=https://web.archive.org/web/20200510192947/https://www.esabna.com/euweb/oxy_handbook/589oxy3_3.htm |date=10 May 2020 }}.

File:Laskarbit.jpg]]

Acetylene is useful for many processes, but few are conducted on a commercial scale.{{cite journal |doi=10.1021/cr400357r |title=Catalytic Reactions of Acetylene: A Feedstock for the Chemical Industry Revisited |date=2014 |last1=Trotuş |first1=Ioan-Teodor |last2=Zimmermann |first2=Tobias |last3=Schüth |first3=Ferdi |journal=Chemical Reviews |volume=114 |issue=3 |pages=1761–1782 |pmid=24228942 |doi-access=free }}

One of the major chemical applications is ethynylation of formaldehyde.

Acetylene adds to aldehydes and ketones to form α-ethynyl alcohols:

:300px

The reaction gives butynediol, with propargyl alcohol as the by-product. Copper acetylide is used as the catalyst.{{Citation |last1=Gräfje |first1=Heinz |title=Butanediols, Butenediol, and Butynediol |date=2000-06-15 |url=https://onlinelibrary.wiley.com/doi/10.1002/14356007.a04_455 |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |pages=a04_455 |editor-last=Wiley-VCH Verlag GmbH & Co. KGaA |place=Weinheim, Germany |publisher=Wiley-VCH Verlag GmbH & Co. KGaA |language=en |doi=10.1002/14356007.a04_455 |isbn=978-3-527-30673-2 |access-date=2022-03-03 |last2=Körnig |first2=Wolfgang |last3=Weitz |first3=Hans-Martin |last4=Reiß |first4=Wolfgang |last5=Steffan |first5=Guido |last6=Diehl |first6=Herbert |last7=Bosche |first7=Horst |last8=Schneider |first8=Kurt |last9=Kieczka |first9=Heinz |s2cid=178601434 |archive-date=19 March 2022 |archive-url=https://web.archive.org/web/20220319160632/https://onlinelibrary.wiley.com/doi/10.1002/14356007.a04_455 |url-status=live |url-access=subscription }}{{Citation |last1=Falbe |first1=Jürgen |title=Alcohols, Aliphatic |date=2000-06-15 |url=https://onlinelibrary.wiley.com/doi/10.1002/14356007.a01_279 |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |pages=a01_279 |editor-last=Wiley-VCH Verlag GmbH & Co. KGaA |place=Weinheim, Germany |publisher=Wiley-VCH Verlag GmbH & Co. KGaA |language=en |doi=10.1002/14356007.a01_279 |isbn=978-3-527-30673-2 |access-date=2022-03-03 |last2=Bahrmann |first2=Helmut |last3=Lipps |first3=Wolfgang |last4=Mayer |first4=Dieter |archive-date=9 March 2022 |archive-url=https://web.archive.org/web/20220309153410/https://onlinelibrary.wiley.com/doi/10.1002/14356007.a01_279 |url-status=live|url-access=subscription }}

In addition to ethynylation, acetylene reacts with carbon monoxide to give acrylic acid, or acrylic esters. Metal catalysts are required. These derivatives form products such as acrylic fibers, glasses, paints, resins, and polymers. Except in China, use of acetylene as a chemical feedstock has declined by 70% from 1965 to 2007 owing to cost and environmental considerations.{{cite journal|author1=Takashi Ohara|author2=Takahisa Sato|author3=Noboru Shimizu|author4=Günter Prescher|author5=Helmut Schwind|author6=Otto Weiberg|author7=Klaus Marten|author8=Helmut Greim|title=Acrylic Acid and Derivatives|journal=Ullmann's Encyclopedia of Industrial Chemistry|year=2003|page=7|doi=10.1002/14356007.a01_161.pub2|isbn=3527306730 }} In China, acetylene is a major precursor to vinyl chloride.

Prior to the widespread use of petrochemicals, coal-derived acetylene was a building block for several industrial chemicals. Thus acetylene can be hydrated to give acetaldehyde, which in turn can be oxidized to acetic acid. Processes leading to acrylates were also commercialized. Almost all of these processes became obsolete with the availability of petroleum-derived ethylene and propylene.{{cite journal |doi=10.1021/cr400276u |title=Production of Acetylene and Acetylene-based Chemicals from Coal |date=2014 |last1=Schobert |first1=Harold |journal=Chemical Reviews |volume=114 |issue=3 |pages=1743–1760 |pmid=24256089 }}

In 1881, the Russian chemist Mikhail Kucherov{{Cite journal|doi=10.1002/cber.188101401320|title=Ueber eine neue Methode direkter Addition von Wasser (Hydratation) an die Kohlenwasserstoffe der Acetylenreihe|year=1881|last1=Kutscheroff|first1=M.|journal=Berichte der Deutschen Chemischen Gesellschaft|volume=14|pages=1540–1542|url=https://zenodo.org/record/1425226|access-date=9 September 2019|archive-date=2 December 2020|archive-url=https://web.archive.org/web/20201202225306/https://zenodo.org/record/1425226|url-status=live}} described the hydration of acetylene to acetaldehyde using catalysts such as mercury(II) bromide. Before the advent of the Wacker process, this reaction was conducted on an industrial scale.{{cite journal | title = Hydration of Acetylene: A 125th Anniversary | author1 = Dmitry A. Ponomarev | author2 = Sergey M. Shevchenko | journal = J. Chem. Educ. | volume = 84 | issue = 10 | year = 2007 | page = 1725 | url = http://jchemed.chem.wisc.edu/HS/Journal/Issues/2007/OctACS/ACSSub/p1725.pdf | doi = 10.1021/ed084p1725 | bibcode = 2007JChEd..84.1725P | access-date = 18 February 2009 | archive-date = 11 June 2011 | archive-url = https://web.archive.org/web/20110611190527/http://jchemed.chem.wisc.edu/HS/Journal/Issues/2007/OctACS/ACSSub/p1725.pdf | url-status = live }}

The polymerization of acetylene with Ziegler–Natta catalysts produces polyacetylene films. Polyacetylene, a chain of CH centres with alternating single and double bonds, was one of the first discovered organic semiconductors. Its reaction with iodine produces a highly electrically conducting material. Although such materials are not useful, these discoveries led to the developments of organic semiconductors, as recognized by the Nobel Prize in Chemistry in 2000 to Alan J. Heeger, Alan G MacDiarmid, and Hideki Shirakawa.

In the 1920s, pure acetylene was experimentally used as an inhalation anesthetic.{{cite encyclopedia |year=1930 |title=Acetylene in medicine|encyclopedia=Encyclopaedia Britannica |edition=14|volume=1|page=119 |author=William Stanley Sykes |author-link=William Stanley Sykes |language=en}}

Acetylene is sometimes used for carburization (that is, hardening) of steel when the object is too large to fit into a furnace.{{cite web |url=http://boc.com/products_and_services/by_product/acetylene/index.asp |title=Acetylene |publisher=BOC |website=Products and Services |archive-url=https://web.archive.org/web/20060517074022/http://boc.com/products_and_services/by_product/acetylene/index.asp |archive-date=2006-05-17 }}

Acetylene is used to volatilize carbon in radiocarbon dating. The carbonaceous material in an archeological sample is treated with lithium metal in a small specialized research furnace to form lithium carbide (also known as lithium acetylide). The carbide can then be reacted with water, as usual, to form acetylene gas to feed into a mass spectrometer to measure the isotopic ratio of carbon-14 to carbon-12.{{cite journal|last=Geyh, Mebus|title=Radiocarbon dating problems using acetylene as counting gas|journal=Radiocarbon|year=1990|volume=32|issue=3|pages=321–324|doi=10.2458/azu_js_rc.32.1278|url=https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1278/1283|access-date=2013-12-26|archive-date=26 December 2013|archive-url=https://web.archive.org/web/20131226194553/https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1278/1283|url-status=live|doi-access=free}}

Acetylene combustion produces a strong, bright light and the ubiquity of carbide lamps drove much acetylene commercialization in the early 20th century. Common applications included coastal lighthouses,{{Cite web|title=Lighthouse Lamps Through Time by Thomas Tag {{!}} US Lighthouse Society|url=http://uslhs.org/lighthouse-lamps-through-time|access-date=2017-02-24|website=uslhs.org|language=en|archive-date=25 February 2017|archive-url=https://web.archive.org/web/20170225130406/http://uslhs.org/lighthouse-lamps-through-time|url-status=live}} street lights,

{{Cite book|last=Myers|first=Richard L.|url=https://books.google.com/books?id=0AnJU-hralEC|title=The 100 Most Important Chemical Compounds: A Reference Guide|date=2007|publisher=ABC-CLIO|isbn=978-0-313-33758-1|language=en|pages=7-9|access-date=21 November 2015|archive-date=17 June 2016|archive-url=https://web.archive.org/web/20160617093705/https://books.google.com/books?id=0AnJU-hralEC|url-status=live}} and automobileGrainger, D., (2001). By cars' early light: A short history of the headlamp: 1900s lights bore port and starboard red and green lenses. National Post. [Toronto Edition] DT7. and mining headlamps.{{cite book|last=Thorpe|first=Dave|title=Carbide Light: The Last Flame in American Mines|publisher=Bergamot Publishing|year=2005|isbn=978-0976090526}} In most of these applications, direct combustion is a fire hazard, and so acetylene has been replaced, first by incandescent lighting and many years later by low-power/high-lumen LEDs. Nevertheless, acetylene lamps remain in limited use in remote or otherwise inaccessible areas and in countries with a weak or unreliable central electric grid.

The energy richness of the C≡C triple bond and the rather high solubility of acetylene in water make it a suitable substrate for bacteria, provided an adequate source is available.{{Cite journal |last=Akob |first=Denise |date=August 2018 |title=Acetylenotrophy: a hidden but ubiquitous microbial metabolism? |url=https://academic.oup.com/femsec/article/94/8/fiy103/5026170 |access-date=2022-07-28 |journal=FEMS Microbiology Ecology|volume=94 |issue=8 |doi=10.1093/femsec/fiy103 |pmid=29933435 |pmc=7190893 }} A number of bacteria living on acetylene have been identified. The enzyme acetylene hydratase catalyzes the hydration of acetylene to give acetaldehyde:{{cite book|first1=Felix|last1=ten Brink|editor=Peter M. H. Kroneck and Martha E. Sosa Torres|title=The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment|series=Metal Ions in Life Sciences|volume=14|year=2014|publisher=Springer|chapter=Chapter 2. Living on acetylene. A Primordial Energy Source|pages=15–35|doi=10.1007/978-94-017-9269-1_2|pmid=25416389|isbn=978-94-017-9268-4 }}

:{{chem2|C2H2 + H2O -> CH3CHO}}

Acetylene is a moderately common chemical in the universe, often associated with the atmospheres of gas giants.{{cite press release|publisher=W. M. Keck Observatory |title=Precursor to Proteins and DNA found in Stellar Disk |date=20 December 2005 |url=http://www.keckobservatory.org/article.php?id=39 |url-status=dead |archive-url=https://web.archive.org/web/20070223211405/http://www.keckobservatory.org/article.php?id=39 |archive-date=2007-02-23 }} One curious discovery of acetylene is on Enceladus, a moon of Saturn. Natural acetylene is believed to form from catalytic decomposition of long-chain hydrocarbons at temperatures of {{convert|1700|K|C F}} and above. Since such temperatures are highly unlikely on such a small distant body, this discovery is potentially suggestive of catalytic reactions within that moon, making it a promising site to search for prebiotic chemistry.{{cite web|publisher=The Planetary Society |author =Emily Lakdawalla |title=LPSC: Wednesday afternoon: Cassini at Enceladus |date=17 March 2006 |url=http://www.planetary.org/blog/article/00000498/ |url-status=dead |archive-url=https://web.archive.org/web/20120220053655/http://www.planetary.org/blog/article/00000498/ |archive-date=2012-02-20 }}{{cite journal|journal=Nature | volume=445 | pages=376–377| date= 25 January 2007| doi = 10.1038/445376b| title= Planetary science: Inside Enceladus|author1=John Spencer |author2=David Grinspoon |pmid=17251967|issue=7126| bibcode=2007Natur.445..376S | s2cid=4427890 | doi-access=free}}

In vinylation reactions, H−X compounds add across the triple bond. Alcohols and phenols add to acetylene to give vinyl ethers. Thiols give vinyl thioethers. Similarly, vinylpyrrolidone and vinylcarbazole are produced industrially by vinylation of 2-pyrrolidone and carbazole.{{Ullmann|first1=Albrecht Ludwig|last1=Harreus|first2=R.|last2=Backes|first3=J.-O.|last3=Eichler|first4=R.|last4=Feuerhake|first5=C. |last5=Jäkel|first6=U.|last6=Mahn|first7=R.|last7=Pinkos|first8=R.|last8=Vogelsang|title=2-Pyrrolidone|year=2011|doi=10.1002/14356007.a22_457.pub2}}

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The hydration of acetylene is a vinylation reaction, but the resulting vinyl alcohol isomerizes to acetaldehyde. The reaction is catalyzed by mercury salts. This reaction once was the dominant technology for acetaldehyde production, but it has been displaced by the Wacker process, which affords acetaldehyde by oxidation of ethylene, a cheaper feedstock. A similar situation applies to the conversion of acetylene to the valuable vinyl chloride by hydrochlorination versus the oxychlorination of ethylene.

Vinyl acetate is used instead of acetylene for some vinylations, which are more accurately described as transvinylations.{{cite book |doi=10.1002/047084289X.rv008|chapter=Vinyl Acetate |title=Encyclopedia of Reagents for Organic Synthesis |year=2001 |last1=Manchand |first1=Percy S. |isbn=0471936235 }} Higher esters of vinyl acetate have been used in the synthesis of vinyl formate.

Acetylene and its derivatives (2-butyne, diphenylacetylene, etc.) form complexes with transition metals. Its bonding to the metal is somewhat similar to that of ethylene complexes. These complexes are intermediates in many catalytic reactions such as alkyne trimerisation to benzene, tetramerization to cyclooctatetraene, and carbonylation to hydroquinone:{{cite journal|author1=Reppe, Walter |author2=Kutepow, N |author3=Magin, A |title=Cyclization of Acetylenic Compounds|journal=Angewandte Chemie International Edition in English|year=1969|volume=8|issue=10|pages=727–733 |doi=10.1002/anie.196907271 }}

:240px

:240px

:{{chem2|Fe(CO)5 + 4 C2H2 + 2 H2O -> 2 C6H4(OH)2 + FeCO3}} at basic conditions (50–{{val|80|u=degC}}, 20–{{val|25|u=atm}}).

Metal acetylides, species of the formula {{chem2|L_{n}M\sC2R}}, are also common. Copper(I) acetylide and silver acetylide can be formed in aqueous solutions with ease due to a favorable solubility equilibrium.

{{Main|Acetylide#Preparation}}

Acetylene has a pK_a of 25. Acetylene can be deprotonated by a superbase to form an acetylide:{{cite book|last1=Viehe|first1=Heinz Günter|title=Chemistry of Acetylenes|url=https://archive.org/details/chemistryofacety0000vieh|url-access=registration|date=1969|publisher=Marcel Dekker, inc.|location=New York|pages=170–179 & 225–241|edition=1st|isbn=978-0824716752}}

:{{chem2 | HC\tCH + RM -> RH + HC\tCM }}

Various organometallic{{Cite journal|last1=Midland|first1=M. M.|last2=McLoughlin|first2=J. I.|last3=Werley|first3=Ralph T. (Jr.)|date=1990|title=Preparation and Use of Lithium Acetylide: 1-Methyl-2-ethynyl-endo-3,3-dimethyl-2-norbornanol|journal=Organic Syntheses|volume=68|page=14|doi=10.15227/orgsyn.068.0014}} and inorganic{{cite journal|last1=Coffman|first1=Donald D.|title=Dimethylethhynylcarbinol|journal=Organic Syntheses|date=1940|volume=40|page=20|doi=10.15227/orgsyn.020.0040}} reagents are effective.

Image:BASF_Nsw.jpg, commissioned in 2020]]

Acetylene can be semihydrogenated to ethylene, providing a feedstock for a variety of polyethylene plastics. Halogens add to the triple bond.

Acetylene is not especially toxic, but when generated from calcium carbide, or CaC₂, it can contain toxic impurities such as traces of phosphine and arsine, which gives it a distinct garlic-like smell. It is also highly flammable, as are most light hydrocarbons, hence its use in welding. Its most singular hazard is associated with its intrinsic instability, especially when it is pressurized: under certain conditions acetylene can react in an exothermic addition-type reaction to form a number of products, typically benzene and/or vinylacetylene, possibly in addition to carbon and hydrogen.{{Citation needed|date=December 2016}} Although it is stable at normal pressures and temperatures, if it is subjected to pressures as low as 15 psig it can explode. The safe limit for acetylene therefore is 101 kPa_gage, or 15 psig.{{cite web | url = http://www.c-f-c.com/specgas_products/acetylene.htm | title = Acetylene Specification | access-date = 2012-05-02 | publisher = CFC StarTec LLC | archive-date = 11 March 2014 | archive-url = https://web.archive.org/web/20140311222208/http://www.c-f-c.com/specgas_products/acetylene.htm | url-status = live }}{{Cite web|url=https://law.resource.org/pub/us/cfr/ibr/003/cga.g-1.2009.pdf|title=law.resource.org CGA g-1 2009 (incorporated by reference)|access-date=2016-11-30|archive-date=10 October 2016|archive-url=https://web.archive.org/web/20161010200240/https://law.resource.org/pub/us/cfr/ibr/003/cga.g-1.2009.pdf|url-status=live}} Additionally, if acetylene is initiated by intense heat or a shockwave, it can decompose explosively if the absolute pressure of the gas exceeds about {{convert|200|kPa|psi}}. It is therefore supplied and stored dissolved in acetone or dimethylformamide (DMF),{{cite book | last1 = Downie | first1 = N. A. | title = Industrial Gases | publisher = Blackie Academic & Professional | year = 1997 | location = London; New York | isbn = 978-0-7514-0352-7}}{{cite book|first=Mikołaj|last=Korzun|title=1000 słów o materiałach wybuchowych i wybuchu|isbn=83-11-07044-X|year=1986|location=Warszawa|publisher=Wydawnictwo Ministerstwa Obrony Narodowej|oclc=69535236}} contained in a gas cylinder with a porous filling, which renders it safe to transport and use, given proper handling. Acetylene cylinders should be used in the upright position to avoid withdrawing acetone during use.{{Cite web|url=http://eiga.web1.apollo-com.be/fileadmin/docs_pubs/Doc_123_13_Code_of_Practice_Acetylene.pdf|title=EIGA Code of Practice: Acetylene|access-date=2016-11-30|archive-url=https://web.archive.org/web/20161201014426/http://eiga.web1.apollo-com.be/fileadmin/docs_pubs/Doc_123_13_Code_of_Practice_Acetylene.pdf|archive-date=1 December 2016|url-status=dead}}

Information on safe storage of acetylene in upright cylinders is provided by the OSHA,{{Cite web|url=https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9748|title=OSHA 29 CFR 1910.102 Acetylene|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201080130/https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9748|url-status=live}}{{Cite web|url=https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10696|title=OSHA 29 CFR 1926.350 Gas Welding and cutting.|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201012751/https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10696|url-status=live}} Compressed Gas Association, United States Mine Safety and Health Administration (MSHA),[http://arlweb.msha.gov/alerts/hazardsofacetylene.htm Special Hazards of Acetylene] {{Webarchive|url=https://web.archive.org/web/20160324115350/http://arlweb.msha.gov/alerts/hazardsofacetylene.htm |date=24 March 2016 }} UNITED STATES DEPARTMENT OF LABOR Mine Safety and Health Administration – MSHA. EIGA, and other agencies.

Copper catalyses the decomposition of acetylene, and as a result acetylene should not be transported in copper pipes.{{cite web|url=http://www.brown.edu/Administration/EHS/lab/assets/SA-2.2003.pdf|date=2003-10-16|author=Daniel_Sarachick|title=ACETYLENE SAFETY ALERT|publisher=Office of Environmental Health & Safety (EHS)|access-date=2018-09-27|archive-date=13 July 2018|archive-url=https://web.archive.org/web/20180713033908/http://www.brown.edu/Administration/EHS/lab/assets/SA-2.2003.pdf|url-status=live}}

Cylinders should be stored in an area segregated from oxidizers to avoid exacerbated reaction in case of fire/leakage. Acetylene cylinders should not be stored in confined spaces, enclosed vehicles, garages, and buildings, to avoid unintended leakage leading to explosive atmosphere. In the US, National Electric Code (NEC) requires consideration for hazardous areas including those where acetylene may be released during accidents or leaks.{{Cite web|url=http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=70&tab=editions|title=NFPA free access to 2017 edition of NFPA 70 (NEC)|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201075712/http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=70&tab=editions|url-status=live}} Consideration may include electrical classification and use of listed Group A electrical components in US. Further information on determining the areas requiring special consideration is in NFPA 497.{{Cite web|url=http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=497&tab=editions|title=NFPA Free Access to NFPA 497 – Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201015905/http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=497&tab=editions|url-status=live}} In Europe, ATEX also requires consideration for hazardous areas where flammable gases may be released during accidents or leaks.

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• [http://pureacetylenegenerator.com Acetylene Production Plant and Detailed Process] {{Webarchive|url=https://web.archive.org/web/20150411085620/http://www.pureacetylenegenerator.com/ |date=11 April 2015 }}
• [http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG07/MENU.HTM Acetylene at Chemistry Comes Alive!]
• {{Gutenberg|name=Acetylene, the Principles of Its Generation and Use|no=8144}}
• [https://www.youtube.com/watch?v=KXh7__ri1VQ Movie explaining acetylene formation from calcium carbide and the explosive limits forming fire hazards]
• [http://www.periodicvideos.com/videos/mv_calcium_carbide.htm Calcium Carbide & Acetylene] at The Periodic Table of Videos (University of Nottingham)
• [https://www.cdc.gov/niosh/npg/npgd0008.html CDC – NIOSH Pocket Guide to Chemical Hazards – Acetylene]

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