Editing Acetylene (section)

==Reactions==
===Vinylation reactions===
In [[vinylation]] reactions, H−X compounds add across the triple bond. [[Alcohol (chemistry)|Alcohols]] and [[phenols]] add to acetylene to give [[enol ether|vinyl ether]]s. [[Thiol|Thiols]] give vinyl thioethers. Similarly, [[vinylpyrrolidone]] and [[vinylcarbazole]] are produced industrially by vinylation of [[2-Pyrrolidone|2-pyrrolidone]] and [[carbazole]].<ref name=Ull>{{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}}</ref><ref name=Ullmann/>
:[[File:Reppe-chemnistry-vinylization.png|300px]]

The hydration of acetylene is a vinylation reaction, but the resulting vinyl alcohol isomerizes to [[acetaldehyde]]. The reaction is catalyzed by [[Mercury (element)|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]] vs the [[oxychlorination]] of ethylene.

[[Vinyl acetate]] is used instead of acetylene for some vinylations, which are more accurately described as [[transvinylation]]s.<ref>{{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 }}</ref> Higher esters of vinyl acetate have been used in the synthesis of [[vinyl formate]].

===Organometallic chemistry===
Acetylene and its derivatives (2-butyne, diphenylacetylene, etc.) form [[Transition metal alkyne complex|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]],<ref name=Ullmann/> and carbonylation to [[hydroquinone]]:<ref name=Cyclization>{{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 }}</ref>
:[[File:Reppe-chemistry-benzene.png|240px]]
:[[File:Reppe-chemistry-cyclooctatetraene.png|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 [[acetylide]]s, 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]].<ref name=Viehe />

===Acid-base reactions===
{{Main|Acetylide#Preparation}}
Acetylene has a [[Acid dissociation constant|p''K''<sub>a</sub>]] of 25, acetylene can be [[deprotonation|deprotonated]] by a [[superbase]] to form an [[acetylide]]:<ref name=Viehe>{{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}}</ref>

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

Various [[organometallic]]<ref name=Midland1990>{{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}}</ref> and [[Inorganic compound|inorganic]]<ref name=Coffman>{{cite journal|last1=Coffman|first1=Donald D.|title=Dimethylethhynylcarbinol|journal=Organic Syntheses|date=1940|volume=40|page=20|doi=10.15227/orgsyn.020.0040}}</ref> reagents are effective.

[[Image:BASF_Nsw.jpg|thumb|The ''new acetylene plant'' of [[BASF]], commissioned in 2020]]

===Hydrogenation===
Acetylene can be [[semihydrogenation|semihydrogenated]] to [[ethylene]], providing a feedstock for a variety of [[polyethylene]] plastics.  Halogens add to the triple bond.