Oxalyl chloride

Oxalyl chloride was first prepared in 1892 by the French chemist Adrien Fauconnier, who treated diethyl oxalate with phosphorus pentachloride.{{cite journal|last1=Fauconnier|first1=Adrien|title=Action du perchlorure de phosphore sur l'oxalate d'éthyle|journal=Comptes rendus hebdomadaires des séances de l'Académie des Sciences|date=1892|volume=114|pages=122–123|url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d00008437c;view=1up;seq=132|trans-title=The action of phosphorus pentachloride on diethyl oxalate|language=fr}} It can also be prepared by treating oxalic acid with phosphorus pentachloride.{{cite patent |inventor= Vogel, A.; Steffan, G.; Mannes, K.; Trescher, V. |title= Process for the preparation of oxalyl chloride |country= DE |number= 2840435 |status= patent |gdate= 1980-03-27 |assign1= Bayer}}{{cite journal |doi=10.1002/cber.19080410335 |title=Oxalylchlorid |date=1908 |last1=Staudinger |first1=H. |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=41 |issue=3 |pages=3558–3566 }}

Oxalyl chloride is produced commercially from ethylene carbonate. Photochlorination gives the perchloroethylene carbonate {{chem2|C2Cl4O2CO}} and hydrogen chloride HCl, which is subsequently degraded to oxalyl chloride and phosgene {{chem2|COCl2}}:{{Ullmann |doi=10.1002/14356007.a19_573|title=Photochemistry|year=2000|last1=Pfoertner|first1=Karl-Heinz|isbn=3527306730}}

:{{chem2|C2H4O2CO + 4 Cl2 → C2Cl4O2CO + 4 HCl}}

:{{chem2|C2Cl4O2CO → C2O2Cl2 + COCl2}}

As originally determined by Staudinger, oxalyl chloride reacts with water giving off gaseous products only: hydrogen chloride (HCl), carbon dioxide ({{chem2|CO2}}), and carbon monoxide (CO).{{cite journal |doi=10.1021/acs.orglett.5b01252 |title=Oxalyl Chloride as a Practical Carbon Monoxide Source for Carbonylation Reactions |date=2015 |last1=Hansen |first1=Steffen V. F. |last2=Ulven |first2=Trond |journal=Organic Letters |volume=17 |issue=11 |pages=2832–2835 |pmid=26000869 }}

:{{chem2|(COCl)2 + H2O → 2 HCl + CO2 + CO}}

Other acyl chlorides hydrolyze with formation of hydrogen chloride and the original carboxylic acid.

Addition of a primary or secondary alcohol to a solution of oxalyl chloride in DMSO, followed by quenching with an organic base such as triethylamine converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.{{OrgSynth|author= Dondoni, A.|author2= Perrone, D.|title= Synthesis of 1,1-Dimethyl Ethyl-(S)-4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate by Oxidation of the Alcohol|collvol= 10|collvolpages= 320|year= 2004|prep= v77p0064}}{{OrgSynth|author= Bishop, R.|title= 9-Thiabicyclo[3.3.1]nonane-2,6-dione|collvol= 9|collvolpages= 692|year= 1998|prep= cv9p0692}}{{OrgSynth|author= Leopold, E. J.|title= Selective hydroboration of a 1,3,7-triene: Homogeraniol|collvol= 7|collvolpages= 258|year= 1990|prep= cv7p0258}}

Oxalyl chloride is mainly used together with a N,N-dimethylformamide catalyst in organic synthesis for the preparation of acyl chlorides from the corresponding carboxylic acids.{{cn|date=January 2025}} Like thionyl chloride, the reagent degrades into volatile side products in this application, which simplifies workup. One of the minor byproducts from the N,N-dimethylformamide catalyzed reaction, dimethylcarbamoyl chloride, is a potent carcinogen, stemming from the N,N-dimethylformamide decomposition.{{cite book|last=Clayden|first=Jonathan|title=Organic chemistry|year=2005|publisher=Oxford Univ. Press|location=Oxford [u.a.]|isbn=978-0-19-850346-0|pages=[https://archive.org/details/organicchemistry00clay_0/page/296 296]|edition=Reprinted(with corrections)|url-access=registration|url=https://archive.org/details/organicchemistry00clay_0/page/296}}{{cite journal |last=Levin |first=D. |title=Potential Toxicological Concerns Associated with Carboxylic Acid Chlorination and Other Reactions |journal=Organic Process Research & Development |publisher=American Chemical Society |year=1997 |volume=1 |issue=2 |page=182 |doi=10.1021/op970206t}} Relative to thionyl chloride, oxalyl chloride tends to be a milder, more selective reagent. It is also more expensive than thionyl chloride so it tends to be used on a smaller scale.

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This reaction involves conversion of N,N-dimethylformamide to the imidoyl chloride derivative (chloromethylene(dimethyl)ammonium ion {{chem2|(CH3)2N+\dCHCl}}), akin to the first stage in the Vilsmeier–Haack reaction. The imidoyl chloride is the active chlorinating agent.

Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chloride to give the corresponding acyl chloride in a process known as a Friedel-Crafts acylation.{{OrgSynth|author= Neubert, M. E.|author2= Fishel, D. L.|title= Preparation of 4-Alkyl- and 4-Halobenzoyl Chlorides: 4-Pentylbenzoyl Chloride|year= 1983|volume= 61|pages= 8|collvol= 7|collvolpages= 420|prep= cv7p0420}}{{OrgSynth|author= Sokol, P. E.|title= Mesitoic Acid|year= 1964|volume= 44|pages= 69|collvol= 5|collvolpages= 706|prep= CV5P0706}} The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.

Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:

:{{chem2|2 R\sCH2\sOH + Cl\sC(\dO)\sC(\dO)Cl → R\sCH2\sO\sC(\dO)\sC(\dO)\sO\sCH2\sR + 2 HCl}}

Typically, such reactions are conducted in the presence of a base such as pyridine. The diester derived from phenol, phenyl oxalate ester, is Cyalume, the active ingredient in glow sticks.{{citation needed|date=September 2024}}

A similar reaction occurs with amines to give substituted oxalamides:{{cite journal|doi=10.1039/D0SC02065F |title=Synthesis of oxalamides by acceptorless dehydrogenative coupling of ethylene glycol and amines and the reverse hydrogenation catalyzed by ruthenium |date=2020 |last1=Zou |first1=You-Quan |last2=Zhou |first2=Quan-Quan |last3=Diskin-Posner |first3=Yael |last4=Ben-David |first4=Yehoshoa |last5=Milstein |first5=David |journal=Chemical Science |volume=11 |issue=27 |pages=7188–7193 |pmid=34123004 |pmc=8159388 }}

:{{chem2|2 R\sNH2 + ClC(\dO)\sC(\dO)Cl -> R\sNH\sC(\dO)\sC(\dO)\sNH\sR + 2 HCl}}

Oxalyl chloride was reportedly used in the first synthesis of dioxane tetraketone ({{chem2|C4O6}}), an oxide of carbon.{{cite journal |title= The reaction between ethanedioyl (oxalyl) dihalides and Ag₂C₂O₄: a route to Staudinger's elusive ethanedioic (oxalic) acid anhydride |author1=Strazzolini, P. |author2=Gambi, A. |author3=Giumanini, A. G. |author4=Vancik, H. |journal= Journal of the Chemical Society, Perkin Transactions 1 |year= 1998 |volume= 1998 |issue= 16 |pages= 2553–2558 |doi= 10.1039/a803430c}}

In March 2000, a Malaysia Airlines Airbus A330-300 was damaged beyond repair after a cargo of prohibited oxalyl chloride (falsely declared as hydroxyquinoline) leaked into the cargo bay.{{cite news |title= Firm told to pay $65 mln for ruining plane |date= 2007-12-06 |url= https://www.reuters.com/article/oddlyEnoughNews/idUSN0620441720071206 |publisher= Reuters |access-date= 2007-12-06}} It is toxic by inhalation, although it is over an order of magnitude less acutely toxic than the related compound phosgene.{{cite journal|last1=Barbee|first1=S.J.|last2=Stone|first2=J.J.|last3=Hilaski|first3=R.J.|date=January 1995|title=Acute Inhalation Toxicology of Oxalyl Chloride|journal=American Industrial Hygiene Association Journal|language=en|volume=56|issue=1|pages=74–76|doi=10.1080/15428119591017358|pmid=7872205|issn=0002-8894}}

• Oxalyl
• Swern oxidation

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Category:Acyl chlorides

Category:Carbon oxohalides