Diethyl oxalate
{{Chembox
| ImageFile = Ethyl oxalate.svg
| ImageSize =
| ImageAlt =
| IUPACName =
| OtherNames = ethyl oxalate
|Section1={{Chembox Identifiers
| CASNo = 95-92-1
| ChEMBL = 3183226
| ChemSpiderID = 6998
| EC_number = 202-464-1
| PubChem = 7268
| UNII = 860M3ZWF6J
| UNNumber = 2525
| StdInChI=1S/C6H10O4/c1-3-9-5(7)6(8)10-4-2/h3-4H2,1-2H3
| StdInChIKey = WYACBZDAHNBPPB-UHFFFAOYSA-N
| SMILES = CCOC(=O)C(=O)OCC
}}
|Section2={{Chembox Properties
| C=6|H=10|O=4
| MolarMass =
| RefractIndex =
| Appearance = colorless liquid
| Density = 1.0785 g/cm3
| MeltingPtC =-38.5
| MeltingPt_notes =
| BoilingPtC = 186
| BoilingPt_notes =
| Solubility = }}
|Section3={{Chembox Hazards
| GHS_ref=[https://pubchem.ncbi.nlm.nih.gov/compound/7268#section=Safety-and-Hazards]
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|319}}
| PPhrases = {{P-phrases|264|264+265|270|280|301+317|305+351+338|330|337+317|501}}
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
}}
Diethyl oxalate is an organic compound with the formula {{chem2|(CO2CH2CH3)2}}. It is the diethyl ester of oxalic acid. Diethyl oxalate is a colorless liquid. It is very similar to dimethyl oxalate but is a liquid at room temperature and has lower solubility in water. Both compounds are reagents in the synthesis of more complex compounds.{{cite book |doi=10.1002/047084289X.rd207 |chapter=Diethyl Oxalate |title=Encyclopedia of Reagents for Organic Synthesis |date=2001 |last1=Garratt |first1=Peter J. |isbn=0-471-93623-5 }}
Production
Diethyl oxalate can be obtained by esterification of oxalic acid with ethanol using sulfuric acid as a catalyst. A procedure for the closely related dimethyl oxalate is available:{{cite journal |doi=10.15227/orgsyn.010.0078|title=Methyl Oxalate|journal=Organic Syntheses|year=1930|volume=10|page=78|author=Everett Bowden}}
:{{chem2|2 CH3CH2OH + (CO2H)2 -> (CO2CH2CH3)2 + 2 H2O}}
Reactions
Diethyl oxalate participates in many condensation reactions, usually to produce esters.{{cite journal |doi=10.15227/orgsyn.034.0013 |title=Cetylmalonic Ester |journal=Organic Syntheses |date=1954 |volume=34 |page=13|author=Don E. Floyd, Sidney E. Miller }} {{cite journal |doi=10.15227/orgsyn.016.0033 |title=Ethyl Phenylmalonate |journal=Organic Syntheses |date=1936 |volume=16 |page=33|author= P. A. Levene, G. M. Meyer }} {{cite journal |doi=10.15227/orgsyn.026.0042 |title=α-Ketoglutaric Acid |journal=Organic Syntheses |date=1946 |volume=26 |page=42|author=Lester Friedman, Edward Kosower }}
Diethyl oxalate is often used to prepare heterocycles. It is for example a precursor to 3,4-ethylenedioxythiophene.{{cite journal |doi=10.1016/0032-3861(94)90332-8 |title=Electrochromic and Highly Stable Poly(3,4-ethylenedioxythiophene) Switches Between Opaque Blue-Black and Transparent Sky Blue |date=1994 |last1=Pei |first1=Qibing |last2=Zuccarello |first2=Guido |last3=Ahlskog |first3=Markus |last4=Inganäs |first4=Olle |journal=Polymer |volume=35 |issue=7 |pages=1347–1351 }} With urea, it condenses to give parabanic acid.{{cite journal |author=Joseph I. Murray|doi=10.15227/orgsyn.037.0071 |title=Parabanic Acid |journal=Organic Syntheses |date=1957 |volume=37 |page=71 }}