Dimethyl Oxalate on:
[Wikipedia]
[Google]
[Amazon]
Dimethyl oxalate is the
''Oxidative Carbonylation of Alkanols Catalyzed by Pd(II)-Phosphine Complexes''
PhD Thesis, Ca’Foscari University Venice, 2009 The synthesis gas is mostly obtained from
In the next step of dicarbonylation (3) 
The sum equation:
:
This method is lossless with respect to methyl nitrite, which acts practically as a carrier of oxidation equivalents. However, the water formed must be removed to prevent hydrolysis of the dimethyl oxalate product. With 1% Pd/α-Al2O3 dimethyl oxalate is produced selectively in a dicarbonylation reaction, under the same conditions with 2% Pd/C dimethyl carbonate is produced by monocarbonylation:
:
Alternatively, the oxidative carbonylation of methanol can be carried out with high yield and selectivity with 
The methanol formed is recycled in the process of oxidative carbonylation. Other plants with a total annual capacity of more than 1 million tons of ethylene glycol per year are planned.
Decarbonylation gives 
Diphenyl oxalate is obtained by 
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
with the formula (CO2CH3)2. It is the dimethyl ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
of oxalic acid
Oxalic acid is an organic acid with the systematic name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early inve ...
. Dimethyl oxalate is a colorless or white solid that is soluble in water.
Production
Dimethyl oxalate can be obtained byesterification
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
of oxalic acid with methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
using sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
as a catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
:
:
Oxidative carbonylation route
The preparation byoxidative carbonylation Oxidative carbonylation is a class of reactions that use carbon monoxide in combination with an oxidant to generate esters and carbonate esters. These transformations utilize transition metal complexes as homogeneous catalysts. Many of these reac ...
has attracted interest because it requires only C1 precursors:
:
The reaction is catalyzed by Pd2+.E. Amadio''Oxidative Carbonylation of Alkanols Catalyzed by Pd(II)-Phosphine Complexes''
PhD Thesis, Ca’Foscari University Venice, 2009 The synthesis gas is mostly obtained from
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
or biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
. The oxidation proceeds via dinitrogen trioxide
Dinitrogen trioxide is the chemical compound with the formula N2O3. It is one of the simple nitrogen oxides. It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21 °C (−6 °F):
:NO ...
, which is formed according to (1) of nitrogen monoxide
Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its c ...
and oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
and then reacts according to (2) with methanol forming methyl nitrite
Methyl nitrite is an organic compound with the chemical formula . It is a gas, and is the simplest alkyl nitrite.
Structure
At room temperature, methyl nitrite exists as a mixture of ''cis'' and ''trans'' conformers. The ''cis'' conformer is ...
:X.-Z. Jiang, ''Palladium Supported Catalysts in CO + RONO Reactions'', Platinum Metals Rev., 1990, 34, (4), 178–180
:
In the next step of dicarbonylation (3) carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
reacts with methyl nitrite to dimethyl oxalate in the vapor phase at atmospheric pressure and temperatures at 80-120 °C over a palladium
Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...
catalyst:
:
The sum equation:
:
This method is lossless with respect to methyl nitrite, which acts practically as a carrier of oxidation equivalents. However, the water formed must be removed to prevent hydrolysis of the dimethyl oxalate product. With 1% Pd/α-Al2O3 dimethyl oxalate is produced selectively in a dicarbonylation reaction, under the same conditions with 2% Pd/C dimethyl carbonate is produced by monocarbonylation:
:
Alternatively, the oxidative carbonylation of methanol can be carried out with high yield and selectivity with 1,4-benzoquinone
1,4-Benzoquinone, commonly known as ''para''-quinone, is a chemical compound with the formula C6H4O2. In a pure state, it forms bright-yellow crystals with a characteristic irritating odor, resembling that of chlorine, bleach, and hot plastic o ...
as an oxidant in the system Pd(OAc)2/ PPh3/benzoquinone with mass ratio 1/3/100 at 65 °C and 70 atm CO:
:
Reactions
Dimethyl oxalate (and the related diethyl ester) is used in diversecondensation reaction
In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...
s. For example, diethyl oxalate condenses with cyclohexanone
Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid has an odor reminiscent of acetone. Over time, samples of cyclohexan ...
to give the diketo-ester, a precursor to pimelic acid. With diamines, the diesters of oxalic acid condense to give cyclic diamides. Quinoxalinedione
Quinoxalinedione is an organic compound with the formula C6H4(NH)2(CO)2. It is a colorless solid that is soluble in polar organic solvents. Quinoxalinediones are a family of related compounds sharing the same bicyclic core. Various quinoxalinedi ...
is produced by condensation of dimethyloxalate and o-phenylenediamine
''o''-Phenylenediamine (OPD) is an organic compound with the formula C6H4(NH2)2. This aromatic diamine is an important precursor to many heterocyclic compounds. It is isomeric with ''m''-phenylenediamine and ''p''-phenylenediamine.
Preparation ...
:
:C2O2(OMe)2 + C6H4(NH2)2 → C6H4(NHCO)2 + 2 MeOH
Hydrogenation gives ethylene glycol
Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...
. Dimethyl oxalate can be converted into ethylene glycol in high yields (94.7%)
:
The methanol formed is recycled in the process of oxidative carbonylation. Other plants with a total annual capacity of more than 1 million tons of ethylene glycol per year are planned.
Decarbonylation gives dimethyl carbonate
Dimethyl carbonate (DMC) is an organic compound with the formula OC(OCH3)2. It is a colourless, flammable liquid. It is classified as a carbonate ester. This compound has found use as a methylating agent and more recently as a solvent that is ...
.
:
Diphenyl oxalate is obtained by transesterification
In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction can ...
with phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it req ...
in the presence of titanium catalysts, which is again decarbonylated to diphenyl carbonate in the liquid or gas phase.
Dimethyl oxalate can also be used as a methylating agent
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...
. It is notably less toxic than other methylating agents such as methyl iodide
Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one h ...
or dimethyl sulfate
Dimethyl sulfate (DMS) is a chemical compound with formula (CH3O)2SO2. As the diester of methanol and sulfuric acid, its formula is often written as ( CH3)2 SO4 or Me2SO4, where CH3 or Me is methyl. Me2SO4 is mainly used as a methylating agent ...
.
References
{{Reflist Oxalate esters Methyl esters