Carbonate ester

A carbonate ester (organic carbonate or organocarbonate) is an ester of carbonic acid. This functional group consists of a carbonyl group flanked by two alkoxy groups. The general structure of these carbonates is R1O(C=O)OR2 and they are related to esters R1O(C=O)R and ethers R1OR2 and also to the inorganic carbonates.

Monomers of polycarbonate (e.g. Lexan) are linked by carbonate groups. These polycarbonates are used in eyeglass lenses, compact discs, and bulletproof glass. Small carbonate esters like dimethyl carbonate, ethylene carbonate, propylene carbonate are used as solvents. Dimethyl carbonate is also a mild methylating agent.

Carbonate ester
Chemical structure of the carbonate ester group.

Types

Carbonate esters can be divided into three categories by their structures. The first and general case is a carbonate group with two simple, identical substituents; depending on whether the substituents are aliphatic or aromatic, they are called dialkyl or diaryl carbonates, respectively. The simplest members of these classes are dimethyl carbonate and diphenyl carbonate. Alternatively, the carbonate groups can be linked by a 2- or 3-carbon bridge, forming cyclic compounds such as ethylene carbonate and trimethylene carbonate. The bridging compound can also have substituents, e.g. CH3 for propylene carbonate. Instead of terminal alkyl or aryl groups, two carbonate groups can be linked by an aliphatic or aromatic bifunctional group. For example, poly(propylene carbonate) and poly(bisphenol A carbonate) (Lexan).

Preparation

There are two main industrial ways of preparing carbonate esters: the reaction of an alcohol (or phenol) with phosgene (phosgenation), and the reaction of an alcohol with carbon monoxide and an oxidizer (oxidative carbonylation). Other carbonate esters may subsequently be prepared by transesterification.[1][2]

In principle carbonate esters can be prepared the direct condensation of methanol and carbon dioxide. The reaction is however thermodynamically unfavorable.[3] A selective membrane can be used to separate the water from the reaction mixture and increase the yield.[4][5][6][7]

Dimethyl carbonate Structural Formulae

Dimethyl carbonate, a representative acyclic carbonate ester

Diphenyl carbonate

Diphenyl carbonate, another representative acyclic carbonate ester

Ethylene carbonate

Ethylene carbonate, a cyclic carbonate ester

Trimethylene carbonate

Trimethylene carbonate, another cyclic carbonate ester

Lexan

Poly(bisphenol A carbonate), a commercially important plastic (Lexan)

Phosgenation

Alcohols react with phosgene to yield carbonate esters according to the following reaction:

2 ROH + COCl2 → RO(CO)OR + 2 HCl

Phenols react similarly. Polycarbonate derived from bisphenol A is produced in this manner. This process is high yielding. However, toxic phosgene is used, and stoichiometric quantities of base (e.g. pyridine) are required to neutralize the hydrogen chloride that is cogenerated.[1][2] Chloroformate esters are intermediates in this process. Rather than reacting with additional alcohol, they may disproportionate to give the desired carbonate diesters and one equivalent of phosgene:[2]

PhOH + COCl2 → PhO(CO)Cl + HCl
2 PhO(CO)Cl → PhO(CO)OPh + COCl2

Overall reaction is:

2 PhOH + COCl2 → PhO(CO)OPh + 2 HCl

Oxidative carbonylation

Oxidative carbonylation is an alternative to phosgenation. The advantage is the avoidance of phosgene. Using copper catalysts, dimethylcarbonate is prepared in this way:[2][8]

2 MeOH + CO + 1/2 O2 → MeO(CO)OMe + H2O

Diphenyl carbonate is also prepared similarly, but using palladium catalysts. The Pd-catalyzed process requires a cocatalyst to reconvert the Pd(0) to Pd(II). Manganese(III) acetylacetonate has been used commercially.[9]

Reaction of carbon dioxide with epoxides

The reaction of carbon dioxide with epoxides is a general route to the preparation of cyclic 5-membered carbonates. Annual production of cyclic carbonates was estimated at 100,000 tonnes per year in 2010.[10] Industrially, ethylene and propylene oxides readily react with carbon dioxide to give ethylene and propylene carbonates (with an appropriate catalyst).[1][2] For example:

C2H4O + CO2 → C2H4O2CO

Catalysts for this reaction have been reviewed, as have non-epoxide routes to these cyclic carbonates.[10] Laboratory methods for the synthesis of carbonate ester involve catalysis by a zinc halide.[11]

Carbonate transesterification

Carbonate esters can be converted to other carbonates by transesterification. A more nucleophilic alcohol will displace a less nucleophilic alcohol. In other words, aliphatic alcohols will displace phenols from aryl carbonates. If the departing alcohol is more volatile, the equilibrium may be driven by distilling that off.[1][2]

From urea with alcohols

Dimethyl carbonate can be made from the reaction of methanol with urea. Ammonia that is produced can be recycled. Effectively ammonia serves as a catalyst for the synthesis of dimethyl carbonate. The byproducts are methyl- and N-methylcarbamate (the latter from the reaction between dimethyl carbonate and methyl carbamate). This process is not an economical.[12]

Uses

Organic carbonates are used as solvents.[13] They are classified as polar solvents and have a wide liquid temperature range. One example is propylene carbonate with melting point −55 °C and boiling point 240 °C. Other advantages are low ecotoxicity and good biodegradability. Many industrial production pathways for carbonates are not green because they rely on phosgene or propylene oxide.[14]

Organic carbonates are used as a solvent in lithium batteries. Due to their high polarity, they dissolve lithium salts. The problem of high viscosity is circumvented by using mixtures for example of dimethyl carbonate, diethyl carbonate, and dimethoxy ethane.

Cyclic carbonates are susceptible to polymerization.

References

  1. ^ a b c d Shaikh, Abbas-Alli G.; Swaminathan Sivaram (1996). "Organic Carbonates". Chemical Reviews. 96 (3): 951–976. doi:10.1021/cr950067i. PMID 11848777.
  2. ^ a b c d e f Hans-Josef Buysch. "Carbonic Esters". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_197.
  3. ^ Zhang, Zhi-Fang (2011). "Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol over CexZr1-xO2and [EMIM]Br/Ce0.5Zr0.5O2". Industrial & Engineering Chemistry Research. 50 (4): 1981–1988. doi:10.1021/ie102017j.
  4. ^ Li, Chuan-Feng (2003). "Study on application of membrane reactor in direct synthesis DMC from CO2 and CH3OH over Cu–KF/MgSiO catalyst". Catalysis Today. 82 (1–4): 83–90. doi:10.1016/S0920-5861(03)00205-0.
  5. ^ http://alexandria.tue.nl/extra1/afstversl/st/vermerris2005.pdf
  6. ^ Aouissi, Ahmed; Al-Othman, Zeid Abdullah; Al-Amro, Amro (2010). "Gas-Phase Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide over Co1.5PW12O40 Keggin-Type Heteropolyanion". International Journal of Molecular Sciences. 11 (4): 1343–1351. doi:10.3390/ijms11041343. PMC 2871119. PMID 20480023.
  7. ^ Bian, Jun (2009). "Highly effective synthesis of dimethyl carbonate from methanol and carbon dioxide using a novel copper–nickel/graphite bimetallic nanocomposite catalyst". Chemical Engineering Journal. 147 (2–3): 287–296. doi:10.1016/j.cej.2008.11.006.
  8. ^ Shaikh, Abbas-Alli G.; Sivaram, Swaminathan (1996-01-01). "Organic Carbonates". Chemical Reviews. 96 (3): 951–976. doi:10.1021/cr950067i. ISSN 0009-2665.
  9. ^ Grigorii L. Soloveichik1 (2016). "Oxidative Carbonylation: Diphenyl Carbonate". In Shannon S. Stahl, andPaul L. Alsters (eds.). Liquid Phase Aerobic Oxidation Catalysis: Industrial Applications and Academic Perspectives. Title Liquid Phase Aerobic Oxidation Catalysis: Industrial Applications and Academic Perspectives: Industrial Applications and Academic Perspectives. Wiley-VCH. pp. 189–208. doi:10.1002/9783527690121.ch12. ISBN 9783527337811.CS1 maint: uses editors parameter (link)
  10. ^ a b North, Michael; Pasquale, Riccardo; Young, Carl (2010). "Synthesis of cyclic carbonates from epoxides and CO2". Green Chem. 12 (9): 1514. doi:10.1039/c0gc00065e.
  11. ^ Zinc(II)-pyridine-2-carboxylate / 1-methyl-imidazole: a binary catalytic system for in the synthesis of cyclic carbonates from carbon dioxide and epoxides Arkivoc 2007 (iii) 151-163 (EA-2262DP) Thomas A. Zevaco, Annette Janssen, and Eckhard Dinjus Link
  12. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2013-10-05. Retrieved 2013-10-04.CS1 maint: archived copy as title (link)
  13. ^ Schäffner, B.; Schäffner, F.; Verevkin, S. P.; Börner, A. (2010). "Organic Carbonates as Solvents in Synthesis and Catalysis". Chemical Reviews. 110 (8): 4554–4581. doi:10.1021/cr900393d. PMID 20345182.
  14. ^ Sibiya, Mike Sbonelo. Catalytic transformation of propylene carbonate into dimethyl carbonate and propylene glycol
3-Hydroxytetrahydrofuran

3-Hydroxytetrahydrofuran (3-OH THF) is a colorless liquid with a normal boiling point of 179 °C and boiling at 88−89 °C at 17 mmHg, with density (1.087 g/cm3 at 19 °C). 3-OH THF is a useful pharmaceutical intermediate. The chiral (absolute configuration S) version of this compound is an intermediate to launched retroviral drugs.

Bacampicillin

Bacampicillin (INN) is a penicillin antibiotic. It is a prodrug of ampicillin with improved oral bioavailability.It is sold under the brand names Spectrobid (Pfizer) and Penglobe (AstraZeneca).

Carbonate

In chemistry, a carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula of CO2−3. The name may also refer to a carbonate ester, an organic compound containing the carbonate group C(=O)(O–)2.

The term is also used as a verb, to describe carbonation: the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by the addition of carbon dioxide gas under pressure, or by dissolving carbonate or bicarbonate salts into the water.

In geology and mineralogy, the term "carbonate" can refer both to carbonate minerals and carbonate rock (which is made of chiefly carbonate minerals), and both are dominated by the carbonate ion, CO2−3. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock. The most common are calcite or calcium carbonate, CaCO3, the chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons); dolomite, a calcium-magnesium carbonate CaMg(CO3)2; and siderite, or iron(II) carbonate, FeCO3, an important iron ore. Sodium carbonate ("soda" or "natron") and potassium carbonate ("potash") have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass. Carbonates are widely used in industry, e.g. in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes, and more.

Cholesteryl oleyl carbonate

Cholesteryl oleyl carbonate (COC) is an organic chemical, a carbonate ester of cholesterol and oleyl alcohol with carbonic acid. It is a liquid crystal material forming cholesteric liquid crystals with helical structure. It is a transparent liquid, or a soft crystalline material with melting point around 20 °C. It can be used with cholesteryl nonanoate and cholesteryl benzoate in some thermochromic liquid crystals.

It is used in some hair colors, make-ups, and some other cosmetic preparations.

It can be also used as a component of the liquid crystals used for liquid crystal displays.

Danishefsky Taxol total synthesis

The Danishefsky Taxol total synthesis in organic chemistry is an important third Taxol synthesis published by the group of Samuel Danishefsky in 1996

two years after the first two efforts described in the Holton Taxol total synthesis and the Nicolaou Taxol total synthesis. Combined they provide a good insight in the application of organic chemistry in total synthesis.

Danishefsky's route to Taxol has many similarities with that of Nicolaou. Both are examples of convergent synthesis with a coupling of the A and the C ring from two precursors. The main characteristic of the Danishefsky variant is the completion of the oxetane D ring onto the cyclohexanol C ring prior to the construction of the 8-membered B ring. The most prominent starting material is the (+) enantiomer of the Wieland-Miescher ketone. This compound is commercially available as a single enantiomer and the single chiral group present in this molecule is able to drive the entire sequence of organic reactions to a single optically active Taxol endproduct. The final step, the tail addition is identical to that of Nicolaou and is based on Ojima chemistry.

In terms of raw material shopping, this taxol molecule consists of the aforementioned Wieland-Miescher ketone, 2-methyl-3-pentanone, lithium aluminium hydride, osmium tetroxide, phenyllithium, pyridinium chlorochromate, the Corey-Chaykovsky reagent and acryloyl chloride. Key chemical transformations are the Johnson-Corey-Chaykovsky reaction and the Heck reaction.

Diethyl carbonate

Diethyl carbonate (sometimes abbreviated DEC) is a carbonate ester of carbonic acid and ethanol with the formula OC(OCH2CH3)2. At room temperature (25 °C) diethyl carbonate is a clear liquid with a low flash point.

Diethyl carbonate is used as a solvent such as in erythromycin intramuscular injections. It can be used as a component of electrolytes in lithium batteries. It has been proposed as a fuel additive to support cleaner diesel fuel combustion because its high boiling point might reduce blended fuels' volatility, minimize vapor buildup in warm weather that can block fuel lines.

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 exempt from the restrictions placed on most volatile organic compounds (VOCs) in the US. Dimethyl carbonate is often considered to be a green reagent.

Diphenyl carbonate

Diphenyl carbonate is the organic compound with the formula (C6H5O)2CO. It is classified as an acyclic carbonate ester. It is a colorless solid. It is both a monomer in combination with bisphenol A in the production of polycarbonate polymers and a product of the decomposition of polycarbonates.

Ethylene carbonate

Ethylene carbonate (sometimes abbreviated EC) is the organic compound with the formula (CH2O)2CO. It is classified as the carbonate ester of ethylene glycol and carbonic acid. At room temperature (25 °C) ethylene carbonate is a transparent crystalline solid, practically odorless and colorless, and somewhat soluble in water. In the liquid state (m.p. 34-37 °C) it is a colorless odorless liquid.

Functional group

In organic chemistry, functional groups are specific substituents or moieties within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of. This allows for systematic prediction of chemical reactions and behavior of chemical compounds and design of chemical syntheses. Furthermore, the reactivity of a functional group can be modified by other functional groups nearby. In organic synthesis, functional group interconversion is one of the basic types of transformations.

Functional groups are groups of one or more atoms of distinctive chemical properties no matter what they are attached to. The atoms of functional groups are linked to each other and to the rest of the molecule by covalent bonds. For repeating units of polymers, functional groups attach to their nonpolar core of carbon atoms and thus add chemical character to carbon chains. Functional groups can also be charged, e.g. in carboxylate salts (–COO−), which turns the molecule into a polyatomic ion or a complex ion. Functional groups binding to a central atom in a coordination complex are called ligands. Complexation and solvation are also caused by specific interactions of functional groups. In the common rule of thumb "like dissolves like", it is the shared or mutually well-interacting functional groups which give rise to solubility. For example, sugar dissolves in water because both share the hydroxyl functional group (–OH) and hydroxyls interact strongly with each other. Plus, when functional groups are more electronegative than atoms they attach to, the functional groups will become polar, and the otherwise nonpolar molecules containing these functional groups become polar and so become soluble in some aqueous environment.

Combining the names of functional groups with the names of the parent alkanes generates what is termed a systematic nomenclature for naming organic compounds. In traditional nomenclature, the first carbon atom after the carbon that attaches to the functional group is called the alpha carbon; the second, beta carbon, the third, gamma carbon, etc. If there is another functional group at a carbon, it may be named with the Greek letter, e.g., the gamma-amine in gamma-aminobutyric acid is on the third carbon of the carbon chain attached to the carboxylic acid group. IUPAC conventions call for numeric labeling of the position, e.g. 4-aminobutanoic acid. In traditional names various qualifiers are used to label isomers, for example, isopropanol (IUPAC name: propan-2-ol) is an isomer of n-propanol (propan-1-ol).

Holton Taxol total synthesis

The Holton Taxol total synthesis, published by Robert A. Holton and his group at Florida State University in 1994 was the first total synthesis of Taxol (generic name: paclitaxel).The Holton Taxol total synthesis is a good example of a linear synthesis starting from commercially available natural compound patchoulene oxide.

This epoxide can be obtained in two steps from the terpene patchoulol and also from borneol. The reaction sequence is also enantioselective, synthesizing (+)-Taxol from (−)-patchoulene oxide or (−)-Taxol from (−)-borneol with a reported specific rotation of +- 47° (c=0.19 / MeOH). The Holton sequence to Taxol is relatively short compared to that of the other groups (46 linear steps from patchoulene oxide). One of the reasons is that patchoulene oxide already contains 15 of the 20 carbon atoms required for the Taxol ABCD ring framework.

Other raw materials required for this synthesis include 4-pentenal, m-chloroperoxybenzoic acid, methyl magnesium bromide and phosgene. Two key chemical transformations in this sequence are a Chan rearrangement and a sulfonyloxaziridine enolate oxidation.

Intramolecular reaction

Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.

Lodenafil

Lodenafil (also known as hydroxyhomosildenafil, trade name Helleva) is a drug belonging to a class of drugs called PDE5 inhibitor, which many other erectile dysfunction drugs such as sildenafil, tadalafil, and vardenafil also belong to. Like udenafil and avanafil it belongs to a new generation of PDE5 inhibitors.

Lodenafil is formulated as a prodrug in the form of the carbonate ester dimer, lodenafil carbonate, which breaks down in the body to form two molecules of the active drug lodenafil. This formulation has higher oral bioavailability than the parent drug.It is manufactured by Cristália Produtos Químicos e Farmacêuticos in Brazil and sold there under the brand-name Helleva.It has undergone Phase III clinical trials, but is not yet approved for use in the United States by the U.S. Food and Drug Administration.

Nicolaou Taxol total synthesis

The Nicolaou Taxol total synthesis, published by K. C. Nicolaou and his group in 1994 concerns the total synthesis of Taxol. Taxol is an important drug in the treatment of cancer but also expensive because the compound is harvested from a scarce resource, namely the pacific yew.

This synthetic route to taxol is one of several; other groups have presented their own solutions, notably the group of Holton with a linear synthesis starting from borneol, the Samuel Danishefsky group starting from the Wieland-Miescher ketone and the Wender group from pinene.

The Nicolaou synthesis is an example of convergent synthesis because the molecule is assembled from three pre-assembled synthons. Two major parts are cyclohexene rings A and C that are connected by two short bridges creating an 8 membered ring in the middle (ring B). The third pre-assembled part is an amide tail. Ring

D is an oxetane ring fused to ring C. Two key chemical transformations are the Shapiro reaction and the pinacol coupling reaction.

The overall synthesis was published in 1995 in a series of four papers.

OMEGA process

The OMEGA process ("Only MEG Advantage") is a process by Shell Global Solutions that is used to produce ethylene glycol from ethylene. This process comprises two steps, the controlled oxidation of ethylene to ethylene oxide, and the net hydrolysis of ethylene oxide to monoethylene glycol (MEG). The first chemical plant using the OMEGA process was started in South Korea. Subsequent OMEGA plants have been started in Saudi Arabia and Singapore. Shell claims that this process, compared to conventional ones, does not produce higher glycols, uses less steam and water, and generates less waste.

Propylene carbonate

Propylene carbonate (often abbreviated PC) is an organic compound with the formula C4H6O3. It is a cyclic carbonate ester derived from propylene glycol. This colorless and odorless liquid is useful as a polar, aprotic solvent. Propylene carbonate is chiral, but is used exclusively as the racemic mixture in most contexts.

Trimethylene carbonate

Trimethylene carbonate or 1,3-propylene carbonate is a 6-membered cyclic carbonate ester. It is a colourless solid that upon heating or catalytic ring-opening converts to the poly(trimethylene carbonate). Such polymers are called aliphatic polycarbonates are of interest for potential biomedical applications. An isomeric derivative is propylene carbonate, a colourless liquid that does not spontaneously polymerize.

Wender Taxol total synthesis

The Wender Taxol total synthesis in organic chemistry describes a Taxol total synthesis (one of six to date) by the group of Paul Wender at Stanford University published in 1997. This synthesis has much in common with the Holton Taxol total synthesis in that it is a linear synthesis starting from a naturally occurring compound with ring construction in the order A,B,C,D. The Wender effort is shorter by approximately 10 steps.

Raw materials for the preparation of Taxol by this route include verbenone, prenyl bromine, allyl bromide, propiolic acid, Gilman reagent, and Eschenmoser's salt.

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