The Reichstein process in chemistry is a combined

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wit ...

and microbial method for the production of

ascorbic acid Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) a ...

from D-glucose that takes place in several steps. This process was devised by

Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfre ...

winner Tadeusz Reichstein and his colleagues in 1933 while working in the laboratory of the ETH in

Zürich , neighboring_municipalities = Adliswil, Dübendorf, Fällanden, Kilchberg, Maur, Oberengstringen, Opfikon, Regensdorf, Rümlang, Schlieren, Stallikon, Uitikon, Urdorf, Wallisellen, Zollikon , twintowns = Kunming, San Francisco Zürich () i ...

Reaction steps

The reaction steps are: *

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate org ...

of D-

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...

to D- sorbitol, an organic reaction with

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

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 ...

under high temperature and high pressure. * Microbial

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

or fermentation of sorbitol to L- sorbose with acetobacter at pH 4-6 and 30 °C. * protection of the 4

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydrox ...

groups in sorbose by formation of the acetal with

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscible wi ...

and an acid to Diacetone-L-sorbose (2,3:4,6−Diisopropyliden−α−L−sorbose) * Organic oxidation with

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

(to

Diprogulic acid Diprogulic acid (also known as dikegulac) is a precursor used in commercial ascorbic acid production. In agriculture, its sodium salt, dikegulac sodium, is used as a plant growth regulator, primarily used as a branching agent. When it is taken u ...

) followed by heating with water gives the 2-Keto-L-gulonic acid * The final step is a ring-closing step or gamma lactonization with removal of water. * Intermediate 5 can also be prepared directly from 3 with

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 we ...

and

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...

: The microbial oxidation of sorbitol to sorbose is important because it provides the correct

stereochemistry Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereo ...

Importance

This process was patented and sold to

Hoffmann-La Roche F. Hoffmann-La Roche AG, commonly known as Roche, is a Swiss multinational healthcare company that operates worldwide under two divisions: Pharmaceuticals and Diagnostics. Its holding company, Roche Holding AG, has shares listed on the SIX ...

in 1934. The first commercially sold vitamin C product was either ''Cebion'' from Merck or Redoxon from Hoffmann-La Roche. Even today industrial methods for the production of ascorbic acid can be based on the Reichstein process. In modern methods however, sorbose is directly oxidized with a platinum catalyst (developed by

Kurt Heyns Kurt is a male given name of Germanic or Turkish origin. ''Kurt'' or ''Curt'' originated as short forms of the Germanic Conrad, depending on geographical usage, with meanings including counselor or advisor. In Turkish, Kurt means "Wolf" and is ...

(1908–2005) in 1942). This method avoids the use of protective groups. A side product with particular modification is 5-Keto-D-gluconic acid. A shorter biotechnological synthesis of ascorbic acid was announced in 1988 by

Genencor International Genencor is a biotechnology company based in Palo Alto, CA and a subsidiary of IFF. Genencor is a producer of Industrial enzymes and low-priced bulk protein. The name Genencor originates with Genencor, Inc., the original joint venture between G ...

and Eastman Chemical. Glucose is converted to 2-keto-L-gulonic acid in two steps (via 2,4-diketo-L-gulonic acid intermediate) as compared to five steps in the traditional process. Though many organisms synthesize their own vitamin C, the steps can be different in plants and mammals. Smirnoff concluded that “..little is known about many of the enzymes involved in ascorbate biosynthesis or about the factors controlling flux through the pathways". There is interest in finding alternatives to the Reichstein process. Experiments suggest that genetically modified bacteria might be commercially usable.Hancock, Robert D. und Viola, Roberto. (2002): ''Biotechnological approaches for L-ascorbic acid production''. In: ''Trends in Biotechnology'' 20(7); S. 299–305; ;

References

Literature

* Boudrant, J. (1990): ''Microbial processes for ascorbic acid biosynthesis: a review''. In: ''Enzyme Microb Technol. 12(5); 322–9; ; * Bremus, C. ''et al.'' (2006): ''The use of microorganisms in L-ascorbic acid production''. In: ''J Biotechnol.'' 124(1); 196–205; ;

External links

* http://www.chemieunterricht.de/dc2/asch2/a-synthe.htm
Der Schweizerische Weg zur Viamin-C-Synthese
{{DEFAULTSORT:Reichstein Process Organic reactions