NationMaster - Encyclopedia: Transfer hydrogenation

Transfer hydrogenation is the addition of hydrogen (H₂; dihydrogen in inorganic and organometallic chemistry) to a molecule from a source other than gaseous H₂. Transfer hydrogenation is applied in industry and in organic synthesis, in part because of the inconvenience and expense of using gaseous H₂. One large scale application of transfer hydrogenation is coal liquifaction using "donor solvents" such as tetralin.^[1] This article is about the chemistry of hydrogen. ... Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ... It has been suggested that Organometallic compounds be merged into this article or section. ... In chemistry, a molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds [1] [2] [3] [4] [5]. Chemical substances are not infinitely divisible into smaller fractions of the same substance: a molecule is generally considered the smallest particle of a pure... Organic synthesis is the construction of organic molecules via chemical processes. ... The chemical structure of tetralin Tetralin is a hydrocarbon having the chemical formula C10H12. ...

In the area of organic synthesis, a useful family of hydrogen-transfer catalysts have been developed based on ruthenium and rhodium diamine and phosphine complexes.^[2] These catalysts are mainly employed for the reduction of ketones and imines to alcohols and amines, respectively. The hydrogen-donor (transfer agent) is typically isopropanol, which coverts to acetone upon donation of hydrogen. Transfer hydrogenations can proceed with high enantioselectivities when the starting material is chiral: Organic synthesis is the construction of organic molecules via chemical processes. ... Phosphine is the common name for phosphorus hydride (PH3), also known by the IUPAC name phosphane and, occasionally, phosphamine. ... Isopropyl alcohol or isopropanol is a common name for 2-propanol, an alcohol commonly used for application to the skin, and popularly referred to as rubbing alcohol. ... In chemistry, acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and Î²-ketopropane) is the simplest representative of the ketones. ...

RR'C=O + Me₂CHOH → RR'C*H-OH + Me₂C=O

where RR'C*H-OH is a chiral product. A typical catalyst is (arene)Ru(R,R-HNCHPhCHPhNTs), where Ts = SO₂C₆H₄Me and R,R refers to the absolute configuration of the two chiral carbon centers. This work was recognized with the 2001 Nobel Prize in Chemistry to Ryoji Noyori. Arene or Ar means several things: Another term for aromatic hydrocarbon In Greek mythology, Arene was the wife of Aphareus and mother of Idas and Lynceus. ... An absolute configuration in stereochemistry is the spatial arrangement of the atoms of a chiral molecular entity (or group)and its stereochemical description e. ... Ryoji Noyori (é‡Žä¾è‰¯æ²») (born September 3, 1938) won the Nobel Prize in Chemistry in 2001. ...

Another family of hydrogen-transfer agents are those based on aluminium alkoxides, such as Aluminium isopropoxide. Aluminium isopropoxide is an inorganic compound and the adduct of aluminum and isopropyl alcohol. ...

A historically prominent transfer hydrogenation agent is diimide, which becomes oxidized to N₂. In chemistry, azo compounds generally have a molecular formula of the form R-N=N-R, in which R and R can be either aromatic or aliphatic. ...

Half of the hydrogen in the hydrazine is transferred to the substrate. The reaction produces the very stable molecule N₂ molecule. Hydrazine is the chemical compound with formula N2H4. ...

Another similar example of the use of transfer hydrogenation where the product is an alkane is when the hydrogen supplier is cyclohexane. In this case an alkane is formed along with the formation of benzene. The driving force of the reaction being the gain of aromatic stabilization energy when benzene is formed. Pd can be used as a catalyst and a temperature of 100 °C is employed.

One limitation of using transfer hydrogenation for the production of alkane is that it cannot be used to prepare methane as no unsaturated hydrocarbon contain only one carbon.

More exotic transfer hydrogenations have been reported, including this intramolecular one:

References

^ Speight, J. G. "The Chemistry and Technology of Coal" Marcel Dekker; New York, 1983; p. 226 ff. ISBN 0-8247-1915-8.
^ T. Ikariya, K. Murata, R. Noyori "Bifunctional Transition Metal-Based Molecular Catalysts for Asymmetric Syntheses" Org. Biomol. Chem., 2006, volume 4, 393-406.

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