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Hydrogenation is a chemical reaction between molecular hydrogen (H 2) 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 organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule ...
Catalyst deactivation is defined as a loss in catalytic activity and/or selectivity over time. Substances that decrease the reaction rate are called poisons . Poisons chemisorb to the catalyst surface and reduce the number of available active sites for reactant molecules to bind to. [ 22 ]
Transfer hydrogenation catalyzed by transition metal complexes proceeds by an "outer sphere mechanism." The catalytic asymmetric hydrogenation of ketones was demonstrated with ruthenium-based complexes of BINAP. [6] [7] Even though the BINAP-Ru dihalide catalyst could reduce functionalized ketones, the hydrogenation of simple ketones remained ...
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity.Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction.
For instance, in the hydrogenation of alkynes to alkenes, a palladium (Pd) catalyst partly "poisoned" with lead(II) acetate (Pb(CH 3 CO 2) 2) can be used (Lindlar catalyst). [48] Without the deactivation of the catalyst, the alkene produced would be further hydrogenated to alkane .
In chemistry, homogeneous catalysis is catalysis where the catalyst is in same phase as reactants, principally by a soluble catalyst in a solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid and gas, respectively. [1]
The Guerbet reaction, reported in 1899, [5] is an early example of a hydrogen auto-transfer process. The Guerbet reaction converts primary alcohols to β-alkylated dimers via alcohol dehydrogenation followed by aldol condensation and reduction of the resulting enones.
In acid catalysis and base catalysis, a chemical reaction is catalyzed by an acid or a base. By Brønsted–Lowry acid–base theory, the acid is the proton (hydrogen ion, H +) donor and the base is the proton acceptor. Typical reactions catalyzed by proton transfer are esterifications and aldol reactions.