William Standish Knowles – designer of chiral catalysts

William Standish Knowles – designer of chiral catalysts

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & contributions

William Standish Knowles was an American chemist and Nobel laureate born on June 01, 1917 – died on June 13, 2012. Knowles was the receiver of Nobel prize for chirally catalyzed hydrogenation reactions.

Knowles developed one of the first asymmetric hydrogenation catalysts by replacing the achiral triphenylphosphine ligands in Wilkinson's catalyst with chiral phosphine ligands. This experimental catalyst was effective for enantioselective synthesis, achieving a modest 15% enantiomeric excess.

He was also the first to apply enantioselective metal catalysis to industrial-scale synthesis. In the late 1960's, Knowles headed a team seeking to develop a catalyst that could be used to synthesize (make artificially) individual enantiomers of chiral compounds.Knowles helped develop molecules that can catalyze important reactions so that only a desirable pure form without its mirror image is produced.

He made chiral catalysts for a type of reaction called hydrogenation. Knowles's discovery had great significance in chemistry, materials science, biology, and medicine. In particular, his research led to an industrial process for the production of L-3,4-dihydroxyphenylalanine /L-dopa.

Catalysts

Catalysts are nothing but any substance that increases the rate of a reaction without itself being consumed. Estimates indicate that the economic impact of catalytic processing, including pollution abatement, is $10 trillion annually.

Most solid catalysts are metals or the oxides, sulfides, and halides of metallic elements and of the semimetallic elements boron, aluminum, and silicon. Gaseous and liquid catalysts are commonly used in their pure form or in combination with suitable carriers or solvents. Solid catalysts are commonly dispersed in other substances known as catalyst supports.

In general, catalytic action is a chemical reaction between the catalyst and a reactant, forming chemical intermediates that are able to react more readily with each other or with another reactant, to form the desired end product.

Catalysts may affect the reaction environment favorably, or bind to the reagents to polarize bonds, e.g. acid catalysts for reactions of carbonyl compounds, or form specific intermediates that are not produced naturally, such as osmate esters in osmium tetroxide-catalyzed dihydroxylation of alkenes, or cause dissociation of reagents to reactive forms, such as chemisorbed hydrogen in catalytic hydrogenation.

During the reaction between the chemical intermediates and the reactants, the catalyst is regenerated. The modes of reactions between the catalysts and the reactants vary widely and in solid catalysts are often complex.

Catalyzed reactions form the basis of many industrial chemical processes. Catalyst manufacture is itself a rapidly growing industrial process.

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