Search results
Results From The WOW.Com Content Network
Referred to as asymmetric depletion, a negative non-linear effect is present when the ee product is lower than predicted by an ideal linear situation. [3] In contrast to a (+)-NLE, a (−)-NLE results in a faster overall reaction rate and a decrease in enantioselectivity.
Kinetic resolution is a possible method for irreversibly differentiating a pair of enantiomers due to (potentially) different activation energies. While both enantiomers are at the same Gibbs free energy level by definition, and the products of the reaction with both enantiomers are also at equal levels, the Δ G ‡ {\displaystyle \Delta G ...
Asymmetric synthesis has become a much explored field due to the challenge of creating a compound with a single 3D structure. [1] Even more challenging is the ability to take a racemic mixture and have only one chiral product left after a reaction. One method that has become an exceedingly useful tool is dynamic kinetic resolution (DKR).
Enantioselective synthesis, also called asymmetric synthesis, [1] is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric ( enantiomeric or diastereomeric ) products in unequal ...
K. Barry Sharpless was the first to develop a general, reliable enantioselective alkene dihydroxylation, referred to as the Sharpless asymmetric dihydroxylation (SAD). Low levels of OsO 4 are combined with a stoichiometric ferricyanide oxidant in the presence of chiral nitrogenous ligands to create an asymmetric environment around the oxidant.
Asymmetric hydrogenation methods using iron have been realized, although in terms of rates and selectivity, they are inferior to catalysts based on precious metals. [19] In some cases, structurally ill-defined nanoparticles have proven to be the active species in situ and the modest selectivity observed may result from their uncontrolled ...
Asymmetric counteranion directed catalysis (ACDC) [1] or chiral anion catalysis [2] in enantioselective synthesis is the "induction of enantioselectivity in a reaction proceeding through a cationic intermediate by means of ion pairing with a chiral, enantiomerically pure anion provided by the catalyst". [1]
Asymmetric autocatalysis occurs when the reaction product is chiral and thus serves as a catalyst for its own production. Reactions of this type, such as the Soai reaction , have the property that they can amplify a very small enantiomeric excess into a large one. [ 8 ]