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Crossover experiments allow for experimental study of a reaction mechanism. Mechanistic studies are of interest to theoretical and experimental chemists for a variety of reasons including prediction of stereochemical outcomes, optimization of reaction conditions for rate and selectivity, and design of improved catalysts for better turnover number, robustness, etc. [6] [7] Since a mechanism ...
A stirred BZ reaction mixture showing changes in color over time. The discovery of the phenomenon is credited to Boris Belousov.In 1951, while trying to find the non-organic analog to the Krebs cycle, he noted that in a mix of potassium bromate, cerium(IV) sulfate, malonic acid, and citric acid in dilute sulfuric acid, the ratio of concentration of the cerium(IV) and cerium(III) ions ...
Several energy sources in planetary atmospheres can induce these dissociation reactions and subsequent hydrogen cyanide or aldehyde formation, including lightning, [32] ultraviolet light, [30] and galactic cosmic rays. [33] For example, here is a set photochemical reactions of species in the Miller-Urey atmosphere that can result in ...
Cascade reactions are often key steps in the efficient total synthesis of complex natural products. The key step in Heathcock's synthesis of dihydroprotodaphniphylline features a highly efficient cascade involving two aldehyde/amine condensations, a Prins-like cyclization, and a 1,5-hydride transfer to afford a pentacyclic structure from an acyclic starting material.
As a general approach, one can simply draw the transition state of the reaction. For a sigmatropic reaction, the transition state will consist of two fragments, joined by the forming and breaking σ-bonds. The sigmatropic reaction is named as a [i,j]-sigmatropic rearrangement (i ≤ j) if these two fragments consist of i and j atoms. This is ...
The Curtin–Hammett principle is a principle in chemical kinetics proposed by David Yarrow Curtin and Louis Plack Hammett.It states that, for a reaction that has a pair of reactive intermediates or reactants that interconvert rapidly (as is usually the case for conformational isomers), each going irreversibly to a different product, the product ratio will depend both on the difference in ...
Nevertheless, some reactions exhibit steric factors greater than unity: the harpoon reactions, which involve atoms that exchange electrons, producing ions. The deviation from unity can have different causes: the molecules are not spherical, so different geometries are possible; not all the kinetic energy is delivered into the right spot; the ...
Small-ring application of the Ramberg–Bäcklund reaction. This reaction type gives access to 1,2-dimethylenecyclohexane. Scheme 5. Ramberg–Bäcklund synthesis of dimethylene-cyclohexane. and the epoxide variation access to allyl alcohols. A recently developed application of the Ramberg–Bäcklund reaction is the synthesis of C-glycosides.