Isotope Effects, Dynamic Matching, and Solvent Dynamics in a Wittig Reaction. Betaines as Bypassed Intermediates

Isotope Effects, Dynamic Matching, and Solvent Dynamics in a Wittig Reaction. Betaines as Bypassed Intermediates

The mechanism of the Wittig reaction of anisaldehyde with a stabilized ylide was studied by a combination of (13)C kinetic isotope effects, conventional calculations, and molecular dynamics calculations in a cluster of 53 THF molecules. The isotope effects support a cycloaddition mechanism involving two sequential transition states associated with separate C-C and P-O bond formations. However, ...

Solvent isotope effects on the glucokinase reaction

The solvent isotope effects on the reaction catalysed by rat-liver glucokinase have been studied. At low concentrations of glucose and high concentrations of MgATP2there is an inverse solvent isotope effect of 3.5. At high glucose concentrations there is a normal solvent isotope effect of 1.3. In 'HzO there is positive co-operativity with respect to glucose [Storer, A. C. and Cornish-Bowden, A....

critical period effects in foreign language learning:the influence of maturational state on the acquisition of reading,writing, and grammar in english as a foreign language

since the 1960s the age effects on learning both first and second language have been explored by many linguists and applied linguists (e.g lennerberg, 1967; schachter, 1996; long, 1990) and the existence of critical period for language acquisition was found to be a common ground of all these studies. in spite of some common findings, some issues about the impacts of age on acquiring a second or...

Solvent polarization and kinetic isotope effects in nitroethane deprotonation and implications to the nitroalkane oxidase reaction.

We have carried out a mixed molecular dynamics and centroid path integral simulation using a combined quantum mechanical and molecular mechanical (QM/MM) potential to study the anomalous Brønsted relationship between rates and equilibria for deprotonation of nitroalkanes in water, which is known as the nitroalkane anomaly. The deprotonation process is catalyzed by nitroalkane oxidase. Our resul...

The Wittig Reaction