Corey model

Figure 8 Sharpless and Corey models for the enantiodifferentiating step in dihydroxylation.

To use Equation 6.4, one must measure or calculate hc dr for a given aquifer material. A mathematical formula for the water pressure-saturation curve during drainage is needed to calculate the average water pressure head. The Brooks-Corey model of the drainage curve can be used as follows (Corey, 1986) ... 

The Corey model Figure 17. The proposed transition-state models. 

Figure 3.3 The U-shaped (Corey model) and L-shaped (Sharpless model) binding pockets.

The Corey model, presented in Scheme 10, is based on the formation of an osmium tetroxide-chiral ligand ternary complex through a rapid and reversible equilibrium. Inside this complex, the osmium tetroxide is added to the alkene via a (3-1-2) addition mechanism forming the ligand-bound osmium (VI) glyco-late complex. 

The Corey mechanistic proposal is founded on the ability of the alkene substrate to bind between the two quinohne ring walls which are spaced parallel with a separation of 7.2 A. When the substrate binds in this elongated cleft, the alkene complexes to the osmium center in the W-complexated osmium tetroxide through a donor-acceptor (d-Jt) interaction (Scheme 10). The interaction between the alkene and osmium tetroxide is also complemented with favorable van der Waals interactions between the alkene and the binding cleft. These interactions are implied by the Michaelis-Menten kinetics [72] observed in the process. The observation of Michaelis-Menten kinetics in the AD process has however been questioned as an experimental artifact by the Sharpless group [73]. The (3+2) addition takes place between the axial and one of the equatorial oxygen atoms in osmium tetroxide which are in close proximity with the alkene. This represents the minimum motion pathway in the formation of the pentacoordinate os-mium(VI) glycolate ester. In the Corey model the rate acceleration observed in... 

One of the advantages with the Corey model is the heuristic value incorporated in this simple transition state model, where ligand modifications open the possibility of increasing and changing the selectivity for certain substrates. One of these is exemplified below, the others which are represented in enhanced selectivity in the AD of allyhc 4-methoxybenzoates [75] and increased selectivity for terminal dihydroxylation of polyenes [46], can be found in the literature [44]. 

Tetrahedral Corey model for Diels-Alder addition... 

The three-dimensional structure of DNA was reported in a landmark paper by James Watson and Francis Crick in 1953 [11]. As in the determination of protein structure, certain experimental X-ray diffraction data indicated that the overall structure was helical. Earlier that same year, Linus Pauling and Robert Corey published a proposed structure for DNA that was composed of three intertwined chains [12]. Unlike the Pauling-Corey model, the Watson-Crick intertwined "double... 

The Thomeer model is similar to the Brooks-Corey model. The difference between the two is the definition of the normalized saturation. 

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