Lewis Proposed working model

Fig. 1.2 Proposed working model of Lewis acid-Lewis acid cooperative catalysis using YLB (13).

From analogy with the cyanosilylation of aldehydes a working model for the catalytic cycle has been proposed in which the Lewis acid (Al) and the Lewis base (phosphine oxide) activate the imine and TMSCN respectively. 

In 1920, two men in G.N. Lewis laboratory at Berkeley proposed the hydrogen bond (Latimer and Rodebush, 1920) using a simplified electrostatic point charge model of the water molecule. The work by Kollman (1977) indicated that the simplified model remains acceptable because of a cancellation of two other energy components. 

Obviously, such interpetation led to disregard advanced solutions as nonphysical. For instance, Ritz [30] and Tetrode [31] considered that the mathematical existence of advanced solutions was a major weakness of Maxwell s equations. An attempt to provide a physical basis for advanced potentials is due to Lewis, who proposed focusing on the process of propagation from an emitter to an absorber far away from the emitter [32]. This concept also appears in the work of Wheeler and Feynman [33]. However, such model constitutes another form of causality violation. Lewis [32, p. 25] himself stated I shall not attempt to conceal the conflict between these views and common sense. ... 

Much work has been done to characterize surface and catalytic properties of Si02—A1203 and other mixed-oxide systems. It is well known from these studies that Si02—A1203 possesses Lewis as well as Br nsted acid sites that are interconvertible. Different models for the site structures have been proposed. Tanabe 20) has recently reviewed these attempts to characterize the surfaces of silica-alumina mixed oxides as well as those of crystalline silica-aluminas. 

Retention of Rohrschneider-McReynolds standards of selected chiral alcohols and ketones was measured to determine the thermodynamic selectivity parameters of stationary phases containing (- -)-61 (M = Pr, Eu, Dy, Er, Yb, n = 3, R = Mef) dissolved in poly(dimethylsiloxane) . Separation of selected racemic alcohols and ketones was achieved and the determined values of thermodynamic enantioselectivity were correlated with the molecular structure of the solutes studied. The decrease of the ionic radius of lanthanides induces greater increase of complexation efficiency for the alcohols than for the ketone coordination complexes. The selectivity of the studied stationary phases follows a common trend which is rationalized in terms of opposing electronic and steric effects of the Lewis acid-base interactions between the selected alcohols, ketones and lanthanide chelates. The retention of over fifty solutes on five stationary phases containing 61 (M = Pr, Eu, Dy, Er, Yb, n = 3, R = Mef) dissolved in polydimethylsiloxane were later measured ". The initial motivation for this work was to explore the utility of a solvation parameter model proposed and developed by Abraham and coworkers for complexing stationary phases containing metal coordination centers. Linear solvation... 

Langmuir, Irving (1881-1957) American chemist. In 1919 Langmuir extended the model of electrons in atoms proposed by Gilbert lewis to try to account for the chemical valence of all atoms. In the 1920s he investigated the chemistry of surfaces very extensively. He won the 1932 Nobel Prize for chemistry for his work on chemical reactions at surfaces. 

Recently, hydrocyanation and cyanosilylation reactions with other type of chiral aluminum complexes were reported. In 1999, Shibasaki and Kanai reported enantioselective cyanosilylation of aldehydes catalyzed by Lewis acid-Lewis base bifunctional catalyst (64a) [56, 57]. In this catalyst, aluminum center works as a Lewis acid to activate the carbonyl group, and the oxygen atom of the phosphine oxide works as a Lewis base to activate TMSCN. Asymmetric induction was explained by the proposed transition state model having the external phosphine oxide coordination to aluminum center, thus giving rise to pentavalent aluminum... 

Following the classical works of Archard (6), and later Ratner and coworkers (12) and Lancaster (9), on modeling of the wear rate for materials and in particular polymer, several researchers have tried to present new wear models. These models are mainly based upon the notion that irrespective of the contact deformational mode, the wear rate must be dependent and hence proportional to some combination of bulk mechanical properties, operational parameters, and the initial counterface conditions. These models have essentially tried to empirically fit some experimental data and hence they can be applied to the very specific systems where they have been derived from. Works by Lewis (19), Kar and Bahadur (20), Rhee (21), and Wang and co-workers (22) may be cited here, and a list of these wear models are listed in Table 1 together with the models proposed by Archard (6), Ratner and co-workers (12), and Hollander and Lancaster (15). 

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