Mechanism Molecular Factors

Quantum mechanical/molecular mechanical study on the Favorskii rearrangement in aqueous media has been carried out.39 The results obtained by QM/MM methods show that, of the two accepted mechanisms for Favorskii rearrangement, the semibenzilic acid mechanism (a) is favored over the cyclopropanone mechanism (b) for the a-chlorocyclobutanone system (Scheme 6.2). However, the study of the ring-size effects reveals that the cyclopropanone mechanism is the energetically preferred reactive channel for the a-chlorocyclohexanone ring, probably due to the straining effects on bicycle cyclopropanone, an intermediate that does not appear on the semibenzilic acid pathway. These results provide new information on the key factors responsible for the behavior of reactant systems embedded in aqueous media. 

In addition to the structural and molecular factors listed above, the following environmental or external variables are important in determining mechanical behavior ... 

Table 1 Molecular factors governing the dichotomy between concerted and stepwise mechanisms...

TABLE 3.2. Molecular Factors Governing the Dichotomy Between Concerted and Stepwise Mechanisms... 

Whereas the quantum-mechanical molecular Hamiltonian is indeed spherically symmetrical, a simplified virial theorem should apply at the molecular level. However, when applied under the Born-Oppenheimer approximation, which assumes a rigid non-spherical nuclear framework, the virial theorem has no validity at all. No amount of correction factors can overcome this problem. All efforts to analyze the stability of classically structured molecules in terms of cleverly modified virial schemes are a waste of time. This stipulation embraces the bulk of modern bonding theories. 

When gas molecules hit a solid surface, they may be either reflected, or captured by the surface field of force and condense, to evaporate again later. In Langmuir s adsorption theory the factor a expresses the fraction of the impinging molecules which do condense on the surface. In recent years much information as to the manner of reflection or condensation has been obtained experimentally by the use of molecular rays, and theoretically by wave mechanics. Molecular rays are beams of molecules on which a particular direction has been imposed by slits, moving in a vacuum so high that there are practically no collisions between molecules, and the direction of the beams is maintained for long distances. 

A linear relationship exists between the toughness (integrated stress-strain curve) and the dynamic mechanical dissipation factor. The types of materials that fit this relationship include glassy polymers, elastomers, and an impregnated fabric. The existence of this relationship indicates that toughness arises from the molecular motions which give rise to the dynamic mechanical properties. 

De Flora S, Izzotti A (2007) Mutagenesis and cardiovascular diseases molecular mechanisms, risk factors, and protective factors. Mutat Res 621(l-2) 5-17... 

In contrast to common belief, compaction/granulation is well suited for the manufacturing of easily degradable carrier particles since one of the main binding mechanism, molecular forces (van-der-Waals), diminishes by a factor of 10 in the presence of water. Therefore, if rain or dew wet the granules they lose strength, readily degrade, and liberate the active substance. 

The polystyrene data provide evidence tiiat a cyclic intermediate is involved as part of the chain-breaking mechanism. If one assumes that the kinetics of polymerization and depolymerization are the same, and that solution and gas-phase kinetics are governed by the same molecular factors, then one can apply the relationship ... 

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