Long-range asymmetric interactions

Long-range asymmetric induction controlled by supramolecular interaction of intermediate dilithio species (60) has been shown to account for the selective formation of two (out of four) /(-hydroxy sulfone diastereoisomers on reaction of a-sulfonyl carbanions with benzaldehyde in THF at — 100°C.58... 

A new, metal-free protocol involving (heteroaryl)oxazoline catalysts for the enantioselective reduction of aromatic ketones (up to 94% ee) and ketimines (up to 87% ee) with trichlorosilane has been developed. The reaction is characterized by an unusual, long-ranging chiral induction.The enantiodifferentiation is presumed to be aided by aromatic interactions between the catalyst and the substrate.360 Asymmetric reduction of A-arylketimines with trichlorosilane is catalysed by A-methyl-L-amino acid-derived Lewis-basic organocatalysts with high enantioselectivity (up to 92% ee) 61... 

Figure 4.9. Density of states of the naphthalene Nhg triplet excitonic band. We note the asymmetric form due to the coexistence of equivalent and nonequivalent interactions, and the three van Hove points connected with the long-range order two discontinuities at the boundaries (at — 3.S and 5.8 cm1) ane one logarithmic divergence (at —1cm"1), characteristic of 2D dispersion. The optical absorption occurs at the two ends of the band (the a and b Davydov components).

Exceptions to this statement are found in polymers with asymmetric monomer units coupled head-to-tail, such as cellulose derivatives [Scherer. Levi and Hawkins (224 ) Scherer, Tanenbaum and Levi (225) Kheir (137 )], polypeptides [Wada (259 )] and polypropylene oxides [Baur (336)]. In general, the -dipole moment is free of the effects of long-range interactions only if the correlation (jj, L vanishes, where p is the dipole moment vector and L is the end-to-end vector. 

In mesopores a multilayer film will be adsorbed at the pore wall as the saturation pressure is approached. The stability of this film is determined by the interaction with the wall, e.g. long-range Van der Waals Interaction, and by the surface tension and curvature of the liquid-vapour interface. Saam and Cole -have advanced a theory, showing how the curved film becomes unstable at a certain critical thickness t = a-r. The adsorption process is shown schematically in fig. 1.32a (1) (3). During desorption (4) -> (6) an asymmetrical state... 

It is expected that a similar physical picture also holds for interacting PE stars. At distances between core domains 2d > 2R, the star coronae would start to contract due to the overlap of ionic atmospheres. As a result, the stars would become asymmetric and remain separated by a water layer in a range of distances 2d < 2R. The long-range interactions due to the overlap of ionic atmospheres are essential for PE stars with a moderate number of arms (typical for experimental systems), and at low ionic strength in the solution [27],... 

Dynamical aspects of Q2D suspensions of spherical colloids and asymmetric colloid mixtures with long-range repulsive forces have been investigated by Brownian dynamics simulations [193-195]. These works emphasize dynamic scaling and the importance of hydrodynamic interactions on self- and tracer diffusion. 

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