Intramolecular interactions, effect motion

The relaxation data for the anomeric protons of the polysaccharides (see Table II) lack utility, inasmuch as the / ,(ns) values are identical within experimental error. Obviously, the distribution of correlation times associated with backbone and side-chain motions, complex patterns of intramolecular interaction, and significant cross-relaxation and cross-correlation effects dramatically lessen the diagnostic potential of these relaxation rates. 

It was shown that the folded conformation is favored by ca. 3 kcal/mcd in enthalpy and the entropy change is 3—4 e.u., vdiich is unfavorable to the folded form. The entropy loss on going to the folded conformation is readfly understandable in terms of the freezing out of all motion of the aromatic side chain in the folded form. The intramolecular interaction is not the process accompanyit the release of bound or ordered solvent molecules (hydroj obic interaction). It seems likely that the folded conformation of the aromatic cyclic dipeptides is stabilized by interaction of amide dipole and aromatic induced-dipole, dispersion forces between polarizable rr systems of the amide group and the aromatic ring, and some sbortHranged, h ily directional effects. As a consequence, the intramolecular interaction is characterized by invariant AH and AS with solvent and it is not destroyed even in amide solvent. 

Temperature dependence of J couplings in the liquid phase may originate in both intramolecular nuclear motions and intermolecular interaction effects. In the review period, experimental and theoretical studies of this dependence were reported. 

It is convenient to discuss the effect of motion on the intramolecular interactions (where r is constant) separately from the intermolecular interactions where both P and r vary with time. Similar transformations of(3 cos Pjh—l) to those employed in the rigid lattice case, enable us to relate the second moment to the angle 7 between the draw direction and Ho, and cos A and cos A which define the orientation functions for the transversely isotropic situation which has been analysed. We find... 

When the solution is dilute, the three diffusion coefficients in Eq. (40a, b) may be calculated only by taking the intramolecular hydrodynamic interaction into account. In what follows, the diffusion coefficients at infinite dilution are signified by the subscript 0 (i.e, D, 0, D10> and Dr0). As the polymer concentration increases, the intermolecular interaction starts to become important to polymer dynamics. The chain incrossability or topological interaction hinders the translational and rotational motions of chains, and slows down the three diffusion processes. These are usually called the entanglement effect on the rotational and transverse diffusions and the jamming effect on the longitudinal diffusion. In solving Eq. (39), these effects are taken into account by use of effective diffusion coefficients as will be discussed in Sect. 6.3. 

Shinkai et al.111-151 synthesized a series of azobis(benzocrown ethers) called butterfly crown ethers , of which compounds 9 and 10 are examples. Their photoresponsive molecular motion resembles that of a flying butterfly. It was found that the proportion of their Z forms at the photostationary state increases remarkably with increasing concentration of Rb+ and Cs+, which interact with two crown rings in a 1 2 sandwich fashion. This is clearly due to the bridge effect of the metal cations with the two crowns, results that support the view that the Z forms make an intramolecular 1 2 complex with these metal cations. As expected, the Z forms extracted alkali metal cations with large ion radii more efficiently than did the corresponding E forms. In particular, the photoirradiation effect on 9 is quite remarkable for example, ( )-9 (n= 2) extracts Na+ 5.6 times more efficiently than (Z)-9 (n= 2), whereas (Z)-9(n= 2) extracts K+ 42.5 times more efficiently than ( )-9(n= 2). l ... 

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