Dipolar effects

However, because of chemical shielding anisotropy (CSA) and quadnipolar and dipolar effects, the Lamior... 

In the case of ionic adsorbates, the variation in WS50is normally unable to provide a clue to the molecular structure of the solvent since free charge contributions outweigh dipolar effects. In this case UHV experiments are able to give a much better resolved molecular picture of the situation. The interface is synthesized by adsorbing ions first and solvent molecules afterward. The variation of work function thus provides evidence for the effect of the two components separately and it is possible to see the different orientation of water molecules around an adsorbed ion.58,86,87 Examples are provided in Fig. 6. 

The corresponding di-n-butyl boron enolate gives the 2,2 -syn adduct. The nonchelating boron is thought to react through a TS in which the conformation of the substituent is controlled by a dipolar effect. 

The other common explanation for the experimental trends in 1-fluoropropenes involves dipolar effects. The dipoles in both isomers are depicted below. 

However, one is unable to predict anything about the rotational barriers in these molecules by considering only the dipolar effect. Consequently, the only rationale capkble of explaining both the geometric as well as the conformational preferences observed appears to be nonbonded attraction. 

A polymeric material, the polymer of the parent compound, was included in the study. The x value is of so small a magnitude that it cannot be determined from the static spectrum (entry 8). The quadrupolar interaction was investigated using MAS in order to measure the x value. Furthermore, when the quadrupolar interaction is of this small size, other interactions have to be considered as well, such as the CSA and dipolar effect from other adjacent lithium cations. 

Multiple-pulse measurements were performed on both the LP and HP samples at 20° and — 80° C, and when no differences were noted, lower temperature measurements were performed only on the LP sample. Multiple-pulse spectra for the LP sample are illustrated in Figure 4 together with the eight-pulse spectrum of the reference used for the low-temperature measurements, Ca(OH)2. The lineshapes observed are quite broad, and the line center is a function of temperature. The line width was separated into three contributions by performing three related multiple-pulse measurements (I). These indicated that the main contributions to the linewidth came from both relaxation and second-order dipolar effects. The maximum possible field inhomogeneity Hamiltonian is estimated to be less than 16 ppm by this means, which indicates that the com-... 

Values of s and s" are calculated using equations in which the contributions of dipolar effects, ionic displacements, and electrode polarization effects are additive. If conduction effects predominate, i.e., when neither interfacial effects nor dipolar effects are significant, the loss factor is given by (Kranbuehl et al., 1986) ... 

That dipolar effect may be substantial is shown by a series of results which agree better with the Cornforth than with the Felkin model.96 Some very interesting results... 

Finally, from a pragmatic point of view, the conductivity is a very sensitive probe of cure. Not only does it become increasingly sensitive to changes in Tg as the end of cure is reached, but it can almost always be measured, even in the presence of dipolar effects, by decreasing the measurement frequency. The conductivity is equally sensitive to small decreases in Tg that result from degradation, a result first noted by Warfield 58). Applications of conductivity measurement to cure studies are reviewed in Section 5. 

Integeninecic acid (36), which occurs as the dilactone in die pyrrolizidine alkaloid integeirimine (33 Scheme 9), was obtained from ketone (34). The observed regioselectivity in die oxidation leading to (35) presumably results from steiic and dipolar effects. ... 

Several different structural factors influence the properties of the mesophase in these polymers, including dipolar effects, the planarity and rigidity of the mesogenic unit, and its length-to-width ratio among others. These factors are difficult to quantify, either absolutely or relatively, but some idea of their influences can be obtained by comparing the properties of polymers with different mesogenic units when combined with the same flexible spacer. This comparison has already been made for the dyad and triad esters in Table 2, and in this section it will be extended to other types of liquid crystalline polymers which contain a common decamethylene spacer. 

For an isolated system there are no external influences so the first term of Equation A4 is zero. The effective pair potential is a function of the pair separation = r, — r jl and is constructed in such a way as to include the true pair potential and average effects of higher order terms it often includes also electrostatic and dipolar effects. The total potential energy of the system is then a sum over all distinct pairs of particles... 

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