Influencing factors resonance contributions

The observations that azide A reacts twice as fast as B, which in turn reacts faster than C, are consistent with the proposed mechanism, and may be attributed to steric factors (R1 = H, CHj, or f-Bu). Similarly, the much faster reaction of D over A and the failure of E to undergo addition have also been rationalized on the basis of the changing nucleophilicity at the / carbon as influenced by resonance contributions from the para substituents of the phenyl group in the a position.6 The reaction mechanism is analogous to the... 

The great advantage of the bottom-up approach to measurement uncertainty, even if precision data are to be used extensively, is that the analyst is made to consider the experiment in detail and he or she must understand the analysis and components of vmcertainty. This may provide a useful insight into possible improvements that could be made to lower the combined uncertainty. Influence factors that are estimated to contribute less than, say, 20% to the measurement uncertainty can really be ignored when finding aspects for improvement. The contributions to measurement uncertainty can be displayed on a Pareto chart, which shows the individual components and cumulative effect. An example for a quantitative nuclear magnetic resonance (NMR) study is shown in Figure 4. 

In the aromatic-ring-annelated oxepin series the resonance effect is clearly the major influence dominating other factors (e.g. temperature, solvent, etc.) which affect the oxepin-arene oxide equilibrium. It is however very difficult to exclude the presence of a minor (spectroscopically undetectable) contribution from either tautomer at equilibrium. This problem has been investigated by the synthesis of chiral arene oxides from polycyclic aromatic hydrocarbons (PAHs). The presence of oxepin (26) in equilibrium with naphthalene 1,2-oxide has been excluded by the synthesis of the optically active arene oxide which showed no evidence of racemization in solution at ambient temperature via the achiral oxepin (26) <79JCS(Pl)2437>. 

A DSP analysis, in which contributions due to inductive and resonance effects of substituents are considered separately, has been applied in order to obtain a deeper level of insight into the electronic factors influencing pyridinium ion acidities. It has been said that a ... single parameter treatment has the merit of simplicity but where this suggests correlations which are unrealistic in terms of chemical experience, then a dual parameter approach is necessary. 53 The correlation has the form of Eq. (8). While only one set of inductive-effect... 

Nonlinear resonances are important factors in reaction processes of systems with many degrees of freedom. The contributions of Konishi and of Honjo and Kaneko discuss this problem. Konishi analyzes, by elaborate numerical calculations, the so-called Arnold diffusion, a slow movement along a single resonance under the influence of other resonances. Here, he casts doubt on the usage of the term diffusion. In other words, Arnold diffusion is a dynamics completely different from random behavior in fully chaotic regions where most of the invariant structures are lost. Hence, understanding Arnold diffusion is essential when we go beyond the conventional statistical theory of reaction dynamics. The contribution of Honjo and Kaneko discusses dynamics on the network of nonlinear resonances (i.e., the Arnold web), and stresses the importance of resonance intersections since they play the role of the hub there. 

This is a surprising result, not so much with respect to the fact that the resonance effect coupling constants (which is expected from the factor fc fn), but concerning the amount of the contribution of oj (X = -0.51). 

Another factor influencing the electron distribution may be the contributions to the overall resonance hybrid of phenol made by structures 2—4. Notice that the effect of these structures is to withdraw electrons from the hydroxyl group and to make the oxygen positive ... 

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