Ionic transformations, spontaneous

Scheme 8.7) and the Favorskii rearrangement (Scheme 8.8). These examples were presented within the context of alkyl shifts and the related hydride shifts. Through these examples, the concepts of ionic stability and spontaneous ionic transformations to... 

For atoms with several equivalent electrons excited states which are energetically equivalent to ionic states are possible. As a result there is a certain probability that they transform spontaneously into ions by emission of an electron. This transition can be investigated wave-mechanically and in this way a lifetime for the first state and a theoretical value for the probability We mentioned above can be obtained. If we compare this to the probability Wq of a transition to a nonexcited state of the atom by emission of a light quantum then the ratio of these two probabilities can be roughly tested with the help of the Auger experiment on the fluorescence yield of absorbed X-rays. Finally the influence of the spontaneous transformation on the dispersion is investigated. 

This program is applied to the 90 reactions for which Af H° are known for all species. The reactions have all been written in the direction in which they are spontaneous at 298.15 K, pH 7, and 0.25 M ionic strength. The standard transformed Gibbs energies of formation and standard transformed enthalpies of formation are in kJ moP and the standard transformed entropies of formation are in J K" moP . 

The description of structure in complex chemical systems necessarily involves a hierarchical approach we first analyse microstructure (at the atomic level), then mesostructure (the molecular level) and so on. This approach is essential in many biological systems, since self-assembly in the formation of biological structures often takes place at many levels. This phenomenon is particularly pronounced in the complex structures formed by amphiphilic proteins that spontaneously associate in water. For example myosin molecules associate into thick threads in an aqueous solution. Actin can be transformed in a similar way from a monomeric molecular solution into helical double strands by adjusting the pH and ionic strength of the aqueous medium. The superstructure in muscle represents a higher level of organisation of such threads into an arrangement of infinite two-dimensional periodicity. 

We discuss now how the morphology of a hydrophobic polymer can be modified by the contact with water. For the reasons described in previous section, this transformation depends on the amount of gases dissolved and the ionic species present. The typical size and nature of formed pattern can then be tuned if these variables are precisely controlled. Two processes must be considered. First, the GNs have a transforming effect, as described in next chapter. Second, the specific adsorption of ions may induce spontaneous surface deformation. 

---