Solvent-solute clustering occurrence

Finally, the PFR of 1-naphthyl acetate has been used to demonstrate the occurrence of solvent-solute clustering in supercritical carbon dioxide. This is... 

Inorganic mesoporous materials such as zeolites have also served as hosts for aromatic esters whose irradiation leads to changes in the selectivity of the photoproducts ortho preference) in comparison with the rearrangement in homogeneous media., - Finally, the photochemical Fries rearrangement of naphthyl acetate has shown the occurrence of solvent-solute clustering in supercritical carbon dioxide. " ... 

The ionic clusters observed are not limited to aqueous electrolyte solutions only. In fact very similar results were obtained for methanolic solutions as well [25]. This shows that sufficiently large and stable ionic clusters are a fairly common occurrence whenever ions are dissolved in polar solvents. The clusters are an essential factor in the facilitation of reverse osmosis purification. Since many industrially important solutions include ions in polar solvents, it is important to account for them in separation involving such solvents. 

Most investigations of photoinduced electron transfer have been performed in condensed phases. Much less is known about conditions that permit the occurrence of intramolecular ET in isolated (collision-free) molecular D-A systems. A powerful method for this kind of study is the supersonic jet expansion teehnique (which was originally developed by Kantrowitz and Grey in 1951 [66]) combined with laser-induced fluorescence (LIF) spectroscopy and time-of-flight mass spectrometry (TOF-MS). On the other hand, the molecular aspects of solvation can be studied by investigations of isolated gas-phase solute-solvent clusters which are formed in a supersonic jet expansion [67] (jet cooling under controlled expansion conditions [68] permits a stepwise growth of size-selected solvation clusters [69-71]). The formation of van der Waals complexes between polyatomic molecules in a supersonic jet pro-... 

In addition to showing that solvent-free melt and sublimation crystallization conditions offer an attractive route to new polymorphs, a CSD survey of these methods of crystallization and the frequency of Z was performed (Table 3-5). There is a dramatic increase in the occurrence of Z > 3 crystal structures when melt or sublimation crystallization conditions are used [20]. The occurrence of high Z in melt crystallization and sublimation methods is ascribed to the rapid cooling of the hot liquid or vapor (100-300° C) in the open flask or on the cold finger (kinetic phase), conditions under which hydrogen-bonded clusters are likely to condense in a pseudo-symmetric crystalline arrangement. On the other hand, the slower nucleation process of solution crystallization gives the frequent situation of Z < 1 (88% hits). 

In contrast, the AFM pictures as well as cryo-TEM of sample CB-PLL55 prepared from 5 mM NaBr aqueous solution (Fig. 20) show extended cylinders. The cylinders exhibit undulations of the cross-section that are reminiscent of the pinned clusters [74, 91] postulated by scaling arguments. The occurrence of pearl-necklace-type structures, where pinned clusters of side chains alternate with regimes that are almost free of side chains, has also been seen in simulations of bottlebrushes, provided one has poor solvent conditions. These clusters are formed by collective collapse of several neighboring side chains [92]. We return to this problem in Sect. 3.5. 

---