Hydration systems recent advances

A most significant advance in the alkyne hydration area during the past decade has been the development of Ru(n) catalyst systems that have enabled the anti-Markovnikov hydration of terminal alkynes (entries 6 and 7). These reactions involve the addition of water to the a-carbon of a ruthenium vinylidene complex, followed by reductive elimination of the resulting hydridoruthenium acyl intermediate (path C).392-395 While the use of GpRuGl(dppm) in aqueous dioxane (entry 6)393-396 and an indenylruthenium catalyst in an aqueous medium including surfactants has proved to be effective (entry 7),397 an Ru(n)/P,N-ligand system (entry 8) has recently been reported that displays enzyme-like rate acceleration (>2.4 x 1011) (dppm = bis(diphenylphosphino)methane).398... 

It is important to propose molecular and theoretical models to describe the forces, energy, structure and dynamics of water near mineral surfaces. Our understanding of experimental results concerning hydration forces, the hydrophobic effect, swelling, reaction kinetics and adsorption mechanisms in aqueous colloidal systems is rapidly advancing as a result of recent Monte Carlo (MC) and molecular dynamics (MO) models for water properties near model surfaces. This paper reviews the basic MC and MD simulation techniques, compares and contrasts the merits and limitations of various models for water-water interactions and surface-water interactions, and proposes an interaction potential model which would be useful in simulating water near hydrophilic surfaces. In addition, results from selected MC and MD simulations of water near hydrophobic surfaces are discussed in relation to experimental results, to theories of the double layer, and to structural forces in interfacial systems. 

Perhaps the least-understood set of interactions involving membranes is that between bilayers or other amphiphilic surfaces. Yet, no discussion of membrane functions would be complete without considering these forces because of their essential role in cell-cell interactions and membrane fusion. The forces acting between membranes are often called hydration forces . This name originates in the tendency at one time to ascribe many unexplained or ubiquitous effects seen in various colloidal systems to the effects of aqueous solvation. However, it is still unclear, despite recent experimental and theoretical advances, whether or not these forces are mainly due to hydration , as understood in the conventional sense. In this section, we describe some of the major issues involving hydration forces between membranes, and provide a summary of selected theoretical and experimental works. More complete reviews, with different emphases, can be found in articles by Israelachvili, et al. [136,137] and Leikin, et al. [138]. 

---