Hydrogen-bonding donor charged surface

The most important descriptor in this correlation was found to be the hydrogen-bonding donor charged surface area, which indicates that hydrogen bonding is a key factor for Hquid viscosity. 

Let SAd and SAa be the solvent accessible surface areas of hydrogen-bonding donors (d) and acceptors (a), respectively, and Qa the corresponding partial atomic charges, SASA the molecular solvent-accessible surface area the HB-CPSA descriptors are then defined as follows (note that the two different symbols encountered in the literature for some are considered as synonymous). 

The importance of electrostatics in the interaction of aromatics fluorine with cations and hydrogen bond donors can be visualized using electrostatic potential surfaces (Figure 20.37). In monofluorobenzene, the potential of the fluorine is concentrated on the unique fluorine present, whereas in polyfluorobenzene the negative charge is spread over several fluorine atoms. For this reason, monofluorobenzene may give stronger interactions. 

The descriptor uses readily calculable physicochemical properties from the topological structure. The descriptors used in this study were atomic weight, hydropho-bicity, molecular refractivity, atomic charge, polar surface area, hydrogen bond acceptors, and hydrogen bond donors. The authors note that Martin et al. [32] applied a similar approach for the design of diverse combinatorial libraries. 

Fully dehydroxylated covalent surfaces have a homopolar character, with no sensible charge separation. Adsorption on covalent solids is mainly physical covalent surfaces tend to be hydrophobic, and extensive hydroxylation requires high temperatures. Hydroxyl groups present on partially dehydroxylated surfaces show very weak acidic character. They act as hydrogen bond donors with most bases and can protonate only very strong bases. A typical example is silica [35]. 

Area-weighted surface charge of hydrogen bonding/donor donor atoms... 

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