Hydrogen donor charged surface area

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. 

It is the relative positively charged surface area (RPCS) restricted to H-bond donor atoms, i.e. the positively charged surface area corresponding to the most positively charged atom that is also a possible hydrogen donor. 

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 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. 

In the above formula, D denotes that the summation goes over aU hydrogen donor surfaces, qo is the partial charge on H-bonding donor atoms, Sd is the solvent-accessible surface area of H-bonding donor atoms, and Stot is the total solvent-accessible molecular surface area. The electrostatic descriptors have intuitive interpretations. Their inclusion in QSAR models makes easy and clear analysis of the phenomenon under investigation. 

For each molecule in these struetures, 131 molecular descriptors were calculated. These included simple atom, bond and group eounts, hydrogen bond donor and acceptor counts, topological indices, a variety of partitioned and charge weighted surface areas and deseriptors of molecular size, shape, polarity... 

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

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