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The van der Waals volume is a widely used descriptor in modeling physicochemical properties. However, the calculation of the van der Waals volume (V(vdW)) is rather time-consuming, from Bondi group contributions, for a large data set. A new method for calculating van der Waals volume has been developed, based on Bondi radii. The method, termed Atomic and Bond Contributions of van der Waals volume (VABC), is very simple and fast. The only information needed for calculating VABC is atomic contributions and the number of atoms, bonds, and rings. Then, the van der Waals volume (A(3)/molecule) can be calculated from the following formula: V(vdW) = summation operator all atom contributions - 5.92N(B) - 14.7R(A) - 3.8R(NR) (N(B) is the number of bonds, R(A) is the number of aromatic rings, and R(NA) is the number of nonaromatic rings). The number of bonds present (N(B)) can be simply calculated by N(B) = N - 1 + R(A) + R(NA) (where N is the total number of atoms). A simple Excel spread sheet has been made to calculate van der Waals volumes for a wide range of 677 organic compounds, including 237 drug compounds. The results show that the van der Waals volumes calculated from VABC are equivalent to the computer-calculated van der Waals volumes for organic compounds.

Partition coefficients, as values of log P, between water and two room-temperature ionic liquids and between water and an aqueous biphasic system have been correlated with Abraham's solute descriptors to yield linear free energy relationships that can be used to predict further values of log P, to ascertain the solute properties that lead to increased or decreased log P values, and to characterize the partition systems. It is shown that, in all three of the systems, an increase in solute hydrogen-bond basicity leads to a decrease in log P and an increase in solute volume leads to an increase in log P. For the two ionic liquid systems, an increase in solute hydrogenbond acidity similarly decreases log P, but for the aqueous biphasic system, solute hydrogenbond acidity has no effect on log P. These effects are rather smaller than those observed in traditional water-solvent systems. However, the ionic liquids appear to have an increased affinity for polyaromatic hydrocarbons as compared to traditional organic solvents. Principal component analysis and nonlinear mapping show that the three unconventional partition systems are considerably different from conventional water-organic solvent systems. IntroductionA major contemporary industrial challenge is to continued manufacturing beneficial chemical products while eliminating or substantially reducing the detrimental environmental consequences of the processes adopted. The Montreal Protocol 1 identified the need to reevaluate chemical processes to take account of their environmental impact, especially with regard to the use of volatile organic solvents. In addition, some 90% of hazardous waste is aqueous in nature, 2 and thus, industry is reliant upon efficient separations from liquid media. To this end, liquid-liquid separations are widely applied in the chemical process industry. Typically, because of their immiscibility with water, volatile organic solvents are often employed in such processes. 3 Taken together, these issues suggest that the elimination of the use of flammable toxic and volatile organic solvents in separations processing represents a significant step in the creation of a sustainable industrial technology. 4 A number of different approaches to this problem have been identified, including solvent-free synthesis, the use of water as a solvent, 5 the use of supercritical fluids, 6 and the use of ionic liquids. Recently, roomtemperature ionic liquids (RTILs) have received worldwide attention 7,8 as replacements for organic solvents in catalysis, 9 synthesis, 10,11 and separations processes. 12,13 Room-temperature ionic liquids, in contrast to conventional ionic liquids such as molten sodium chloride, which are only liquids at temperatures above 800°C, represent ionic salts that are liquid at room temperature. Many RTILs are liquids over a wide temperature range, and RTILs with melting points as low as -96°C are known. The constituents of many RTILs (being ionic) are constrained by high Coulombic forces and thus exert practically no vapor pressure abo...

Two sets of molecular descriptors, the five experimental Abraham, and the five COSMOments of Klamt's COSMO-RS, have been compared for a data set of 470 compounds. Both sets are considered as almost complete sets of LFER. The two sets of descriptors are shown to exhibit a large overlap as far as their chemical content. The chemical information however is distributed differently in each set with the Abraham set incorporating extra information in the excess molar refraction descriptor E. Regression equations have been constructed to predict the experimental Abraham descriptors from theoretically calculated COSMOments. The chemical interpretation of these equations is however difficult because of the lack of clustering which characterizes the distribution of chemical information through the two sets of descriptors. The predictability of the regression equations is tested successfully using a reasonably large set of data, and the method is compared to recent attempts to calculate the Abraham descriptors from various theoretical bases.