A Comparison between the Two General Sets of Linear Free Energy Descriptors of Abraham and Klamt

Abstract

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.

A Revisited Definition of the Three Solute Descriptors Related to the Van der Waals Forces in Solutions

“…The 100% GLC determination of solutes parameters not seemingly being anymore developed, an alternative way has been followed consisting in the pooling of those presently available with those published by Abraham and co-authors [12] [13]. In this step the Abraham data have been suitable transformed as mentioned above, and those in gas or solid state at room temperature have been excluded.…”

Descriptors for ions and ion-pairs for use in linear free energy relationships

“…Bittermann et al [7] used COSMOmic to determine partition coefficients of ionic species, and Ingram et al [11] used COSMO-RS to calculate partition coefficients of ion-pairs. The most relevant work is that of Cho et al [68] who first calculated the Klamt descriptors and then used the equations of Zissimos et al [69] to convert them to the Abraham parameters E, S, A, B and V for ions and ionic liquids. This would appear to be a way forward to deal with the problem of lack of ionic descriptors, and could open up the application of Eq.…”

“…Log of ionic liquids (ILs) using the COSMO-RS method, and then converted these to Abraham descriptors through the equations given by Zissimos et al [69]. They then used a variation of Eq.…”

Enthalpy of solvation correlations for organic solutes and gases dissolved in 1-propanol and tetrahydrofuran

“…If one is unable to locate sufficient experimental data for performing the fore-mentioned regression analysis, commercial software [173] is available for estimating the molecular solute descriptors from the structure of the compound. Several correlations [174,175] Abraham as the source of Eqn. 8.…”