New possibilities for estimating octanol/water partition coefficients (logP) and the water solubility (S w ) were investigated using Kovàts retention indices (I) obtained from GLC retention data for 132 volatile organic compounds belonging to 7 different chemical classes (hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters and halogen compounds). Application of the multilinear regression method led to six equations, all involving index I, as follows: (i) direct correlation logP vs. I (eq.1); (ii) logP vs. I , molar refractivity, and surface tension (eq. 2); (iii) logP vs. I and structural characteristics (eqs. 3, 4 and 6); (iv) logP vs. the I/S w ratio (eq. 5). Excepting eq. 1 (which showed relatively weak correlations), eqs. 2 -6 can provide reliable values for logP and for logS w as proved by the significant statistical parameters. The general models presented through eqs. 2 -6 may also be applied in estimation of other biological and/or ecological important properties, which are linearly dependent on the logP or log S w values. By generalization, a new calculation method is suggested (eq. 7), in order to allow the estimation of logP or logS w in terms of the number of bonds and the Kovàts retention index.

No abstract

Abraham's equation was employed in order to investigate nonspecific intermolecular interactions involving liquid crystals. Several aromatic azo derivatives, proved to have liquid crystal behavior, were used as stationary phases in capillary gas chromatography. The polarizability, polarity, hydrophobicity and hydrogen-bond donor or acceptor characters were estimated using the Abraham solvation model. Calculations were based on the isothermal retention times for 25 compounds, in the temperature range between 70˚ and 170˚C, both in the heating and the cooling mode. The descriptors R, , , , and logL 16 (Abraham parameters) were converted into orthogonal descriptors following Randi 's procedure. The above-mentioned properties involve the r, s, a, b and l coefficients, respectively, which were determined by means of multilinear regression applied to the considered set. Following the orthogonalization procedure, the polarizability term (rR*) was found to be statistically insignificant in the case of the studied compounds. Plots of these coefficients vs temperature are discussed, in order to allow estimations regarding the retention mechanism and contributions of polar and Van der Waals interactions. The variation of properties (e.g. polarity, hydrogen-bond donor and hydrogen-bond acceptor character) with temperature was assigned to the changes in the molecular geometry of the compound used as stationary phase.

Various primary and secondary alcohols (I) and (III) are oxidized to the corresponding aldehydes (II) and ketones (IV), resp., using silica supported TEMPO as a heterogeneous catalyst and nitrosonium tetrafluoroborate as a co‐catalyst.