Adrian Beteringhe

QSAR study using topological indices for inhibition of carbonic anhydrase II by sulfanilamides and Schiff bases

A QSAR study of two sets of carbonic anhydrase inhibitors is presented using a variety of molecular descriptors including topological indices. The first set consists of 29 benzenesulphonamides, and the second set includes 35 sulphanilamide Schiff bases. Two regression methodologies have been used involving ridge regression and the CODESSA program, and their results are compared with those of previous QSAR studies. Good correlations were found for the former set, and less satisfactory results for the latter set when the number of molecular descriptors is kept below five.

QSPR study on pKa values of N-methoxy-polynitroaniline derivatives

A QSPR study is presented for acidities of thirteen N-methoxy-polynitroaniline derivatives. Hammett σ values are known for meta and para substituents, and in the present study values are introduced for ortho-substituents in these N-methoxy-polynitroaniline derivatives. Hammett σ values for ortho-substituents in these N-methoxy-polynitroaniline derivatives were obtained by multiplying para values with 0.65.

Structural factors influencing the reaction rates of 4-aryloxy-7-nitrobenzofurazans with amino acids

An interesting observation was made when studying the SNAr reaction between several 4-aryloxy-7-nitrobenzofurazans (2) and several amino acids leading to the apparition of detectable fluorescence from the substitution products3. Acidic amino acids reacted very slowly=while basic amino acids react fastest with2 having an unsubstituted phenyl or a 4-formyl-phenyl Ar group. Amongst neutral amino acids, proline reacts fastest at room temperature after 100 min. With2 having a methoxy-subtituted Ar group.

O-Methyloximes of Testosterone and of 17α-Methyltestosterone: TLC and QSPR Study of R F Values

The Z (1b and 2b, respectively) and E diastereomers (1c and 2c, respectively) of the O-methyloximes of testosterone (1a) and 17a-methyltestosterone (2a) have been synthesized and separated by TLC. 1H NMR assignments confirmed the corresponding structures. The TLC RF values of these six compounds could be rationalized by a quantitative structure-property relationship (QSPR) using one topological/topographical index.

Study of Intermolecular Interactions Involved in Capillary GLC with Liquid Crystal Compounds as Stationary Phases

Abrahams 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.

Algebraic conditions, in terms of the solvent partition constants, for the separation of chemical classes by gas–liquid chromatography

ABSTRACT The interdependence between the solvation Gibbs energy of several functional groups and the solvent partition coefficients was studied, starting from gas chromatographic data. Single-parameter relationships were derived for the –OH, -CHO, -CO, -O-,-COO (acetate), -COO (methyl ester)-, and -CN group increments. The obtained equations were found to be temperature independent, and could be successfully used for the evaluation of 19 stationary phases with respect to certain separation questions. The selectivity problem was converted into an inequality system. The graphical solution of such a system provides an image of the separation abilities of a sorbent material with respect to a given pair of solutes, and allows an efficient comparison of a great number of stationary phases. The graphs are also illustrative for the temperature effect on the selectivity features.

New N-aryloxy-phthalimide derivatives. Synthesis, physico-chemical properties, and QSPR studies

AbstractStarting from N-hydroxyphthalimide 1 and the reactive fluoro- or chloro-nitroaryl derivatives 2, 3 and 4a-e (2-chloro-3,5-dinitropyridine; 3, NBD-chloride; 4a, 1-fluoro-2,4-dinitrobenzene; 4b, picryl chloride; 4c, 4-chloro-3,5-dinitrobenzotrifluoride; 4d, 2-chloro-3,5- dinitrobenzotrifluoride; 4e, 4-chloro-3,5-dinitrobenzoic acid) the corresponding N-(2-nitroaryloxy)-phthalimide derivatives 5a-e, or 6 and 7 were obtained and characterized by IR, UV-Vis 1H-NMR and 13C-NMR spectroscopy. The TLC behavior and the hydrophobicity of these derivatives have been experimentally evaluated by RM0 parameters (using RP-TLC). The experimental RM0 parameters were compared with the calculated partition coefficient, log P. A QSPR study was also performed to establish possible correlations between the structure and physical properties (λmax and RM0) of compounds 5a-e, 6, and 7.