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Solute-solvent Interactions (solute-solvent + interaction)
Selected AbstractsAnalysis of water solubility data on the basis of HYBOT descriptorsMOLECULAR INFORMATICS, Issue 9-10 2003Part 2. Abstract Solubility data of 787 organic liquids (electrolytes and non-electrolytes) with diverse structures has been quantitatively described by physicochemical property descriptors. Special effects like intra - and intermolecular hydrogen bonds have been shown to be very important for water solubility. It is found that an important part of the solute-solvent interaction is neglected in all correlations of logS with (only) logP, as in this case the solute H-bond donor effect is not considered. As expected intramolecular hydrogen bonds lead to reduced solubility, whereas intermolecular hydrogen bonds (both HB donors and acceptors) of solutes result in higher solubility. An exception to the latter rule are carboxylic acids which due to intermolecular HB-induced dimerization in the pure liquid phase of acids show a three times lower solubility as expected on the basis of their molecular properties. A volume-related term (molecular polarizability ,) was found to have an essential negative contribution to solubility. For the first time the solubility increasing effect of partial ionization of weak acids and bases in saturated aqueous solutions has been quantitatively considered for sets of compounds by exact calculation of the pH determined by the solutes aqueous solubility and pKa value(s). [source] Polar aspects of intramolecular interactions in 2-amino-5-nitro-4-methylpyridines and 2-amino-3-nitro-4-methylpyridinesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2000M. Wandas The dipole moments of twelve 2- N -substituted amino-5-nitro-4-methylpyridines (I-XII) and three 2- N -substituted amino-3-nitro-4-methylpyridines (XIII-XV) were determined in benzene. The polar aspects of intramolecular charge-transfer and intramolecular hydrogen bonding were discussed. The interaction dipole moments, ,int, were calculated for 2- N -alkyl(or aryl)amino-5-nitro-4-methylpyridines. Increased alkylation of amino nitrogen brought about an intensified push-pull interaction between the amino and nitro groups. The solvent effects on the dipole moments of 2- N -methylamino-5-nitro-4-methyl-(I), 2- N,N -dimethylamino-5-nitro-4-methyl- (II) and 2- N -methylamino-3-nitro-4-methylpyridines (XIII) were different. Specific hydrogen bond solute-solvent interactions increased the charge-transfer effect in I, but it did not disrupt the intramolecular hydrogen bond in XIII. [source] Estimation of Carboxylic Acid Ester Hydrolysis Rate ConstantsMOLECULAR INFORMATICS, Issue 9-10 2003H. Hilal Abstract SPARC chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid esters from molecular structure. The energy differences between the initial state and the transition state for a molecule of interest are factored into internal and external mechanistic perturbation components. The internal perturbations quantify the interactions of the appended perturber (P) with the reaction center (C). These internal perturbations are factored into SPARC's mechanistic components of electrostatic and resonance effects. External perturbations quantify the solute-solvent interactions and are factored into H-bonding, field stabilization and steric effects. These models have been tested using 1471 measured hydrolysis rate constants in water and mixed-solvent systems at different temperatures. The aggregate RMS deviation of the calculated versus observed values was 0.374,M,1s,1; close to the intralaboratory experimental error. [source] Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis(thiocyanato)(2,2,-bipyridyl)platinum(II)CHINESE JOURNAL OF CHEMISTRY, Issue 9 2007Xiao-Ying Hu Abstract This paper presents a Density Functional or Time Dependent Density Functional (DFT/TDDFT) study of the molecular and electronic structures, optical absorption and emission spectra of three linkage isomers:bis(isothiocyanato-S)(2,2,-bipyridyl) platinum(II) ([Pt(SCN)2(bpy)]), (isothiocyanato-S)(thiocyanato-N)-(2,2,-bipy- ridyl) platinum(II) ([Pt(SCN)(NCS)(bpy)]), and bis(thiocyanato-N)(2,2,)-bipyridyl)platinum(II) ([Pt(NCS)2(bpy)]), in which different coordination ligands based on the N- and S-coordination of the thiocyanato ligands control the luminescent color. The electronic structures were studied using the B3LYP functional. Optimized geometries were compared to the experimentally observed structures. TDDFT calculation was carried out to investigate the excited singlet and triplet states. Calculations have been performed both in vacuo and in solvents, using a polarized continuum model (PCM) to account for solute-solvent interactions. Inclusion of the solvent led to a significant energy change, and as a consequence, the computed spectrum calculated in the presence of the solvent was in good agreement with the experimental determinations. The first two absorptions were found to originate from mixed platinum-SCN (or NSC) to bipyridyl-,* transitions rather than pure metal-to-ligand-charge-transfer (MLCT) transitions, whereas the higher-energy bands arose from intraligand ,,,* transitions. The stretching frequencies of C,N have been calculated both in the ground and excited states, which are relative to the charge transition during the excitation. In addition, different sizes of basis sets were also discussed in this paper. [source] | ||||||||||