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On simple experimental evidence confirmed by HPLC data of supramolecular aggregation and aggregate mobility with S(+)-naproxen in aqueous ethanol solution

Sajewicz M., Gontarska M., Kowalska T.

Acta Chromatographica

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2012

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Vol. 24, no. 1

131--141

EN

In our earlier studies performed with the use of thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), polarimetry, and several other instrumental techniques, we have provided abundant experimental evidence for the oscillatory chiral conversion and the oscillatory condensation of the low-molecular-weight carboxylic acids from the groups of profen drugs, amino acids, and hydroxy acids. We have also proposed several kinetic-diffusive models aimed at elucidation of these striking phenomena, which in the diffusive term assumed contribution from the density inhomogeneity of the investigated liquid systems. Moreover, each model laid special emphasis on the importance of cyclic H-bonded carboxylic acid homodimers of the SS and RR type. In this paper, we introduce a simple experimental approach enabling convenient registration of the density inhomogeneity in the S(+)-naproxen solution prepared in 70% aqueous ethanol. To this effect, we use a zooming scanner that is able to scan this solution in a Petri dish placed in UV light (λ = 254 nm). Scanning in the selected time intervals allows tracing the dynamics of supramolecular aggregation of the investigated profen drugs. The mobility of these aggregates can probably result from the energy released in the process of chemical polycondensation. The obtained results seem to correlate well with those originating from HPLC, and the relevant conclusions are drawn. It seems possible that the zooming scanner can prove helpful in monitoring some other interesting chemical processes as well, thus contributing to the studies on the mechanism and kinetics of the nonlinear organic reactions.

2

Effect of ionic strength of the solution of some hydrogen — bonded interpolymer complexes on the stability and thermodynamic parameters

Ahmadi M. H., Rajabi F. H., Gholehzadeh A.

Polimery

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2009

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T. 54, nr 4

261-265

EN

The effect of ionic strength of the solution on the complex formation of poly(acrylic acid) (PAA) with poly(vinyl pyrrolidone) (PVP) has been studied in aqueous solutions containing various inorganic salts (NaCl, KCl, NH4Cl). Stability constant (Ks), degree of linkage (...) and related thermodynamic parameters (..., ... and ...) have been compared for different complexation systems. The comparative study indicated considerable difference in the values of these parameters, which has been explained on the basis of relative strength of H-bond present in different systems.

PL

Scharakteryzowano wpływ siły jonowej roztworu na proces komleksowania w układzie poli(kwas akrylowy)/poli(winylopirolidon); badania prowadzono w roztworach wodnych zawierających różne sole nieorganiczne (NaCl, KCl, NH4Cl). Określano stałą stabilności (Ks, rys. 1), stopień związania (?, tabela 2) oraz podstawowe parametry termodynamiczne (?G0, ?H0 and ?S0, rys. 2 i 3, tabela 3) omawianych układów ulegających skompleksowaniu. Wyniki wskazują na istotne różnice wartości wspomnianych parametrów w zależności od względnej siły wiązań wodorowych występujących w rozpatrywanych roztworach a także od oddziaływań hydrofobowych. Doświadczalną podstawę badań stanowiły pomiary pH (tabela 1).

3

The crystal and molecular structure of cyclic thioamide beta-dikotone derivatives. Intramolecular H-bonding and the problem of quasiaromaticity

Anulewicz R., Krygowski T.M., Jagodziński T.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 2

439-448

EN

Crystal and molecular structures of the 2,6-dioxocyclohexanethiocarboxanilide (I), 4,4-dimethyl-2,6-dioxocyclohexanethiocarboxanilide (II) and 1,3-indandione-2- thiocarboxanilide (III) have been determined by use of X-ray diffraction technique on a Kuma-diffractometer. Crystal data for compound (I): C13H13N1O2S1, M-r=247.32, monoclinic, C2/c, a=22.704(5)A, b=7.312(1)A, c=17.192(3)A, beta=123.07(3), Z=8, R=0.0597 for 2181 reflections. Compound (II): C15H17N1O2S1, M-r=275.36, triclinic, P-1, a=10.748(1)A, b=9.223(2)A, c=7.346(2)A, alpha=91.21(3), beta=100.36(3), gamma=76.01(3), Z=2, R=0.0733 for 2485 reflections. Compound (III): C16H11N1O2S1, M-r=281.12, triclinic, P-1, a=6.945(3)A, B=8.786(1)A, c=12.435(3)A, alpha=86.97(3), beta=73.78(3), gamma=66.74(3), Z=2,R=0,0696 for 2361 reflections. Of the two potentially H-bonding systems of each of the title compounds one that with OH...S, is stronger and this resilts in a stronger pi-electron delocalization. This is quantitatively measured by HOMA index, which is by ca. 0.3 units larger than for the other H-bonding system, the one with the NH...O bridge.