Inclusion reactions of some phthalein and sulphophthalein compounds with cyclomalto-hexaose and -heptaose

OLIGOSACCHARIDE FUNCTIONALIZED NANOFIBROUS MEMBRANE

An attempt was made to incorporate β-Cyclodextrin (β-CD) onto the surface of the nanofiber to target potential applications in organic waste treatment. Phenylcarbomylated and azido phenylcarbomylated β-CD were successfully blended with poly(methyl methacrylate) (PMMA) and electrospun into nanofibrous membrane respectively with an approximate diameter of 900 nm. The presence of this selective agent on the surface of the nanofibers was confirmed by ATR-FTIR and XPS. To determine the functionalized membranes ability to capture small organic molecules, a solution containing phenolphthalein (PHP), a small organic molecule, was used. The results obtained showed that the functionalized nanofibrous membranes were able to effectively capture the PHP molecules. Thus the developed β-CD functionalized nanofibrous membranes may have the potential to capture similar small organic molecules in organic waste.

The influence of beta-cyclodextrin on acid-base and tautomeric equilibrium of fluorescein dyes in aqueous solution

The protolytic equilibrium of fluorescein in aqueous solutions was studied in the presence of cycloheptaamylose (beta-cyclodextrin, or beta-CD). The constants of stepwise ionization of the dye (H(3)R(+)left arrow over right arrowH(2)Rleft arrow over right arrow HR(-)left arrow over right arrowR(2-)), K(a0), K(a1), and K(a2) were determined using vis-spectroscopy at ionic strength 0.05 M (NaCl+buffer) and 25 degrees C. In the presence of 0.0086 M beta-CD, the indices of ionization constants are as follows: pK(a0)=1.21+/-0.12, pK(a1)=5.08+/-0.03, pK(a2)=6.35+/-0.02. The changes in these pK(a)s, as compared with the values determined without cyclodextrin, are unequal. Namely, the pK(a0) value decreases by 1.0, while the pK(a1) value increases by 0.7. Thus, the introduction of beta-CD allows to govern the ratios K(a0)/K(a1) and K(a1)/K(a2), which are equal to, respectively, 141 and 151 in water, and 7.4 x 10(3) and 18.6 with cyclodextrin added. Rationalization of the observed phenomenon is possible taking into account the detailed scheme of protolytic equilibrium. Conclusions concerning tautomerism of dye molecules were deduced from absorption spectra; the fractions of tautomers, tautomerization constants, and microscopic ionization constants were evaluated. These data allow concluding that the main reason for the aforementioned pK(a) alterations is the binding of H(2)R by the cyclodextrin cavity accompanied by turning these neutral species into the colorless lactone. The host-guest interaction of neutral species of fluorescein isothiocyanate, 2,7-dichlorofluorescein, and 3',4',5',6'-tetrachlorofluorescein also results in the cyclodextrin-assisted shift of tautomeric equilibrium. Such nature of interactions is proved by the addition of competing agents, camphor-4-carboxylic acid and sodium n-nonylsulfonate, which results in the removing of neutral dye species from the cycloheptaamylose cavity.

Enhanced protonation of cresol red in acidic aqueous solutions caused by freezing

The protonation degree of cresol red (CR) in frozen aqueous solutions at 253 or 77 K, containing various acids (HF, HCl, HNO3, H2SO4, and p-toluenesulfonic acid), sodium hydroxide, NaCl, or NH4Cl, was examined using UV/Vis absorption spectroscopy. CR, a weak organic diacid, has been selected as a model system to study the acid-base interactions at the grain boundaries of ice. The multivariate curve resolution alternating least-squares method was used to determine the number and abundances of chemical species responsible for the overlaying absorption visible spectra measured. The results showed that the extent of CR protonation, enhanced in the solid state by 2-4 orders of magnitude in contrast to the liquid solution, is principally connected to an increase in the local concentration of acids. It was found that this enhancement was not very sensitive to either the freezing rate or the type of acid used and that CR apparently established an acid-base equilibrium prior to solidification. In addition, the presence of inorganic salts, such as NaCl or NH4Cl, is reported to cause a more efficient deprotonation of CR in the former case and an enhanced protonation in the latter case, being well explained by the theory of Bronshteyn and Chernov. CR thus served as an acid-base indicator at the grain boundaries of ice samples. Structural changes in the CR molecule induced by lowering the temperature and a presence of the constraining ice environment were studied by the absorption and 1H NMR spectroscopies. Cryospheric and atmospheric implications concerning the influence of acids and bases on composition and reactivity of ice or snow contaminants were examined.