Marcia M. Meier

The Influence of β- and γ-Cyclodextrin Cavity Size on the Association Constant with Decanoate and Octanoate Anions

This work evaluates the influence of the β- and γ-cyclodextrin (CD) cavity size on the association constant (KCDA) with decanoate (C10) and octanoate (C8) anions. The spectral displacement technique with phenolphthalein was used to obtain the 1:1 association constant (KCDA) in NaHCO3/NaOH buffer pH 10.5 at 25 °C. The KCDA value obtained were 2.6 (±0.2) × 103, 2.5 (±0.5) × 102, for beta;CD–C10 and γCD–C10 inclusion complexes, and 5.1 (±0.2) × 102 and 4.7 (±0.2) × 101 for βCD–C8 and γCD–C8 inclusion complexes, respectively. The KCDA values of either acid with βCD is approximately 10 times higher than for the same acid with γCD, where as for the same cyclodextrin, the KCDA value is 5 times higher for the C10 association than for the C8. The data demonstrate that the cyclodextrin cavity size exerts a greater influence on the association constant than the chain length of the acid for these compounds. 1H NMR studies show that fatty acid protonation has a distinct effect on the chemical shift of CD protons.

SYNTHESIS, ELECTROCHEMICAL CHARACTERIZATION AND POTENTIOMETRIC TITRATION of trans-[RuCl2(L)4] COMPLEXES (L [dbnd] PYRIDINE DERIVED LIGANDS: 3-PYRIDINECARBOXYLIC ACID AND 4-PYRIDINECARBOXYLIC ACID)

Abstract In this work we report the synthesis, spectroscopic characterization, potentiometric titration and electrochemical studies performed on trans-[RuCl2(nic)4] (1) and trans-[RuCl2(i-nic)4] (II) complexes, where nic = 3-pyridinecarboxylic acid and i-nic = 4-pyridinecarboxylic acid. The complexes were synthesized using a ruthenium blue solution as a precursor in the synthetic route, and characterized by electronic spectroscopy, vibrational FT-IR spectroscopy, and 1H and 13C NMR. The results indicated a trans geometry. Cyclic voltammetry performed in water/ acetone (1:1) solution revealed a quasi-reversible process centered on the Ru(II) species and a dependence of the redox potential, E 1/2, on the pH. The electronic spectra showed that the MLCT bands were also affected by the pH, undergoing a hypsochromic shift (blue shift) as the pH increased. The spectroelectrochemical analysis indicated that the bands in the visible region progressively faded as new UV bands emerged during the oxidation process. T...

The influence of β‐cyclodextrin on goaty flavour ‐ Characterization of synthetic inclusion complexes with capric acid and caprylicacid

Sensory analysis shows that the addition of 0.4 per cent (w/v) of the macrocyclic β‐cyclodextrin (βCD) to goat’s milk improves the flavour and reduces its goaty taste, due to encapsulation of molecules responsible of this flavour. In vitro studies of the inclusion of formed complexes between βCD and short‐chain fatty acids, caprylic (C8...) and capric acid (C10...), were carried out by differential scanning calorimetry (DSC) and proton magnetic resonance (...1HNMR). Complex formation was confirmed by DSC, through the disappearance of the signs due to melting of C10 and C8 after the encapsulation process. The 1H NMR technique shows that C10... is included in the βCD cavity. The results suggest that βCD can encapsulate short‐chain fatty acids, making possible its use for masking of these compounds in goat’s milk and derivatives.