Study of β‐Cyclodextrin Effect on Acidity Constant of 2‐(2H‐Benzo(d)(1,2,3) triazol‐2‐yl) phenol by Spectrophotometry

Abstract

The interaction of solutes withβ-cyclodextrin leads to apparent changes in their chemical properties, such as shifts in their absorption spectra and acid-base equilibrium. Formation of inclusion complexes between acid and/ or base forms of a compound withβ-CD can change the amount of conditional acidity constant. The acidity constants of 2-(2H-benzo (d)(1,2,3)triazol-2-yl)phenol (CFM) in water and in the presence of varying amounts ofβ-cyclodextrin at 25 °C and an ionic strength of 0.1 M have been determined spectrophotometrically. To evaluate the pH-absorbance date, a resolution method based on the combination of soft- and hard-modeling is applied. The acidity constant of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program was applied for determination of acidity constant. The pKavalue of CFis 8.50±0.10. The pKa value is decreased by increasingβ-CD concentration.

Encapsulation of Drug Molecules by Cucurbiturils: Effects on their Chemical Properties in Aqueous Solution

“…Cyclodextrins, with their preference for binding neutral and anionic guests, cause a decrease in the p K a value. As an example, the second p K a of 2‐(2′‐hydroxyphenyl)benzimidazole increases by 1.5 p K units upon complexation by CB[7],33d whereas binding to β‐cyclodextrin was reported to result in a decrease by about 0.6 p K units 60. Similar opposing effects on the p K a of guests bound to CB[ n ] and CD hosts have also been reported 45e.…”