trans- Cinnamic Acid–α-Cyclodextrin System as Studied by Solubility, Spectral, and Potentiometric Techniques

Stoichiometric model of α-cyclodextrin complex formation

“…Interpretation of the initial rising portion in terms of 1:l plus 1:2 complexes, as described previously (1,6), shows that the slope of the line is 0.50, which implies that K11 = l/so, where s g is the solubility at Lt = 0. This relationship gives K~I = 105 M-I; with K I I = l/so, the data can he fitted regardless of the value of K l z .…”

“…A previous study (1) showed that trans-cinnamic acid forms 1:l (SL) and 1:2 (SL2) complexes' with cu-cyclodextrin (cyclohexaamylose) in aqueous solution. Therefore, knowledge of the factors that influence the stoichiometric relationships in such a system and that control the magnit.udes of the complex stability constants was desired.…”

“…The complexing behavior was studied by the solubility, spectral, and kinetic techniques. Procedures-The solubility and spectral studies were carried out as descrihed for cinnamic acid (1). except that in the solubility technique the supernatant solution was analyzed spectrophotometrically after appropriate dilution.…”

Potentiometric Study of Molecular Complexes of Weak Acids and Bases Applied to Complexes of α-Cyclodextrin with para -Substituted Benzoic Acids

“…If "a+]/& = V2, then the pH can be interpreted as pKa' (apparent dissociation constant), and Eq. 24 becomes ApKa' = log C, or:which is the equation used previously(5) to interpret the cinnamic acid-a-cyclodextrin system. This derivation shows the level of approximation involved in interpreting ApH as ApKa'.…”

The role of water release from the cyclodextrin cavity in the complexation of benzoyl chlorides by dimethyl-β-cyclodextrin

“…[6][7][8][9][10] Most CD-G complexes have a 1:1 and 2:1 stoichiometry but complexes of 1:2 and 2:2 stoichiometries have also occasionally been reported. [11][12][13][14][15][16][17][18][19][20][21] The driving forces leading to the inclusion complexation of cyclodextrin were thought to include electrostatic, van der Waals, hydrophobic, charge-transfer and hydrogen-bonding interactions. 22 Additional factors are penetration of the hydrophobic part of the G molecule into the CD cavity and dehydration of the organic G, 7,23,24 conformational changes, 3,6,[25][26][27] , and the release of water molecules from the CD.…”