Complexation of benzoic, 4-methylbenzoic and R- and S-2-phenylpropanoic acids and their conjugate bases by 3A-amino-3A-deoxy-(2AS,3AS)-b-cyclodextrin in aqueous solution
Date
1995
Authors
Dhillon, R.
Easton, C.
Lincoln, S.
Papageorgiou, J.
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Advisors
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Volume Title
Type:
Journal article
Citation
Australian Journal of Chemistry, 1995; 48(6):1117-1124
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Abstract
<jats:p>A potentiometric titration study of the complexation of benzoic, 4-methylbenzoic, and (R)- and (S)-2-phenylpropanoic acids and their conjugate bases by 3A-amino-3A-deoxy-(2AS,3AS)-ß- cyclodextrin, ßCD3NH2, in which the amino group may be protonated to produce a singly charged species, ßCD3NH3+, is reported. In aqueous solution at 298.2K and I = 0.10 mol dm-3 ( KCl ), the complexation constants for the complexes indicated have the values (in dm3 mol-1) shown in parentheses: benzoic acid.ßCD3NH3+ (KHA = 110±10); benzoate.ßCD3NH3+ (KA = 19±2); 4-methylbenzoic acid.ßCD3NH3+ (KHA = 210±10); 4-methylbenzoate.ßCD3NH3+ (KA = 21±3); (R)- and (S)-2-phenylpropanoic acid.ßCD3NH3+ (KRHA = 64±8, KSHA = 57±5); (R)- and (S)-2-phenylpropanoate.ßCD3NH3+ (KRA = 51±6, KSA = 32±6); and (R)- and (S)-2-phenylpropanoate.ßCD3NH2 (KRA' = 13±7; KSA' is too small to quantify reliably). These complexation constants are substantially less than those for the host-guest complexes formed by the isomeric 6A-amino-6A-deoxy-ß-cyclodextrin and also for those formed by ß-cyclodextrin. The origins of these differences are discussed.</jats:p>