POPULATION CHARACTERISTICS OF CYCLODEXTRIN COMPLEX STABILITIES IN AQUEOUS-SOLUTION

Binding constants (K-11) of 1:1 complexes of alpha-cyclodextrin, beta- cyclodextrin, and gamma-cyclodextrin with many substrates (guests) wer e collected from published sources and subjected to statistical analys is. All systems refer to 25 +/- 5 degrees C and aqueous solution. The frequency distributions of log K-11 are satisfactorily described by no rmal distributions with the following parameters (n = number of comple xes, mu = population mean, sigma = population standard deviation): alp ha-cyclodextrin, n = 663, mu = 2.11, sigma = 0.90; beta-cyclodextrin, n = 721, mu = 2.69, sigma = 0.89; gamma-cyclodextrin, n = 166, mu = 2. 55, sigma = 0.93. Stabilities of pairs of cyclodextrin complexes with a common substrate are not precisely correlated, but they do not appea r to be wholly independent quantities. The stabilities of alpha-cyclod extrin complexes are consistent with a recent interpretation of solven t effects on alpha-cyclodextrin complex stabilities.