Cyclodextrin complexes of substituted perbenzoic and benzoic acids and their conjugate bases: free energy relationships show the interaction of polar and steric factors

The stability constants of the complexes of α-cyclodextrin and 4-methyl-, 4-nitro-, 4-sulfonato- and 3-chloro-substituted perbenzoic acids, perbenzoates and benzoates, but not benzoic acids, show linear free energy relationships. In contrast to α-cyclodextrin, the stability constants of the β-cyclodextrin complexes of perbenzoic acid and benzoic acids do show the same trend. The stability constants are discussed in terms of the orientation of the guest species in the cyclodextrin cavity.