1959 (1982).Competitive inclusion in P-cyclodextrin between 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy and chloro-substituted acetic acids has been monitored by esr spectroscopy. The temperature dependence of the rotational correlation frequencies calculated by Kivelson's equation, using esr spectra of the radical, suggests that a structural change of P-cyclodextrin occurs at about 30°C and that trichloroacetic acid is included extensively at 20-3S°C, but significant inclusion of acetic acid is not observed. The degree of competitive inclusion is in the order of trichloro, dichloro, and rnonochloroacetic acids over the range of 20-80°C. Carbon-13 nmr studies also prove the inclusion of trichloroacetic acid showing an inclusion shift of the trichloromethyl carbon by 1.4 ppm.

The rate of the decarboxylation of trichloroacetic acid (abbreviated as TCAH) in the presence of β-cyclodextrin(βCD) in an aqueous solution of sodium hydroxide has been followed by the determination of the remaining TCAH. The rate equation was given by Rate=(k_1T+k_1TCC_βCD)C_TCAH^1/2+(k_2T-k_2TCC_βCD)C_TCAH. A probable bimolecular decarboxylation mechanism which involves the unionized molecule of TCAH rather than the anion was proposed and discussed.