Noncovalent Catalysis by the Cycloamyloses

In contrast to the reactions of the cycloamyloses with esters of carboxylic acids and organophosphorus compounds, the rate of an organic reaction may, in some cases, be modified simply by inclusion of the reactant within the cycloamylose cavity. Noncovalent catalysis may be attributed to either (1) a microsolvent effect derived from the relatively apolar properties of the microscopic cycloamylose cavity or (2) a conformational effect derived from the geometrical requirements of the inclusion process. Kinetically, noncovalent catalysis may be characterized in the same way as covalent catalysis that is, /c2 once again represents the rate of all productive processes that occur within the inclusion complex, and Kd represents the equilibrium constant for dissociation of the complex. 

The manifestation of noncovalent catalysis as a microsolvent effect is illustrated by cycloamylose-catalyzed decarboxylations of activated carboxylic acid anions. Anionic decarboxylations, as illustrated in scheme VII, are generally assumed to proceed by a rate-determining heterolytic 

Kinetic Parameters for the Cycloheptaamylose-Catalyzed Decarboxylation of Phenylcyanoacetic acid anions at pH 8.6 and 60.4°  

The results presented by Cramer and Kampe are amplified by the data in Table XII which correspond to a recent investigation of the cyclohepta-amylose-catalyzed decarboxylation of a series of substituted phenylcyanoacetic acid anions (Straub and Bender, 1972). These data differ strikingly 

Solvent Dependence of the Activation Parameters for the Decarboxylation of p-Chlorophenylcyanoacetic Acid Anion at 60.4°  

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