Pressure Effects on the Stereospecificity of the Cleavage of Phenyl Acetates Catalyzed by α-Cyclodextrin

Article abstract of DOI:10.1021/j100220a019

The rate of meta and para specific hydrolysis of three phenyl acetates catalyzed by α-cyclodextrin was measured at pressures up to 2 kbar at 25 deg C in 0.05 M Tris buffer solution.The substrate binding constants (K) and the rate constants for the acylation process (k₂) increased monotonically up to 2 kbar.From the pressure dependence of K, the volume changes (ΔV) accompanying the formation of the inclusion complexes at 1 bar were -16 +/- 2 cm³/mol for mNPA, -10 +/-2 cm³/mol for mMPA, and -1 +/- 2 cm³/mol for pMPA.The activation volumes (ΔV^*) for the cleavage of ester molecules in the acylation process were -9 +/-2 cm³/mol for mNPA, -12 +/-2 cm³/mol for mMPA, and -17 +/- 2 cm³/mol for pMPA, respectively.The meta and para stereospecific accelerated cleavage is discussed via the volume parameters for the hydrolysis of meta-substituted compounds catalyzed by α-cyclodextrin and compared with those for the para-subatituted ones.