Electronic Substituent Effects in the Nitrilase-Catalyzed Hydrolysis of Para-Substituted Benzyl Cyanides

Article abstract of DOI:10.1016/S0040-4020(01)80205-2

The initial rates of the nitrilase (Novo)-catalyzed hydrolysis of a series of para-substituted benzyl cyanides (R = NO2, Cl, OCH3, OH, NH2) were found to be susceptible to the nature of the para-substituent of the substrate and a Hammett-type linear free energy correlation was observed with ρ = 0.96.In a separate study, effective solubilization of substituted benzyl cyanide substrates having electron-donating groups (OH, NH2, OCH3) was achieved upon mixing with β-cyclodextrin to form 1:1 mol ratio inclusion complexes, but para-substituted benzyl cyanides with electron-withdrawing groups (Cl, NO2) were not fully solubilized under the same conditions.In addition, it was shown that the presence of β-cyclodextrin not only had no inhibitory effect on the enzyme activity, but it actually increased the initial rate of hydrolysis of the unsubstituted benzyl cyanide:β-cyclodextrin inclusion complex.However, the initial rates of hydrolysis were observed to be smaller when β-cyclodextrin was added to the para-substituted benzyl cyanides.