Kinetic analysis using the example of the hydrolysis of pNPA

Kinetic analysis using the example of the hydrolysis of pNPA

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Hydrolysis of pNPA


During the hydrolysis of the ester pNPA (p-nitrophenyl acetate, acetic acid p-nitrophenyl ester)

can increase the concentration of the H2O regarded as constant and the evaluation carried out according to the 1st order.

Measured variable extinction

The extinction can be used as a measured variable, since this represents a concentration-proportional variable according to Lambert-Beer’s law. However, there are advantages and disadvantages:

  • Spectroscopic measurements in the UV / Vis range are very accurate and are relatively easy and quick to obtain.
  • The Lambert-Beer law gives total information about all substances absorbing in the solution. The concentration-time differential equations must be converted into equations using the measurement signal absorbance.

Since the ester and the phenol differ in their spectroscopic properties, the hydrolysis for determining the concentration is monitored spectroscopically with the aid of multi-wavelength measurements. The reaction spectra obtained allow a statement to be made about the course of the reaction.

Video: PNPACAT Online Mock Test. InspireHub (August 2022).