Question

How is the progress of reaction followed in the following first order reaction:

Inversion of cane sugar?

Answer 1

The inversion of cane sugar (sucrose) is a first-order reaction:

\[\ce{C12H22O11 + H2O −> [H+]C6H12O6 + C6H12O6}\]

The progress of this reaction is followed by measuring the optical rotation of the solution using a polarimeter.

Sucrose is dextrorotatory

Fructose is strongly levorotatory, and

Glucose is dextrorotatory

As the reaction proceeds, the overall optical rotation changes from positive to negative.
This change in optical rotation over time is used to monitor the rate of reaction and determine the rate constant.