Kinetics of Crystal Violet    

CV+   +   OH-                     CV-OH

   

electrostatic potential                     electrostatic potential

crystal violet ion (CV+)                          colorless product (CV-OH)

trigonal planar carbon        CENTRAL CARBON        tetrahedral carbon

Press the buttons to examine the electrostatic potential maps for each molecule.

In CV+ the central carbon (sp2) has a p orbital that allows interaction between the three rings (blue/purple color of electrostatic potential map).  This electron interaction does not happen in CV-OH, hence the loss of any color of the solution.

As the reaction of crystal violet proceeds, what happens to the absorbance of the solution in the reaction vessel?  Sketch the graph (click on graph for answer).

For ideal interaction of the pi cloud electrons from the rings across the central carbon, the CV+ structure would be planar.  View this possibility below and describe why the rings on the CV+ twist.

space filled        electrostatic potential

The electrostatic potential map shows how the rings interact across the central carbon.  Structures of CV+ and CV-OH were produced in Spartan '02 and AM1 stabilized.  The twist angle of the rings in the CV+ agrees with x-ray measurements.

Back to CHM 103 webpage.

Scott A. Sinex        Prince George's Community College        8/2003