Question

1. A student calculated the R(f) value for a spot to be 1.05. Why is the value wrong?

2. The progress of a reaction can be followed using TLC as follows: Several TLC plates are prepared by spotting them with the starting compound(s) and the product(s). (each plate is spotted with all the compounds,each in its own spot.) A place on each plate it saved for the reaction mixture.Periodically as the reaction proceeds (for example, every 30 minutes) a prepared plate is spotted with the reaction mixture, and then it is developed and visualized. By comparing the TLC’s, one will see that intensities of the spots in the reaction mixture change as reactants are consumed and products form. (note the R(f) value of the spots do not change; only the intensities change.)

   1. Make a sketch of what you would expect the first TLC plate would look like after it is developed. Make two more similar sketches that would show what the TLC plates would look like when the mixtures were tested at 45 and 90 minutes. (Hint: Remember that there is no product in the reaction mixture at the start)

   2. What TLC result would show that the reaction was complete?

Answer 1

Last TLC which would show only single spot of product (not Reactant spot ) be indication for completion of Reaction . BUT SPOTTING HAS TO BE DONE FROM reaction Mixture .