Organic Chemistry Laboratory I CHEM 221
Name: Lab Day:
Worksheet : Thin Layer Chromatography (TLC)
1. A student carries out the following reaction on O O
salicyclic acid in the laboratory. She decided
to follow the course of the reaction by thin OCH3
layer chromatography. Assume that her
solvent system was chosen so that the OH OH
salicyclic acid and methyl salicylate give Salicylic Acid Oil of Wintergreen
different R f values. Sketch reasonable TLCs
that would be expected at the beginning (i.e., only salicylic acid is present), when the reaction
is in progress (both salicylic acid and methyl salicylate are present), and when the reaction i s
complete (only methyl salicylate is present). Be sure to label the spots appropriately and have
the correct relative Rf values.
x x x
aliquot from aliquot from aliquot from
beginning of middle of end of
reaction reaction reaction
2. The purity of a compound was tested by TLC, and with a particular solvent system one spot was
seen with an Rf value of 0.05. However another test (melting point) showed that the compound
was not pure.
a . What was wrong with the TLC experiment?
b. What should be done so that the impurities are detected by TLC? Be specific.