g. The use of Calcium Chloride in the Soap p h. The use of thiamine hydrochlorid
ID: 694979 • Letter: G
Question
g. The use of Calcium Chloride in the Soap p h. The use of thiamine hydrochloride in the formation of Benzoin Sa) In a recent experiment, a student used TLC see the progress of the reaction (45 pts) He obtained these results. The starting material was the 2-bromobenzoic acid. The other was supposedly the product. 3.5c 2.2 em Do you think, the reaction contains the starting material,as well? Calculate the Rf value for both the starting material and the final product obtained . Which is less polar as observed with the results?Explanation / Answer
TLC stands for Thin Layer Chromatography; it is an analytical technique in which we exploit each sample's affinity toward different polar/nonpolar solvents.
We use a stationary phase: a phase which does NOT moves, as the name implies. It is typically the "thin layer" or the "plate". It is commonly to use silica gel plates, which are polar, but any species could be used, such as paper.
We also use a mobile phase: as the name implies, this phase will "move" and will carry along the path all the components from the solvent. Many times, you will be able to split in several components the "mixture" of the sample. Therefore, they can be seen in the stationary phase (plate). Typically, we allow the mobile phase to go up to the "Rfinal" mark, or final reference. This is the distance travelled by the solvent (mobile phase). It starts at solvent level, it is R0, therefore.
Rf = distance traveled by sample / distance traveled by solvent
Then, "Rf" value allows us to understand the affinities of anaytes towards the solvent.
As Rf increases, this implies higher affinity toward the mobile phase ( since it is carried all along the mobile phase)
If Rf is low, this implies a low affinity toward the mobile phase; therefore higher affinity toward the stationary phase, since it sticks to the plate rather than travel upwards.
therefore,
there is only product, since there is no spot in the "reactant" region
most polar --> will be the one with the lowest Rf value, due to stationary phase being polar
this is the product, therefore, the 2-bromobenzoic acid is the least polar of the species
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