The lab is TLC Separation of Fluourenone, Fluorenol, and Fluorene. We are using

Question

The lab is TLC Separation of Fluourenone, Fluorenol, and Fluorene. We are using silica gel. Numbers 3-5 of the prelab questions I don't understand. We hardly received any background information so please explain! PROCEDURE Determination of the optimal solvent mixture A solution of the mixture of three compounds (labeled M) is spotted onto each ofthree TLC plates and a plate is each of the following three solvents. is very important to spot as little material as possible to minimize overloading and spreading as the plate develops. (It is not necessary for each student to run every plate. You may work in pairs for this part.) Sketch each resulting plate in your notebook 1) 9 mL hexanes: 1 mL ethyl acetate (9:1) 2) 8 mL hexanes: 2 mL ethyl acetate (4:1) 3) 5 mL hexanes: 5 mL ethyl acetate (1:1) From a comparison of the three plates, it may be possible to choose a mixture that gives the best results. Alternatively, you may decide to try a solvent combination in a ratio between two of the above. Identification of the components of mixture M Mixture M is spotted on a TLC plate along with solutions of each of the standard compounds (F- ONE, F-OL and F) on one wide TLC plate, which is then developed in the preferred solvent mixture that you previously determined.

Explanation / Answer

Pre lab

1) The side where SiO2 layer is on the tlc plate is used to spot the mixture.

2) The tlc plate is dried in air after it is removed from developing chamber and then moved to indicator chamber which could be an iodine stain.

3) Hexane : ethylacetate = 5 : 5 ratio is most polar as it has highet percentage of polar ethylaceate in it.

4) Hexane is hydrocarbon only and is thus least polar < Ethylacetate is an ester and is thus medium polarity < SiO2 has surface -OH groups which makes it most polar.

5) F-OL with -OH bonds can form strong hydrogen bonds. F has only dispersion forces in them and is the weakest.

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