Organic chemistry lab: Thin layer chromatography (TLC) 1. What would be the resu

Question

Organic chemistry lab: Thin layer chromatography (TLC)

1. What would be the result if the following errors were made in a TLC experiment?

a) spots too large

b) a solvent with too high a polarity

c) a solvent with too low a polarity

d) you did not mark the solvent front

2. How would you expect R(f) values to change if you went from a hexane-ethyl acetate solvent system to hexane only?

3. Two spots on a TLC plate have very similar R(f) values. Could they be the same compound? Describe a TLC method to determine whether they are the same or different?

4. Calculate the R(f) value for the compounds below.

a) Solvent; distance moved: 25cm

b) Bromothymol blue; distsnce moved: 7cm

c) Nitro-Phthalic Acid; distance moved: 1cm

d) Azulene; distance moved: 5.5cm

e) Acetylferrocene; distance moved: 2.8cm

Explanation / Answer

1) a) if there are more than 1 compond present in sample and spot is large sepration of component will not take place goog they intermix with each other

b) non polar componant not run

c) polar coponant not run

d) we can not mesure distance travelled

2) use of solvent depend on nature of componnd undergo TLC we use hehane as solvent for non polar solvent and

hexane-ethyl acetate for polar compound

3) they are not same slightly diffrence in that 2 compound polarity

4) R(f) value = distance travelled by compound/distance travelled by solvent

b) 7/25 =0.28

c) 1/25 =0.04

d) 5.5/25 = 0.22

e) 2.8/25 =0.112

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