Question

Please help?!?!

When ACE. ASP and CAF were analyzed by TLC using 2:9:9 mixture of t-butyl alcohol. 4-methyl-2-pentanone and ethyl acetate respectively the following R_f values were obtained: ACE (0.51), ASP (0.15) and CAF (0.35). These results are not the same ones obtained when using 2percentage acetic acid and 98percentage ethyl acetate as the mobile phase? Explain why were the results different for our case (TLC shown) particularly for caffeine. Give the R_f values you obtained in lab for the compounds extracted in last week's lab (benzoic acid, 2-naphthol and naphthalene). Were all the compounds pure? Were there any impurities in any of the solids obtain. Which of the solids was the purest and which was the least pure based on the TLC?

Answer 1

4. When we uset-Butyl alcohol, 4-methyl-2-pentanone and ethyl acetate all these solvents are inert in nature with ACE,ASP and CAF so we get respective spots on TLC.

Suppose if 2% acetic acid and 98%ethyl acetate we use acetic acid, CAF will react with acetic acid to form salt and there is no ellution on TLC.

5. If it is single spot then we can say that that related compound is pure.