Question

2) Besides a large spot and the TLC sample being too concentrated, what two other factors can
cause the developed spots to appear as a streak?

6) In what case would column chromatography be used to purify a desired compound because
techniques like recrystallization, extraction and distillation are not adequate to do so?

7) What will happen to the spots on a tlc plate if you use 2-propanol as an eluent instead of ethyl acetate? what makes ethyl acetate a good eluent?

Answer 1

2) polarity of the compound being separated is also makes the effect on spot streak. More polar compounds shows streaks kind of spots k TLC. The main cause is due to srong affinity of compound to silica makes it elute slow and appear as streak.

Examples are acids and amines.

6) Compounds having difference in polarity can be separated by coloumn chromatography. In addition to, compounds which contains impurities also can be removed by chromatography by simply adsorbing this impurities on silica stationary phase.

7) Here, 2-propanol is more polar in nature compared to ethylacetate. So compounds are eluted very fast. So TLC spots are appear first. So, Rf values are decreased for 2-propanol compared to ethylacetate.