In running TLC under the following conditions, you get results that are less tha

Question

In running TLC under the following conditions, you get results that are less than ideal. Consider the situation in each case and suggest a correction.

(a)You run TLC on a mixture of two unknown halogenated alkenes , but you see only one spot with an Rf of 0.91. The solvent used was ethyl acetate.

(b) You run TLC on a mixture of thiol and an amine, and you get only one spot with an Rf of 0.15. The solvent was a mixture of petroleum ether and dichloromethane.

(c) When you put your TLC plate in the developing chamber, the solvent in the chamber covered the spots on the TLC plate baseline.

Explanation / Answer

a,Rf of 0.91 suggests that the polarity of the solvent used is too high. Ideally, Switch to a solvent of lower polarity, such as dichloromethane. If the Rf is still too great, employ a low-polarity co-solvent such as hexane, i.e. use hexane-dichloromethane solvent pair.

b,use polar solvents like alcohols because the thiols and amines are highly polar

c reduce the amount of solvent in the chamber

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