what is thin layer chromatography (TLC) least useful for from the list below?

a. to establish that two compounds are identical

b. to determine the number of components in a mixture

c. to determine the appropriate solvent for column-chromatographic separation.

d. to determine if crystallization or distillation ma by more effective for a separation.

e. to monitor a column chromatographic separation

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Reid WolffLv2

17 Dec 2019

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These questions are from an experiment where we had a mixture of Ferrocene, acetylferrocene and diacetyl ferrocene and we separated each by using column chromatography. Before doing the column chromatography we did TLC analysis to ensure that we did, in fact, have a mixture of these 3 compounds.

During the column chromatography we first eluted the ferrocene using pure hexane. Then we eluted the acetylferrocene using a 1:1 mixture of hexane and methylene chloride. Then we eluted the diacetylferrocene using a 9:1 mixture of hexane and methylene chloride.

1. Rank ferrocene, acetylferrocene, and diacetylferrocene in order of increasing polarity. Do the TLC results from your fractions support this ranking? Explain.

2. Rank the solvents used in the experiment in order of increasing polarity.

3. Why do you start with the least polar solvent/solvent mixture and progress to increasing polar solvent/solvent mixtures when eluting the ferrocene compounds from the column rather than starting with more polar solvent system and progressing to less polar solvents?

4. How do the thin layer and column chromatography for this experiment compare in regard to stationary and mobile phases?

5. What key feature in the IR spectrum of acetylferrocene distinguishes it from the spectrum of ferrocene?

An unknown mixture was analyzed using TLC on a silica gel plate and developed in 1:6 ethyl acetate:hexane, and gave 2 spots with Rf values of 0.6 and 0.5 respectively. 1)Would this be considered a good separation between the two? Briefly explain. 2)Which spot represents the more polar compound(s)? 3)Can you say for sure how many compounds are contained in the mixture? If so, how many are there? Briefly explain. 4)If not, what further conditions might be performed to determine the number of components in the mixture or to obtain a better separation? Explain. 5)Suppose you carry out a TLC separation of acetaminophen and aspirin on silica gel using a nonpolar eluting solvent, hexane. Which should have the larger Rf value? Briefly explain. 6)What are the methods for "visualizing" spots on TLC plates that we will use in this lab?

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