Question

9. Based on looking at your TLC plate taken during step 2 of Dilantin synthesis, answer the following questions (a) Which is more polar, benzoin or benzil? Circle Below. Benzoin Benzil (b) Now look at the structures of benzoin and benzil. Specifically explain why one of these compounds has a lower Rr value than the other. You must address structure in your answer. Explain in one or two sentences (c) How can you tell by TLC if your reaction went to completion? Explain in one sentence 14. Without looking at a TLC plate, do you think Dilantin should have a higher or lower Rr value than the starting material, benzil? Circle Below. Explain your reasoning. Dilantin has a Higher Rf valueDilantin has a Lower Rf value Explain in one sentence:

Answer 1

9A.Ans

benzoin is the more polar because that hydroxyl group has a charge differential between the oxygen and hydrogen.

benzoin with high level of symmetry in the molecule cancels out any overall dipole and leaves the molecule non-polar.

9B Ans.

Rf is the "Retardation Factor", which is the ratio of the distance traveled by a compound in a mobile phase compared with the distance traveled by the front of the mobile phase itself.

However, the compounds migrate differently depending on the type of mobile phase used because the migration speed depends on some characteristics of the solvent, such as polarity. The Rf value is characteristic for any chemical compound.

when we compare Rf values for Benzil and Benzoin in a non-polar solvent,obviously the Benzil exhibit high Rf..

Because Rf depends on the Nature of Compound and solvent..If both non-polar then that compound will have high Rf than other

9C

compare the spot of the starting materials to the spot of the reaction mixture. When the spot of the starting materials doesn't appear at the same position as the starting amterial spot (or nearly gone, if the other reagent is in excess), you're done.