This is for ochem lab. please answer questions 1 and 2. Explain Questions When 2

Question

This is for ochem lab. please answer questions 1 and 2. Explain

Questions When 2-propanol was used as the developing solvent two substances moved with the solvent front (R_f = 1) during TLC analysis on a silica gel plate. Can you conclude that they are identical? If not, what additional experiment(s) would you perform? The R_f value of compound A is 0.34 when a TLC plate is developed in pentane and 0.44 when the plate is developed in diethyl ether. Compound B has an Revalue of 0.42 in pentane and 0.60 in diethyl ether. Which solvent would be better for separating a mixture of A and B by TLC? Explain.

Explanation / Answer

1. In 2-propanol, the compounds A and B move with solvent front. We cannot conclude that they are identical. We can re run the TLC in a different solvent sysyem such as mixture of ethyl acetate and hexane and check that they have same or different Rf values.
2. In pentane, the difference in the Rf values of compounds B and A is 0.42 - 0.34 = 0.08. In diethyl ether, the difference in the Rf values of compounds B and A is 0.60-0.44 = 0.16. Since, the difference in Rf values in diethyl ether is almost double the difference in Rf values in pentane, diethyl ether is better solvent for separation by TLC.

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