Why must Rf values be quoted along with the specific solvent system used for the TLC experiment concerned?
Why must Rf values be quoted along with the specific solvent system used for the TLC...
For TLC plate separation, why do we use Rf values instead of distance measurements (e.g. the spot travelled 5 cm from the starting line)? What would happen if we compared solvent systems using distances rather than Rf values?
If acetaminophen is used in a TLC experiment with 100 % ethyl acetate as the solvent system, explain in terms of polarity why the spot would move fast or slow up the TLC plate?
Two compounds might have spots with the same Rf value in a TLC experiment and not be identical compounds. Which proposed TLC experiment could best help determine whether the compounds are identical? Select one: Repeat the original experiment with a mixture of the compounds in a single spot Repeat the original experiment with larger spots of each compound Repeat the original experiment with a different solvent system Repeat the original experiment with the development chamber jar open
2) During silica gel TLC analysis, when 2-propanol was used as a developing solvent, two substances moved with the solvent front (Rf = 1.0). Can you conclude that the substances are identical? If not, what additional experiment(s) would you perform? (5 pts).
4. TLC Data: Provide a drawing of your TLC plate with proper labels, and specify which solvent system was used to develop the TLC. Comment on the purity of your product according to TLC. Explain why the newly produced phenacetin would run higher on the TLC plate compared to the starting material acetaminophen.
3. If the TLC plate development had stopped before the solvent front reached the top of the TLC plate (i.e. maybe it reached the middle of the TLC plate when it was stopped, instead): a) Would the Rf values have been affected? If so, how? If not, why not? Give a numerical example to support your answer. b) Would the size of the spots have been affected? If so, how? If not, why not? (Hint: think about the diffusion of...
3. TLC analysis of an unknown sample using pure ethyl acetate as a developing solvent gives a single spot with an Rf value of 0.08 1 points A. Explain why this result does not guarantee that the sample is a pure compound. B. Suggest two changes that could be made to the experiment to improve the analysis of the unknown sample. 2 points Change 1 Change 2
1. Calculate the Rf values for spots A and B on the TLC plate drawn below. Based on the Rf values which compound (A or B) is most likely to be more polar? a. Calculate Rf values for A and B b. Which compound A or B will most likely be polar? Why?
When 2-propanol was used as the developing solvent, two substances moved with the solvent front (Rf = 1) during TLC analysis on a silica gel plate. Can you conclude that they are identical? If not, what additional experiments(s) would you perform?
Why is there a direct correlation between the dielectric constant and the Rf value during a TLC analysis? What is the relationship between the solvent polarity and the Rf values? Why are some solvent mixtures better at separating compounds than others?