Student A did not see any spots on her TLC plate after visualization under iodine vapor. Which of the following is her best course of action? Adding more solvent to her sample Repeat the experiment, this time increasing the number of times she spotted on the plate Using heat to activate the plate Returning the plate to the iodine chamber and waiting a few more minutes Previous

Student A did not see any spots on her TLC plate after visualization under iodine vapor. Which of the following is her best course of action? Adding more solvent to her sample Repeat the experiment, this time increasing the number of times she spotted on the plate Using heat to activate the plate Returning the plate to the iodine chamber and waiting a few more minutes Previous

Macroscale and Microscale Organic Experiments

7th Edition

ISBN:9781305577190

Author:Kenneth L. Williamson, Katherine M. Masters

Publisher:Kenneth L. Williamson, Katherine M. Masters

Chapter8: Thin-layer Chromatography: Analyzing Analgesics And Isolating Lycopene From Tomato Paste

Section: Chapter Questions

Problem 10Q: A TLC plate showed two spots with Rf values of 0.25 and 0.26. The plate was removed from the...

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Of Aspirin, ethanol, acetaminophen, ethyl acetate, hexane, and water which could go undetected during HPLC analysis, but could result in a lower than expected melting point, why are they not detected by HPLC analysis?
1.Why are the chlorophylls less mobile than the carotenes on the TLC plate? Give athorough explanation, including a sketch of how each type of molecule would interactwith the silica stationary phase material (you can use schematic structure formulas, ratherthan draw the whole molecules, which are quite large!). For instance, would one of thosetypes of molecules create more intermolecular force interactions than the other?
What happens when the level of the eluent solution in the developing chamber (beaker) is adjusted to fully submerge the origin line of the TLC plate? (in the analysis of sample using TLC)
a) Suggest ONE(1) way elute Compound C if it could not be collected with the above solvent system. b) What is an alternative of adsorbent to silicon oxide that can be used for this analysis? State ONE(1) similarity between those adsorbents. The following figure shows column chromatography analysis of a sample developed in a mixture of hexane-ethyl acetate (1:1) using silicon oxide as a stationary phase.
In which of the following scenarios might you expect the observed melting point to be depressed? Choose all that apply. a. The heating rate for measuring the melting point was set too high. b. The percent recovery of recrystallized solid was less than 100%. c. A solid that was recrystallized from hexane was filtered and dried without washing with additional hexane while it was on the filter funnel. d. A solid recrystallized from toluene was left on the filter funnel for only a short time before its melting point was measured. e. The melting point capillary tube was packed with too much material.
Vaccum filtration is the major technique used in this experiment. The following step sequences are recommended: 1) turn on vacuum 2) wet the filter paper and 3) pour the product solution into the buchner funnel. can the Vacuum be turned on in the last step instead?explain
What are the possible reasons why there are no spots on the Developed Plate after analysis?
Which of the following cannot be used as adsorbent in column chromatography? a. Silica gel b. Magnesium oxide c. Alumina d. Potassium permanganate
28. In addition to what is not a characteristic of gas chromatography as listed in the probelm can you give the general characteristics of Gas Chromatography?
a) What would you see if you ran a Thin Layer Chromatography (TLC) on a mixture of the three solids shown below using silica gel as the stationary phase and ethyl acetate/hexanes as the mobile phase? Whichsolid would have the highest Rf and which would have the lowest Rf? Explain b) Would changing the mobile phase (from part a) and increasing thepolarity by introducing small amount of methanol to the mobile phase change the order ofRf of the above 3 compounds? Explain c) Another type of chromatography is Reverse Phase Chromatography. In this type ofchromatography, the stationary phase is non-polar and the mobile phase is polar. If astudent performed Reverse Phase TLC on the mixture of 3 solids (from part a),what would be the order of Rf’s of the compounds? Which would have the lowest Rf andwhich would have the highest Rf?
In recrystallization, fluted filter paper is used instead of a regular cone because it minimizes its contact with the glass funnel. Why is this important?
Silica gel (stationary phase) can potentially interact with analytes by what intermolecular forces?