Organic Chemistry: TLC

 

Organic Chemistry 

Jihyun Yoo

Did aspirin, acetaminophen, ibuprofen salicylic acid or caffeine travel the farthest up the plate? What was your measured length of travel for that compound? Compare your distance traveled (in cm) with two other groups. Are they  exactly the same? Why or why not? Why is it important to report Rf values and not just distance traveled on a plate?

Ibuprofen moves furthest due to its high polarity interacting with the silica plate. It has an Rf of 0.90, indicating extreme polarity, traveling 5.5 cm. Group 5 (4.6 cm) has a continuous oval shape, suggesting strong adhesion to the TLC plate compared to Group 2 (4.5 cm) with separated shapes. Reporting Rf values is crucial for data uniformity and conformity to the scientific community, providing scalable information on solvent-solute distance.

 

Draw the molecules in order of decreasing Rf value. Based on this information, which is the most polar/most capable of forming strong intermolecular attractions with this silica gel? What kind of intermolecular attractions are possible between this molecule and the silica? Which is the least polar/ least capable of forming strong intermolecular attractions with silica? Is this consistent with your hypothesis? Based on the structure, why is this molecule the most non- polar?

Salicylic acid and Ibuprofen are among the most polar compounds, as indicated by their high RF values. Group 5, displaying an oval shape, exhibits strong intermolecular attraction with the silica gel due to hydrogen bonding. In contrast, caffeine in group 3 is the least polar, consistent with its lower RF value.

Were any of the standards simpure? How do you know? Can you identify any of the impurities?

Yes, the standards were impure because many blotches aligned where the solvent had pushed and pulled the solutes. Group 6 had the most impurities, and I hypothesize that toluene and acetone contaminated the species. Group 1 also shows solute impurities with acetone, as evidenced by a distinct group. 

What was accomplished by viewing the plates under UV light? 

Visualization such as viewing changing colors: Viewing the chromatography plates under UV light provides confirmation that the separation process was successful. The presence of distinct fluorescent spots corresponding to different compounds indicates that the components of the sample mixture have been effectively separated based on their chemical properties.

Why was it necessary to also view the plates in the iodine chamber?

It's important to view the plates in the iodine chamber because the silica contains absorption of polar molecules. Iodine has high vapor pressure and, when a TLC plate is exposed to iodine vapor in a chamber, the plate becomes saturated, turning light brown. The compound spot on the TLC plate will appear as a dark brown spot due to iodine's high affinity for unsaturated and aromatic compounds. Viewing the chromatography plates in the iodine chamber provides confirmation that the separation process was successful. The presence of distinct colored spots or bands corresponding to different compounds indicates that components of the sample mixture have been effectively separated based on their chemical properties.

How many molecules are present in each of the over- the-counter analgesics analyzed(Anacin, Excedrin and Tylenol)? What are the identities of those compounds

They’re two molecules that are present because silica gel competes of the solution in plate TLC2 included #8 and #9) and in plate TLC 1 included #1 and #6. The eulote isolates the polarity from non polar or non analysis molecules such as Toluene and hydrocarbons. 

What is the identity of your unknown analgesic? How do you know? Use as much data as possible to back up your claim.

We have coupled sample 10 was B which is acetaminophen and it was mixed with other solutes(unknown) but they’re most polar because they have longer radians compared to the other species. Silica gel binds to the polar.

Discuss any deviations in the appearance of your plates from what was expected, e.g due to overloading, crooked solvent run, etc. Is there anything you would do differently if you were to run the experiment again?

There was deviation that could be observed in the migration pattern of the solutes. Factors such as overloading of the sample or a crooked solvent run might have led to non-uniform migration distances or distorted bands on the TLC plates. These deviations could impact the accuracy and reliability of the experimental results. If I were to run the experiment again, there are several adjustments I would consider. Firstly, I would take extra precautions to ensure the purity of the standards used in the experiment to minimize the presence of impurities on the TLC plates. This could involve using high-quality reagents and properly storing them to prevent contamination.