This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Austin Thai Chem 3AL, Sec. 103 GSI: Rob Padilla March 24, 2010 Experiment 7: Thin Layer Chromatography Discussion For the TLC solvents, narrowing down the potential solvents to use for Part 2 was achieved by observing which TLC plates from each solvent was most consistent and held spots that werent all over the place. The most ideal plates were those that had spots separated from each other in almost its own rows, and that exhibited some sort of separation and not closeness of any sort. TLC plates that exhibited spots too close to each other, or those that didnt have spots at all due to it being under the spotting line, were not ideal and not part of our criteria. In general, we needed to find the plates that showed the greatest separation, and above all, plates that didnt show up as close to each other as possible. From this, we found that our best solvents were the 92:8 ethyl acetate:acetic acid and 60:40 hexane:ethyl acetate. After determining the top two solvents that our group could use for Part 2 of the experiment, we then applied the TLC plates with two known compounds and the unknown pain killer, to a total of 4 plates with the two TLC solvents we had. Therefore, for each TLC plate, the first spot would be a known, such as aspirin, the second the unknown pain killers, and the final spot the known, such as acetaminophen, and would be tested and seen via the 92:8 ethyl acetate:acetic acid solvent. From there, four TLC plates were created and we then compared each one. The unknown painkillers spot in all four were nearly consistent with each other at a specific area on the plate, which was around the upper-middle area, mainly around the 40mm zone. It also is consistently located around the third row horizontally, which is where ibuprofen was found in Part 1 of our experiment previously. Therefore, we established the conclusion that the unknown was ibuprofen, which proved correct. By comparing the TLC plates in Part 2 with those of Part 1, we could establish an identity for the unknown and its spots with the known spots that we found previously. The Rf values that we predicted for the four compounds/painkillers were, compared to the actual Rf values gained from the experiment, 50% correct and 50% wrong. For aspirin and acetaminophen, I assumed the average of their values each were 0.6 and 0.3 at first. After the experiment was done, the values found were close and estimated about the same, such as 0.57 for aspirin in 100% ethyl acetate, compared to my aspirins Rf value of 0.6. The latter half (ibuprofen and caffeine) were complete opposites of what they were, as caffeines Rf was around 0.2-0.3 instead of my prediction of 0.7 range, whereas caffeines Rf was around 0....
View Full Document