Lab Report 2: Excedrin Guidelines

[ks...@cornell.edu]

Hey everyone,

I apologize this is coming a little later than I intended, but hopefully this will be helpful in figuring out what to include in your next lab report. There was an overabundance of things to do on Monday so I understand that not all analytical tests (MP, TLC, IR) were performed by everyone. I am hoping that between the whole class though, there is enough information to pool together to write an effective lab report. So here are some things I will be expecting to see in the report:

1.) TLC analysis: I believe most people ran a TLC of the standard solutions and the excedrin mixed in ether. Technically this was for Part II of the experiment (column chromatography), but if this is the only TLC plate you have, then analyze this TLC plate. Since you guys just recently wrote a report on TLC, I'm not looking for excruciating detail on it, i.e. I don't need the theory on how TLC works. What I'm looking for is comparison of the Rf values, relative polarities of the constituents and the developing solvent used for the TLC. Also, a depiction of the TLC is not required for this report (or future reports), but if you want to include it that certainly helps me visualize your results. If you did manage to run a TLC of the components you isolated yourself from the extraction, please include that and analyze it! 

2.) Melting Point analysis: I know there are a number of you who did not take melting points, but I'm hoping enough of you did and that you are willing to share this information. Remember, wide melting point ranges and depressed values indicate an impure sample. If the melting point is much higher than what you'd expect, then the compound you have is something different. If your compound did not melt even at super high temperatures, then you have to think about what you actually have. Melting points will be helpful in determining whether the extraction worked well or not, so use that data to strengthen your argument.

3.) IR analysis: I believe only a couple people actually got spectra for these compounds. If you did and you're willing to scan it onto the email chain, that would be pretty awesome! But I understand if that may be difficult to do, so if you did acquire spectra, use it in your analysis and try to identify the major peaks. If you did not acquire spectra, then what I want you to do is find a standard IR spectrum for acetaminophen and interpret the major peaks. There is a Japanese database where you can find the spectrum; just type SDBS into google and click on the first thing that comes up. You might be wondering what are considered to be the "major peaks?" You only need to identify the stretches of the major functional groups in the molecule. So carbonyl stretches are a big one (esters, amides, carboxylic acids, etc.) as well as any alcohol stretches which are pretty characteristic. You will also want to look for any C-H stretches whether they be part of an alkane or an alkene (or alkyne). Write down the values in your results section and discuss the identification process in your discussion. This will be good practice in interpreting IR (which will be helpful since all future reports will include discussing IR). 

4.) Yield: Show calculations for how you would get the yield. If you didn't calculate it, that's okay, but make sure to discuss yield and all the pitfalls where you could lose yield and such.

5.) Discuss the extraction and think about what issues you encountered and why this extraction didn't work particularly well (for most people anyway haha). So basically, a little theory on extraction would be good as it pertains to your discussion of the results. So I don't need super detail on extraction theory, but if you're trying to make a certain argument about why things happened the way they did, you should invoke some theory as needed. So what I'm looking for is ideas as to where the compounds went during the extraction. Why did most people not get acetaminophen? Where did it go? I will give you a hint for why this extraction had issues: solubility! Think about it, and try to come up with a good discussion.

I hope all of this helps. Good luck, and if you have any questions feel free to send me an email! Also, my office hours are today in Baker 158 from 2-3pm. I haven't had many takers yet (no one actually lol). I don't know if I picked a crappy time for office hours, but if I did, let me know and we'll try to figure out if there's a more convenient time for everyone. 

Best,

Kyle