posted by ~christina~ on .
I had to go and do a oxidation- reduction lab where:
I went oxidized borneol with sodium chloride and added 0.360g racemic borneol, 1ml acetone, and .30ml glacial acetic acid. Then I heated and added through the condenser every 4 minutes .5ml 6% sodium hypochlorite.
I then did extraction with the solution using methylene chloride.
Then we washed the organic layer separated out first with sodium bicarbonate, then separated the organic layer and then washed with sodium bisulfate, and after seperating again, the final solution was washed with water and organic layer was again removed and then dried with sodium sulfate.
Then the solvent was evaporated in hot water bath. Product was camphor.
Then the crystals that formed were placed in a flask and 1ml methanol was added. Then .130g of sodium borohydride was added to the solution. (they say add it slowly but I added it all at once...=() Then the solution was boiled and the sodium borohydride was supposed to dissolve. It didn't and I added 2 more ml of methanol and still had sodium borohydride crystals in the solution. ( I think it was to reduce the camphor to isoborneol => final compound)
Then it was decided to just go on without fully dissolving the crystals and the solutin was left to cool. After that, 3.5ml of cold water was added to flask and the crystals that formed were filtered out but of course still contained the undissolved sodium borohydride crystals.
The IR spectrum of the dried crystals showed that there was still camphor in the crystals and I know that was because of the undisolved sodium borohydride which didn't react with the camphor.
I have these questions I have to answer...
Why was the methylene chloride layer was washed with sodium bicarbonate in the procedure for preparing camphor?
I looked but I couldn't find the reason..
Describe how the filtering pipet worked for the second part of the experiment
This is a funny question since I didn't use a filtering pipet.
Does anyone know how I would use it if I did use it in the experiment?
Thanks alot =D
Also I forgot to ask how to get the percent yield.
I'm not sure but I guess I could calculate the percent yield of both camphor produced and isoborneol produced.
What is getting to me is the ratios...
I added the sodium hypochorite and also the glacial acetic acid but I'm not sure what is the limiting reagent or the ratio of the production of camphor to the reagent ratio.
For the percent yield of the isoborneol I know that there is a racemic mix produced consisting of borneol and isoborneol with isoborneol being the major compound. I'm not sure what is the limiting reagent though...
I think that I can use all the reactants and then calculate the theoretical yield of each and then see which is the limiting but I'm not sure once again about the ratio.
I need help with that too...
I'm not up to answering most of the first question; however, I suspect you did not oxidize anything with NaCl. As for the limiting reagent second part, forget about the limiting reagent. All of the glacial acetic acid, hypochlorite, sodium borohydride and those other things you added don't go into the theoretical yield and they were there in excess. The yield comes from the starting material of borneol. And the final product is the product you were trying to get. You CAN calculate two percent yields if you wish but I suspect your prof wants the overall yield. The first would be the yield for camphor and the second would be the yield from camphor to isoborneol.
Back to the NaHCO3 thing, don't you think this is to neutralize the excess acetic acid?
Oh..so that's what it was for...
I guess I didn't think of that.
I suspect you did not oxidize anything with NaCl
No I didn't use NaCl at all in this lab.
You CAN calculate two percent yields if you wish but I suspect your prof wants the overall yield. The first would be the yield for camphor and the second would be the yield from camphor to isoborneol.
I wasn't told what he wanted..just I assumed I had to find the percent yield since we aren't weighing the product for nothing. Other people sounds surprised however that we have to find the percent yield after a experiment. (I learned in quant that of course you have to find the ammount of product you have if you have product that is weighable => you'd think this was common sense)
Thanks very much for replying to my post Dr.Bob =D
darn..forgot to take off bold..but if you look at it I think you can see which is your post (first 2 separated sentences)
Yes, I got it ok. I think you would be safe if you calculated the overall yield. As for the NaCl, I guess that was a typo for in the first sentence you say "I went oxidized borneol with NaCl and added...."
Typo's are a hazard.
I think I got confused and typed NaCl instead of the sodium hypochlorite.
Thanks for your help Dr.Bob =D