ChemNEWBIE1320
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Bimolecular nucleophilic substitution; what went wrong?
Ok, so most of you should be able to come up with a quick answer for me.
-What exactly went wrong?
Last week I preformed an SN2 reaction in the lab. Attached is the specific handout. Anyway, theoretically I'm getting that I should yield close to
1.59*10-3 mol of product, but this does not seem right to me. Also, experimentally I have produced a much greater yield (>1g) than this
which is what's throwing me off.
I am aware of the enolates formed, and am wondering, did the reaction just did not proceed to completion and the excess weight was resultant of the
iodine bound molecule? Or am I'm just terrible at math and I did something screwy with my theoretical yield?
I'm going nuts here. Please help!
-Newbie
Attachment: SN2Lab.pdf (128kB)
This file has been downloaded 1074 times
[Edited on 21-10-2013 by ChemNEWBIE1320]
[Edited on 21-10-2013 by ChemNEWBIE1320]
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ChemNEWBIE1320
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Ok, given the weight of all reagents used, the only way I can account for the exponential yield is if the product was not completely dry when
recording my final mass (residual MeOH), it had not proceeded to completion, or I had picked up something from a dirty RBF. After adding up all of the
masses of reagents; even if all of the initial sodium hydroxide and iodine were still present in my final product, there would still need to be at
least 0.65 mL MeOH in my product.
Anyone have a better conclusion than that?
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Lambda-Eyde
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You're sure you didn't do something incredibly stupid, like weighing your boiling chip or drying agent together with the product?  Other than that, I can't see any other possibilities than residual solvent or
weighing errors.
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ChemNEWBIE1320
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I know for a fact that there was no drying agent present. The boiling chip on the other hand.......haha It's been a few days and I do remember
scraping a big chip out of there after the first filtration but it definitely is possible that another smaller piece could have been added initially
and later unaccounted for.
Since I did wash the product, there shouldn't have been any residual iodione or sodium hydroxide and that would mean that there was actually quite a
bit of methanol left which probably wasn't the case either. So....unfortunately, I think you are correct Lambda. lol live and learn I guess.
[Edited on 21-10-2013 by ChemNEWBIE1320]
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