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Topic: Sticky compound  (Read 2846 times)

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Offline PriyaP

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Sticky compound
« on: March 02, 2017, 04:24:45 AM »
I am doing a Williamson ether synthesis reaction between two aromatic molecules. For this I have tried numerous literature procedures and each time I get exactly same TLC with no starting materials and a clear new spot (which I assume is the product). However the product is very sticky and resin like in nature (both the starting materials are free flowing powders), due to which I am not able to obtain a clear NMR. NMR spectra looks very messy and unreadable. Can anyone please suggest how must I proceed to get a clear NR spectrum.

Offline hypervalent_iodine

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Re: Sticky compound
« Reply #1 on: March 02, 2017, 07:09:47 AM »
Have you purified it by column, or is the NMR you are running of the crude?

Offline AWK

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Offline Irlanur

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Re: Sticky compound
« Reply #3 on: March 03, 2017, 03:38:14 AM »
Quote
However the product is very sticky and resin like in nature (both the starting materials are free flowing powders), due to which I am not able to obtain a clear NMR.

if it's resin like there is no way you're going to get a nice NMR spectrum, at least not with liquid-state Probeheads. There might be a chance to get a spectrum if you have a solid-state NMR, but this also depends on "how sticky" your compound is. Also it is unlikely that you will get a nice proton spectrum (http://u-of-o-nmr-facility.blogspot.ch/2008/03/1-h-nmr-spectra-of-solids.html);

If you want a very nice NMR you'll need to dissolve it somehow.

Offline wildfyr

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Re: Sticky compound
« Reply #4 on: March 03, 2017, 12:32:48 PM »
Sounds like whatever you made polymerized. Broad NMR peaks are a classic sign of polymerization, as is insolubility and the state of manner known as "goo." Welcome to organic chemistry.

Are you sure you have one clear, non streaking TLC peak? Check the other wavelength on your UV source and see if it shows anything.

Offline vikram

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Re: Sticky compound
« Reply #5 on: April 21, 2017, 02:24:02 AM »
I agree with whatever wildfyr said above.

Try to dissolve the compound in minimum amount of Ethyl acetate and then slowly try to precipitate it using hexane.

Usually above method works. In my case compound was getting sticky due to extensive hydrogen bonding.

Alternatively, you ca try dissolving in acetonitrile and rotaevapourate then.

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