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Topic: Differentiating the sulfide from the ether product  (Read 3534 times)

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Offline JustaNovice

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Differentiating the sulfide from the ether product
« on: August 18, 2011, 05:31:19 PM »
I'm trying to figure out how to determine the which of my fractions is the product I want. I know I have both the sulfide and the ether in my crude product. However, I do not have the press to make a KBr and my adviser doesn't feel spending the money is "worth while". Be what it may, that's reality. Similarly, I have tried to dissolve the separate products in DCM, drop three or four drops of the solution on a KBr plate, let it evaporate, and get the IR spectrum, unsuccessfully. I've also found suggestions such as Nujol mull, but I don't have a means for analyzing a sample that way I don't believe. Does anyone have any suggestions? Does anyone know an outside company that would accept a sample and provide me with the IR of my products? All I need to see is the -OH stretch.

My reaction scheme is below.

Offline Honclbrif

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Re: Differentiating the sulfide from the ether product
« Reply #1 on: August 18, 2011, 06:56:13 PM »
Both your starting material and your product will have a phenolic OH stretch, as this group is unaffected by the reaction. What you should be looking for is the disappearance of the SH stretch.

A quick and reliable way to determine the progress of your reaction is by TLC. Chemical stains may also be your friend in this case. Permanganate stain in particular goes nuts over anything with sulfur in it.
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Offline nox

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Re: Differentiating the sulfide from the ether product
« Reply #2 on: August 18, 2011, 08:25:01 PM »
Are you sure the product is supposed to have a de-aromatized pyridine ring?

Offline JustaNovice

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Re: Differentiating the sulfide from the ether product
« Reply #3 on: August 18, 2011, 09:15:42 PM »
Thanks, Honclbrif, for the permanganate suggestion, I wasn't aware it reacted so well with sulfur. So I stain it and the heat it I'm assuming? The TLC shows three separate products and because of the similarity between the thiol and phenolic alcohol, I assumed I had both the sulfide and ether in my product.

Nox, I have the 1H-NMR, 13C-NMR, DEPT, as well as a COSY which verify the pyridine is nonaromatic. I reduced the ring with NaBH4, which I now realize I didn't include in the scheme. My apologies.

Offline Honclbrif

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Re: Differentiating the sulfide from the ether product
« Reply #4 on: August 18, 2011, 09:27:05 PM »
I'd run a column on it, collect the various spots, and discard the ones which correspond to your starting material. With all that NMR data you should be able to determine which compound is which. Phenol OH proton shows up around 5 ppm, thiophenol SH proton shows up around 3. At this point IR is just icing on the cake.

What was the issue with the IR? Was the compound insoluble in DCM, or were you just getting a bad spec for other reasons?
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Offline nox

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Re: Differentiating the sulfide from the ether product
« Reply #5 on: August 18, 2011, 09:51:03 PM »
Look at the shift of the vinyl proton in your NMR. 

The product you want has a vinyl sulfide, and according to my Reaxys search, a similar structure (cyclohexyl ring instead of reduced pyridyl ring) has the vinyl proton show up ~6 ppm.

I think if you made the enol ether instead, the vinyl proton would be somewhere around 5-5.5 ppm, so hopefully that should be enough to distinguish the two.

Offline JustaNovice

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Re: Differentiating the sulfide from the ether product
« Reply #6 on: August 19, 2011, 10:15:17 AM »
Thank so much for the suggestions.

I'm going to exactly what you both suggested.

Honclbrif, the problem I was having with the IR is that even though my product was soluble in DCM, I couldn't get a spectra from the IR for whatever reason. I tried several times with varying concentrations of my product to get a thin film to form on the KBr plate so I could get a spec, but it wasn't working. In speaking with the guys running our spec lab, they had never seen anyone try get a spectrum that way, so I'm not really surprised I couldn't get a spec.

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