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Topic: Dimer?  (Read 6144 times)

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Offline Messi

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Dimer?
« on: October 30, 2012, 09:11:23 AM »
Hi,

If I have a thioamide, what is the likely scenario that the monomer of the thioamide join together to form the dimer shown below? Is it likely?

How come we don't see such things happen with ketones?

See picture below
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Offline yesway

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Re: Dimer?
« Reply #1 on: October 30, 2012, 10:06:07 AM »
I don't see a Thioamide fct group?!
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Offline discodermolide

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Re: Dimer?
« Reply #2 on: October 30, 2012, 10:16:30 AM »
I think the structure may be more like this picture.
Disulphide bonds are well known.
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Offline Messi

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Re: Dimer?
« Reply #3 on: October 30, 2012, 10:32:52 AM »
Well, I did an NMR of my compound, and my suggested dimer was the compound that was confirmed by NMR.

I was just wondering if such dimers have ever been seen? I was slightly shocked.
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Offline discodermolide

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Re: Dimer?
« Reply #4 on: October 30, 2012, 11:07:47 AM »
What is the chemical shift of the CH protons?
Did you manage to get a mass. spec.?
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Offline Messi

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Re: Dimer?
« Reply #5 on: October 30, 2012, 11:53:33 AM »
Well I sent it to the NMR expert and he ran a DEPT and an HMBC and confirmed that the dimer was the resulting compound!

Did you ever see such things happen when you were working with thioketones?
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Offline discodermolide

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Re: Dimer?
« Reply #6 on: October 30, 2012, 11:57:17 AM »
No, I never saw anything like that before.
Do a literature search for the structure, perhaps with shorter alkyl chains, methyl or ethyl, and vary the N-protection. You may just find something.
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Offline Messi

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Re: Dimer?
« Reply #7 on: October 30, 2012, 01:28:13 PM »
Ok interesting.

Any idea what the mechanism would be to form the dimer?
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Offline discodermolide

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Re: Dimer?
« Reply #8 on: October 30, 2012, 01:31:59 PM »
Nope, radical maybe?
Or via thioenol(ate)
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Offline Messi

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Re: Dimer?
« Reply #9 on: October 30, 2012, 04:25:22 PM »
Quote from: discodermolide on October 30, 2012, 01:31:59 PM
Nope, radical maybe?
Or via thioenol(ate)

Yes, via thioenol, that's what I thought.

But I was unsure how I could write a mechanism based on the thioenols reacting with each other!
« Last Edit: October 30, 2012, 04:48:53 PM by Messi »
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Offline orgopete

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Re: Dimer?
« Reply #10 on: October 31, 2012, 06:09:48 PM »
Really, you formed a carbon-carbon bond? How did you do that? I could understand an S-S bond, RN=CR'S-SR'C=NR.
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Offline Messi

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Re: Dimer?
« Reply #11 on: October 31, 2012, 06:32:56 PM »
Quote from: orgopete on October 31, 2012, 06:09:48 PM
Really, you formed a carbon-carbon bond? How did you do that? I could understand an S-S bond, RN=CR'S-SR'C=NR.

Yup, well I tried synthesizing the thioamid but NMR showed that the dimer had actually formed. It was one of my products when I purified my product via a column.
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Offline curiouscat

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Re: Dimer?
« Reply #12 on: November 01, 2012, 02:32:47 AM »
Quote from: Messi on October 31, 2012, 06:32:56 PM

Yup, well I tried synthesizing the thioamid but NMR showed that the dimer had actually formed. It was one of my products when I purified my product via a column.

Have you tried repeating the synthesis?
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Offline Messi

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Re: Dimer?
« Reply #13 on: November 01, 2012, 06:49:08 AM »
Quote from: curiouscat on November 01, 2012, 02:32:47 AM
Quote from: Messi on October 31, 2012, 06:32:56 PM

Yup, well I tried synthesizing the thioamid but NMR showed that the dimer had actually formed. It was one of my products when I purified my product via a column.

Have you tried repeating the synthesis?

In the midst of doing so ;)
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Offline curiouscat

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Re: Dimer?
« Reply #14 on: November 01, 2012, 08:09:29 AM »
Quote from: Messi on November 01, 2012, 06:49:08 AM

Have you tried repeating the synthesis?


In the midst of doing so ;)

Great! :) I'm just making sure you are on solid ground.  ;D

Another bizarre defensive idea: Have you double-checked the purity of all your reagents? Is there anything in there that ought not to be in there?  :P

PS. What was your yield?
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