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Topic: NBS Bromination of EDOT  (Read 4342 times)

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Offline darkdevil

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NBS Bromination of EDOT
« on: May 22, 2013, 08:44:04 AM »
Hi,

I performed the following reaction and expected the radical bromination to occur at the ethylenedioxy position (see the scheme below)
But then I obtained the brominated product at the thiophene position. WHat shall I do if I want to brominate at the ethylenedioxy positions??


The NMR spectrum are as follow,
The blue one is my starting material EDOT, and the red one is the product. It is clear that the aromatic thiophene protons are absent in the NMR spectrum


Upon vacuum solvent removal, the powder which is intially white turned to an insoluble dark blue substance. I guess it polymerized to the insoluble PEDOT (which is blue and insoluble mentioned in literatures). And this further confrmed I obtaned the brominated product at thiophene positions rather than at the ethylenedioxy positions

Offline opsomath

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Re: NBS Bromination of EDOT
« Reply #1 on: May 22, 2013, 09:45:49 AM »
Hi, I've worked with EDOT extensively. It is super electron rich (as you can guess) and polymerizes to PEDOT at the drop of a hat. Also, as you have learned, even the brominated form can polymerize.

In general, when people want to make an EDOT or PDOT derivative substituted on the alkyl part, they make or buy a compound like this: http://www.sigmaaldrich.com/catalog/product/aldrich/687553?lang=en&region=US

If you make it yourself, you generally go through the thiodiglycolic acid route.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA425003


Offline darkdevil

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Re: NBS Bromination of EDOT
« Reply #2 on: May 22, 2013, 10:26:25 AM »
Hi, I've worked with EDOT extensively. It is super electron rich (as you can guess) and polymerizes to PEDOT at the drop of a hat. Also, as you have learned, even the brominated form can polymerize.

In general, when people want to make an EDOT or PDOT derivative substituted on the alkyl part, they make or buy a compound like this: http://www.sigmaaldrich.com/catalog/product/aldrich/687553?lang=en&region=US

If you make it yourself, you generally go through the thiodiglycolic acid route.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA425003

Thank you so much for your reply.
I am working on a single layer oled material. Trying to couple PEDOT with some emissive materials, probably polymeric in nature. But it seems PEDOT is very insoluble in common solvents, and am now trying to make it soluble first.
One more question, if I have a derivatized soluble PEDOT , is it still necessary to dope it (like using PSS polystyrenesulfonic acid) in order to make it conducting? or the doping procedure is just used to further enhance solubility (for insoulube PEDOT) and conductivity?

Offline opsomath

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Re: NBS Bromination of EDOT
« Reply #3 on: May 22, 2013, 10:40:00 AM »
Your question is actually a complicated one, since practically all pure EDOT-based polymers are going to naturally dope in air to some extent (doping is essentially oxidation in p-type materials). But the short version is that while you can experiment with additional doping, I'd expect that an EDOT-based polymer will be a low-band-gap semiconductor in thin film form without any further modification.

Here is another good synthesis for modifying an EDOT monomer, which is simpler than thiodiglycolic acid.

http://pubs.acs.org/doi/pdf/10.1021/ol050573m

Offline darkdevil

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Re: NBS Bromination of EDOT
« Reply #4 on: May 23, 2013, 08:06:49 AM »
Your question is actually a complicated one, since practically all pure EDOT-based polymers are going to naturally dope in air to some extent (doping is essentially oxidation in p-type materials). But the short version is that while you can experiment with additional doping, I'd expect that an EDOT-based polymer will be a low-band-gap semiconductor in thin film form without any further modification.

Here is another good synthesis for modifying an EDOT monomer, which is simpler than thiodiglycolic acid.

http://pubs.acs.org/doi/pdf/10.1021/ol050573m

Thank you for the information.
but.. it is quite expensive to buy Hydroxymethyl EDOT (costs over $100/500MG) in our case.
I also wonder if, going to back to my reaction, I change NBS to 3 equivalents, Will the ethylenedioxy proton be radically substituted to a bromine atom?

Offline opsomath

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Re: NBS Bromination of EDOT
« Reply #5 on: May 23, 2013, 10:47:44 AM »
Unlikely, and then the resulting brominated compound would likely degrade. Do you have an organic chemist supervising your experiments? I wouldn't recommend trying to convert an EDOT CH2 carbon to anything.


Offline darkdevil

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Re: NBS Bromination of EDOT
« Reply #6 on: May 24, 2013, 07:17:58 AM »
Unlikely, and then the resulting brominated compound would likely degrade. Do you have an organic chemist supervising your experiments? I wouldn't recommend trying to convert an EDOT CH2 carbon to anything.

THank you, my supervisor is actually a chemcal engineer

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