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Conjugated polymers/materials

  • Thread starter Agalev
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  • #1
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Please post this type of questions in HW section using the template. You have to show your attempts at solving the problem to receive help, this is a forum policy.
Hey,

I'm having a problem for some time finding out which of these materials are conjugated polymers and which aren't.

Can somebody please help me?
polymeren1.png

polymeren2.png
 

Answers and Replies

  • #2
Borek
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How are they defined?
 
  • #3
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This is the only thing I got are the pictures and the defenition of conjugated materials. But I don't know which one's have pi-bonds
 
  • #4
Borek
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Sole presence of pi bonds is not enough.

But lets start from here. What is a pi bond? Where is it present?
 
  • #5
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There has to be an alternating single and double bond like in the second molecule. Also in the thirth a double bound can shift to a single
 
  • #6
Borek
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There are no alternating single and double bonds in the second molecule!
 
  • #7
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they have to be round molecules? So 3,4 and the last one are the conjugated polymers
 
  • #8
Borek
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Nope. What does "alternate" mean? Compare

-=-=-=-=-=-

and

---=---=---=---

Which one would you call "alternate"?
 
  • #9
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Yes the first one is alternating. But how does the alternation work when the molecule is round? Is it like the last molecule?
 
  • #10
Borek
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It doesn't have to go all the way around, but in general it is the same, you are looking for a path consisting of alternate double/single bonds.

To make things more complicated some of these "round" systems are aromatic, which makes their properties different, but that's another story.
 
  • #11
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Ok thanks for your help so far! I thought alternating meant that a bound switches from single to double and vicacersa.

So they are all conjugated except for te second one?

Or is something else to be conciderid for the aromatic compounds?
 
  • #12
Borek
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Fro the polymer to be considered conjugate I don't think it is enough that it contains conjugate bonds - I think the conjugate bond system must extend to the whole molecule (which means it must go through the "main linking chain" of the polymer).
 
  • #13
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Thanks a lot, you helpt me a great deal
 

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