Which Materials Are Conjugated Polymers?

[Agalev]

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?

 

[Borek]

How are they defined?

 

[Agalev]

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

 

[Borek]

Sole presence of pi bonds is not enough.

But let's start from here. What is a pi bond? Where is it present?

 

[Agalev]

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

 

[Borek]

There are no alternating single and double bonds in the second molecule!

 

[Agalev]

they have to be round molecules? So 3,4 and the last one are the conjugated polymers

 

[Borek]

Nope. What does "alternate" mean? Compare

-=-=-=-=-=-

and

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

Which one would you call "alternate"?

 

[Agalev]

Yes the first one is alternating. But how does the alternation work when the molecule is round? Is it like the last molecule?

 

[Borek]

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.

 

[Agalev]

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?

 

[Borek]

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).

 

[Agalev]

Thanks a lot, you helpt me a great deal