Identifying monomers?

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User947387
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#1
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#1
I am stuck on question 25.

I thought that polymers were simply monomers repeated; i.e. single units repeated and replicated in a chain.

With that in mind, I attempted to break down the monomers, and failed; miserably.

I tried to take each of the given answers then try and work them out; i.e. apply them to the question counting the hydrogens and carbons but that didnt work either for me.

Can anyone give me a general idea as to how to identify monomers; is there some technique?
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charco
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#2
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#2
(Original post by apronedsamurai)
I am stuck on question 25.

I thought that polymers were simply monomers repeated; i.e. single units repeated and replicated in a chain.

With that in mind, I attempted to break down the monomers, and failed; miserably.

I tried to take each of the given answers then try and work them out; i.e. apply them to the question counting the hydrogens and carbons but that didnt work either for me.

Can anyone give me a general idea as to how to identify monomers; is there some technique?
The issue here is that there are two monomers (co-polymers).

Inspection of the side chains shows that there are three consecutive methyl groups at one point. This says that there MUST be a but-2-ene involved.

.. take it from there...
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User947387
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#3
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#3
I have drawn out the formulas in full, operating on your assertion of but-2-ene being involved. However, the remaining four; I keep identifiyng as being 2,3 dimethylbutane :s

Obviously thats wrong....but I don't how/why I am getting it wrong
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charco
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#4
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#4
(Original post by apronedsamurai)
I have drawn out the formulas in full, operating on your assertion of but-2-ene being involved. However, the remaining four; I keep identifiyng as being 2,3 dimethylbutane :s

Obviously thats wrong....but I don't how/why I am getting it wrong
both co-polymers must be alkenes!

There are no sets of three carbons in the chain without branches ... that eliminates ethene...
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User947387
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#5
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#5
Im so sorry.

I still dont understand. Earlier, you stated that there was three consecutive methyl groups, that means that there must be but-2-ene.

However; my understanding was that but-2-ene had C4 H8

I have drawn out the full structural formula of the monomer from the left hand side; including the branches of the methyls. I understand now that it is butene because of the presence of 4 carbons (even including the branches) but when I go to name the compound, as drawn from the information from the question I get 1,2,3 Trimethyl butane....

I KNOW that it "must" be an alkene (therefore butene) because the question does not include alkanes, but where is this descrpancy coming from?

Edit: Polymers; whether condensation polymers or polyamides MUST contain two functional groups. Is that why alkanes are excluded entirely; the alkenes are unsaturated and by virtue of their double bond, are capable of being polymerised?
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awkwardshortguy
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#6
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#6
I may be wrong but if it was but-1-ene you'd have ethyl groups which you don't
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sytner9
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#7
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#7
But-2-ene an propene. Just take two carbon chuncks and you'll see that there's two different repeating units. (The two carbons in the two carbon chunks are in the backbone of the polymer by the way) This makes it easier.
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awkwardshortguy
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#8
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#8
(Original post by apronedsamurai)
I have drawn out the full structural formula of the monomer from the left hand side; including the branches of the methyls. I understand now that it is butene because of the presence of 4 carbons (even including the branches) but when I go to name the compound, as drawn from the information from the question I get 1,2,3 Trimethyl butane....
I could be misunderstanding things completely but just in case this is what you're thinking 1,2,3-trimethylbutane is the repeat unit, made of two monomers
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RachelLJ
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#9
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#9
What's the answer in the marking scheme? And is this SQA?


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Hopefulmedic15
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#10
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#10
(Original post by sytner9)
But-2-ene an propene. Just take two carbon chuncks and you'll see that there's two different repeating units. (The two carbons in the two carbon chunks are in the backbone of the polymer by the way) This makes it easier.
They're right, it's but-2-ene and propene.


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User947387
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#11
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#11
Yes it is SQA (its from a past paper) and the answer is specified as but-1-ene and propene
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RachelLJ
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#12
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#12
Hmmmm I'm doing higher this year and I can't get anything but but-2-ene and propene. The answers might be wrong, but I think it's probably just best if you ask your teacher when you're next at school.


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User947387
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#13
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#13
Sorry! I meant but-2-ene. Was looking at different question
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RachelLJ
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#14
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#14
It's okay. You just have to try and see how the H atoms at the end of the monomers have been cut off. But I think you should probably just ask your teacher because it's hard to explain on TSR


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User947387
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#15
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#15
especially explaining it to a moron like me Thanks guys for not talking down to me
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