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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: hockey101 on April 08, 2013, 07:26:14 PM

Title: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 08, 2013, 07:26:14 PM
Hey everyone...I'm having a really hard time following on how to draw dimers of plastics.

Here is the situation:

My teacher gave us this yellow sheet with a bunch of boxes on them.  One box labels the plastic identification code all the way up to 6 (yes I know there is 7 but it's labeled as an other which means it's pretty much unknown).  Another box labels its complete name, the next box labels as a monomer, the next a dimer, and then the last box labels the type of polymerization required to form the polymer (Addition or Condensation).

So here is what I'm really not understanding:

For example:

Plastic Code: 3
Complete Name: Polyvinyl Chloride (PVC)
Monomer: H    H
              |    |
              C = C
              |    |
              Cl   H

Dimer:  H H H  H
          |  |  |  |
         -C-C-C-C-
          |  |  |  |
          H H  Cl H
Polymerization: Addition

When I'm drawing a dimer, how do I know where to put the chlorine?
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Borek on April 09, 2013, 04:21:52 AM
On every second carbon. But I agree it is not 100% obvious.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 09, 2013, 11:06:07 AM
But its on the 3rd Carbon in this example....
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 09, 2013, 06:24:26 PM
So I'm still not understanding...you say that it's always on the 2nd carbon...in this example its on the 3rd.


Here is another example that I don't understand:

Code: 6
Name: Polystyrene
Monomoer: H    H
                |    |
                C = C
                |    |
                Θ   H

Dimer:   H  H H H
            |  |  | |
          -C-C-C-C-
            |  |  | |
            Θ H  Θ H

Type of Polymerization: Addition


(The thetas in this example represent the Benzenes since you can't insert a benzene on here)

So for this problem there was only 1 benzene in the monomer, but then in the Dimer the benzenes showed up on the 1st and the 3rd carbon.  I don't understand how this happens.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Big-Daddy on April 09, 2013, 07:42:36 PM
Surely you either produce the dimer (e.g. C(Cl)CC(Cl)C) or the addition polymer itself?

But from the examples you have given, basically:

Monomer: [*:1]C([*:2])=C([*:3])[*:4]

Then the dimer is:

Monomer: [*:1]C([*:2])C([*:3])([*:4])C([*:1])([*:2])C([*:3])([*:4])

Where the bonds which aren't shown, which you would otherwise assume to be C-H, either actually are C-H (if this is a dimer, i.e. 2 combined monomers, you're drawing) or are C-C extending to outside the repeat unit.

Sorry for the slightly unclear diagram, it was the best I could get out of smiles.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 09, 2013, 07:52:05 PM
Ok....so then why on my first example is the chlorine on the 3rd carbon instead of the 1st?
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Big-Daddy on April 09, 2013, 08:27:04 PM
Ok....so then why on my first example is the chlorine on the 3rd carbon instead of the 1st?

If I understand your meaning of "dimer", and you are referring to repeat units of a polymer but for some reason with the repeat unit drawn in twice, then the Cl should be on both the first and third C (as Borek said, every 2nd C, so if you drew a tetramer then the Cl would be on the first, third, fifth and seventh of your 8 C atoms).
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 09, 2013, 08:40:47 PM
I have no idea what you are talking about....
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 09, 2013, 08:45:57 PM
I really don't know how I am supposed to memorize all the identification codes, all the monomers and dimers of the polymers, then let alone draw them.  Most of this is not even in the chem book which really sucks because then I can't look at examples from the book that would give explanations.  I'm also supposed to memorize the natural polymers, discuss the characteristics of polyacrylate, including current and potential uses of this polymer (which I have no clue what that is and I can't find it anywhere that can explain it too me).  I'm also supposed to list all the characterisitcs of thermoset and thermoplastic polymers...like how on earth am I supposed to know all this????
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Borek on April 10, 2013, 04:10:32 AM
You don't have to memorize dimers when you know what the monomer is.

Dimer is produced when two monomers combine, so its formula simply contains twice the monomer. There are some possible complications, but I have a feeling you are missing the basics ATM.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: DrCMS on April 10, 2013, 04:22:36 AM
I really don't know how I am supposed to memorize all the identification codes, all the monomers and dimers of the polymers, then let alone draw them.  Most of this is not even in the chem book which really sucks because then I can't look at examples from the book that would give explanations.  I'm also supposed to memorize the natural polymers, discuss the characteristics of polyacrylate, including current and potential uses of this polymer (which I have no clue what that is and I can't find it anywhere that can explain it too me).  I'm also supposed to list all the characterisitcs of thermoset and thermoplastic polymers...like how on earth am I supposed to know all this????

Stop this whingfest and do so independent reseach google/wikipedia will give you loads of info on this and put some thought into your work; alternatively carry on whinging get nowhere drop out of school and end up in the gutter.

A monomer is the smallest unit that a polymer is made from  (the give away is in the name mono = one while poly = many). 
A dimer is just two monomers joined together (the give away is again in the name di = two).  So if the monomer contains 1 chlorine or phenyl group then the dimer will contain 2 of them.

Polyacrylate is a very wide range of polymers that have many many uses (an acrylate monomer could be acrylic acid, methyl acrylate, ethyl acrylate butyl acrylate etc.). 
Polyacrylic acid as a low molecular weight solution of its sodium salt is used as a dispersant/anti-scale but as a high molecular weight solid it is used as a superabsorbant polymer in nappies etc.

So go do some work our your own and then come back if you have specific questions; we're not here just to do all your howework for you while you learn nothing.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Big-Daddy on April 10, 2013, 06:34:03 AM
I have no idea what you are talking about....

I don't see how it's humanly possible to be clearer than I was.

The Cl is on the first and third C. Do you understand me? It is NOT only on the third C. The diagram is WRONG.

DrCMS, how does the chain end if the molecule is a dimer? Do you have 2 extra C-H bonds coming in to finish the chain (which otherwise is a polymer where n=2 repeat units)?
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: DrCMS on April 10, 2013, 08:37:32 AM
DrCMS, how does the chain end if the molecule is a dimer? Do you have 2 extra C-H bonds coming in to finish the chain (which otherwise is a polymer where n=2 repeat units)?

In reality what is at the ends of a polymer (dimer) chain depends on the conditions used in the polymerisation, it might be an initiator fragment and one end and a C-H via abstraction from the solvent or another polymer chain at the other end.  Or it might be and intiator fragment at one end and from a chain transfer agent, added to control the molecular weight distrubition, at the other end etc etc.  See this for extra info http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/polymers.htm
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 10, 2013, 11:05:01 AM
I have no idea what you are talking about....

I don't see how it's humanly possible to be clearer than I was.

The Cl is on the first and third C. Do you understand me? It is NOT only on the third C. The diagram is WRONG.

DrCMS, how does the chain end if the molecule is a dimer? Do you have 2 extra C-H bonds coming in to finish the chain (which otherwise is a polymer where n=2 repeat units)?

So my teacher was wrong....and didn't have the right diagram....and to answer your question you end the dimer with brackets to show that it's repeating
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 10, 2013, 11:13:08 AM
DrCMS, how does the chain end if the molecule is a dimer? Do you have 2 extra C-H bonds coming in to finish the chain (which otherwise is a polymer where n=2 repeat units)?

In reality what is at the ends of a polymer (dimer) chain depends on the conditions used in the polymerisation, it might be an initiator fragment and one end and a C-H via abstraction from the solvent or another polymer chain at the other end.  Or it might be and intiator fragment at one end and from a chain transfer agent, added to control the molecular weight distrubition, at the other end etc etc.  See this for extra info http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/polymers.htm


I love how when I try to look for a website like that...I can never find one...haha...thanks that helped...A LOT
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Big-Daddy on April 10, 2013, 11:27:37 AM
I have no idea what you are talking about....

I don't see how it's humanly possible to be clearer than I was.

The Cl is on the first and third C. Do you understand me? It is NOT only on the third C. The diagram is WRONG.

DrCMS, how does the chain end if the molecule is a dimer? Do you have 2 extra C-H bonds coming in to finish the chain (which otherwise is a polymer where n=2 repeat units)?

So my teacher was wrong....and didn't have the right diagram....and to answer your question you end the dimer with brackets to show that it's repeating

Yes, if indeed he missed out that Cl. As Borek said, the Cl comes on every second carbon.

What is the use of simply drawing 2 repeat units and then writing that you repeat this n times? Why not just draw one, and then write (n) repeats, like normal with addition polymerization? In my experience, a dimer corresponds to an actual molecule which is a 2-repeat of the original (i.e. a polymer where n=2), and the question when drawing it becomes, what forms the ends of the chain. It's been answered now.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 10, 2013, 05:42:35 PM
I really don't know how I am supposed to memorize all the identification codes, all the monomers and dimers of the polymers, then let alone draw them.  Most of this is not even in the chem book which really sucks because then I can't look at examples from the book that would give explanations.  I'm also supposed to memorize the natural polymers, discuss the characteristics of polyacrylate, including current and potential uses of this polymer (which I have no clue what that is and I can't find it anywhere that can explain it too me).  I'm also supposed to list all the characterisitcs of thermoset and thermoplastic polymers...like how on earth am I supposed to know all this????

Stop this whingfest and do so independent reseach google/wikipedia will give you loads of info on this and put some thought into your work; alternatively carry on whinging get nowhere drop out of school and end up in the gutter.

A monomer is the smallest unit that a polymer is made from  (the give away is in the name mono = one while poly = many). 
A dimer is just two monomers joined together (the give away is again in the name di = two).  So if the monomer contains 1 chlorine or phenyl group then the dimer will contain 2 of them.

Polyacrylate is a very wide range of polymers that have many many uses (an acrylate monomer could be acrylic acid, methyl acrylate, ethyl acrylate butyl acrylate etc.). 
Polyacrylic acid as a low molecular weight solution of its sodium salt is used as a dispersant/anti-scale but as a high molecular weight solid it is used as a superabsorbant polymer in nappies etc.

So go do some work our your own and then come back if you have specific questions; we're not here just to do all your howework for you while you learn nothing.


I never asked for you to answer all those questions...now did I?  That was your decision.  I was just stating what I was struggling with and those questions weren't meant for you or anyone to answer.  I have been studying the same subject for 7 hrs a day for almost a week straight and when you don't understand somethings, that's when you start to ask questions.  All those things I listed were from my objective sheet and I knew most of those things, but when you study some of the other objectives you might forget some of the things you just learned.  I just felt overwhelmed with all the letters and numbers and all the memorization.  And btw this isn't homework...it's studying for a test and fyi...I did a lot of research..and I wasn't understanding some of it so I came here for help.  Also, I am a straight A student, don't be telling me to stop with the whingfest stuff when you don't know what I have done and what I haven't done.

Summary:  Watch what you say before you actually know what the situation is.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Big-Daddy on April 10, 2013, 06:16:46 PM
I really don't know how I am supposed to memorize all the identification codes, all the monomers and dimers of the polymers, then let alone draw them.  Most of this is not even in the chem book which really sucks because then I can't look at examples from the book that would give explanations.  I'm also supposed to memorize the natural polymers, discuss the characteristics of polyacrylate, including current and potential uses of this polymer (which I have no clue what that is and I can't find it anywhere that can explain it too me).  I'm also supposed to list all the characterisitcs of thermoset and thermoplastic polymers...like how on earth am I supposed to know all this????

Stop this whingfest and do so independent reseach google/wikipedia will give you loads of info on this and put some thought into your work; alternatively carry on whinging get nowhere drop out of school and end up in the gutter.

A monomer is the smallest unit that a polymer is made from  (the give away is in the name mono = one while poly = many). 
A dimer is just two monomers joined together (the give away is again in the name di = two).  So if the monomer contains 1 chlorine or phenyl group then the dimer will contain 2 of them.

Polyacrylate is a very wide range of polymers that have many many uses (an acrylate monomer could be acrylic acid, methyl acrylate, ethyl acrylate butyl acrylate etc.). 
Polyacrylic acid as a low molecular weight solution of its sodium salt is used as a dispersant/anti-scale but as a high molecular weight solid it is used as a superabsorbant polymer in nappies etc.

So go do some work our your own and then come back if you have specific questions; we're not here just to do all your howework for you while you learn nothing.


I never asked for you to answer all those questions...now did I?  That was your decision.  I was just stating what I was struggling with and those questions weren't meant for you or anyone to answer.  I have been studying the same subject for 7 hrs a day for almost a week straight and when you don't understand somethings, that's when you start to ask questions.  All those things I listed were from my objective sheet and I knew most of those things, but when you study some of the other objectives you might forget some of the things you just learned.  I just felt overwhelmed with all the letters and numbers and all the memorization.  And btw this isn't homework...it's studying for a test and fyi...I did a lot of research..and I wasn't understanding some of it so I came here for help.  Also, I am a straight A student, don't be telling me to stop with the whingfest stuff when you don't know what I have done and what I haven't done.

Summary:  Watch what you say before you actually know what the situation is.

No the issue isn't what kind of a student you are but why you ask a question on a forum to which the answer is the first thing that comes up from a well-chosen Google search on "addition polymerisation". You should first understand what happens in addition polymerisation before figuring out what happens with "polyacrylate"; this will just be a miniscule subset of the overall picture. I represented this in my R-group diagram earlier.

Although I can understand why you might be confused given that the diagram for the first question appears to be wrong, and given that as far as I know there's no good reason to write 2 absolutely identical repeat units and call this a "dimer" (which it isn't) rather than just writing 1. A dimer should end in some way, as Dr CMS explained to me earlier. It does not have n repeat units. That's a polymer.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 10, 2013, 06:33:04 PM
All I asked was why my diagram looked different from the rest of the others.  I did look it up online but wasn't sure if my teacher was right or the "internet" was right. We all should know that sometimes the internet can be wrong and some people make answers up. The reason I said what kind of student I am is because DrCMS said somethings he probably shouldn't have that I took offensively.  I never asked you guys to do my homework now did I?  No I did not.  Plus, you don't tell someone that they are whinging when you have no idea what they have done.   

And on this sheet that I have with all the Plastics, it had a monomer and a dimer.  It wasn't so much about the polymer itself but more about the monomer and dimer.   
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: DrCMS on April 11, 2013, 05:27:53 AM
All I asked was why my diagram looked different from the rest of the others.

No you did not you said "I do not understand...."  You did not ask specific questions you just moaned.  If you'd asked why in the monomer is there one Cl but in the dimer there is still only one Cl should it not have two Cl's we'd have been able to answer your easily.  So when you ask a question make it clear what you are asking.

I did look it up online but wasn't sure if my teacher was right or the "internet" was right. We all should know that sometimes the internet can be wrong and some people make answers up. 

You did not say any of this in your first few posts at all.

The reason I said what kind of student I am is because DrCMS said somethings he probably shouldn't have that I took offensively.   

I said exactly what I did because you were just complaining about how difficult it was without asking us a question - that is a whingfest.  If you are a straight A student then you should have been able to figure it out yourself or present a more coherent set of questions for us to help your work through.

I never asked you guys to do my homework now did I?  No I did not.

Yes you did that is why you are here.

Plus, you don't tell someone that they are whinging when you have no idea what they have done.

I tell some one to stop whinging when they are WHINGING and you were whinging.
Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: hockey101 on April 11, 2013, 11:12:50 AM
It was not homework....it was a diagram that my teacher had given to us to study for the test today...so i asked a question on how I should know where to put the Cl's and I did ask where the 2 Cl's were and Borek answered my question...I just wasn't comprehending what he was trying to say so I gave him another example of how the 2 examples were different.  After I read his post a few times, I saw what he was saying.  Plus I shouldn't have to say all the things I have done and researched.  If you really want to see what I have done I will post all the websites that I searched over the past week.  (it wouldn't fit into one post).  I'll give you that I shouldn't have posted the "whinging" post but you don't tell someone there going to drop out of school because of "whinging" and go do some independent research when I have done a whole bunch of independent research and you don't say that were not doing all your homework and for you too learn nothing.  I shouldn't have to explain everything I do or say.  But apparently some people like you need a background story of my life and all the things I have done.   

Title: Re: Monomer and Dimer of Polyvinyl Chloride (PVC)
Post by: Borek on April 11, 2013, 11:17:00 AM
Topic locked. Chemistry ended several posts ago.