Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: iamthepolice on February 21, 2007, 09:20:30 AM
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im stuck! i need help. i really dont understand how to answer this question? well firstly i did an experiment about a polymerization of methyl methacrylate.
i'll just quickly show what i carried out:
1. i got polyvinly alcohol dissolved it in water and heated it, its under reflux
2. dissolved benzoyl peroxide in a monomer (methyl methacryalte)
3. added it to the polyvinyl alcohol drop by drop.
4. then once it was heated for some time i took it all out an placed it into a beaker
5. filtered the solution using a buchner funnel and dryed it.
for the result i should have got some yellowy spherical entities.. but i didnt.
now for the questions...grrrr
i dont know how to do the equations for the reaction which occurs in this experiment.
please help
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omg i thought this is a chemistry help forum! :-[
i honestly need help i dont know how to do chemical equations.
at least start me off and point me in the correct direction..
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You have yet to ask a question.
This is a Chemistry Help Forum, but you can't expect us to be here all the time. If you have something due right away, it is your own responsibility to of started it earlier.
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lol its not in till 2 weeks...
i understand that you wont be here all the time, but im just asking for help...
the question is:
show using equations the reactions which occur?
now i really dont know where and how to start....
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Somehow I find it hard to believe that you were not told or pointed to to the necessary information.
What is your monomer?
What is polymerisation? What happens to monomer during polymerisation?
What role benzoyl peroxide plays?
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What is your monomer? = methyl methacrylate
What is polymerisation? = when polymer chains react with each other.. to be honest i dont know
What happens to monomer during polymerisation? = i really dont have a clue
What role benzoyl peroxide plays? the initiator...
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http://en.wikipedia.org/wiki/Polymerisation
Look at your monomer structure and think, how can it polymerise.
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well methyl methacrylate is a CC(=C)C(=O)OC is that how u write it?
how does it polymeralise...erm does it like attach it to benzoyl peroxide (C6H5CO)2O2
but how does it become as one?
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well methyl methacrylate is a CC(=C)C(=O)OC is that how u write it?
SMILES is one of the notations, I am asking about the structure. It should look similar to the strcutures shown in wikipedia article about polymerization. Draw all atoms and all bonds. As long as you have no idea how it looks alike you have no chances of understanding what is going on.
how does it polymeralise...erm does it like attach it to benzoyl peroxide (C6H5CO)2O2
but how does it become as one?
Looks like you have no idea what polymerization is. Look at the first picture in wikipedia article. Do you see what happens to the monomers? Look slightly below at picture signed Fig. 1 - do you see what is hapening? Now try to imagine what will happen to your monomer during polymerization. Don't bother with initiator for now.
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it breaks! the long chains break
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Quite the opposite.
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oky now im confussed, the chains join together but where? i just cant stick it anywhere lol...
so its:
benzoyl peroxide + methyl methacrylate = ??
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I told you - don't bother with initiator for now. Try to find out how your monomer and your polymer look alike, no matter what happens at the chain ends.
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Here is an example, the polymerisation of styrene: http://upload.wikimedia.org/wikipedia/commons/thumb/6/6e/Styren.png/400px-Styren.png
As Borek has said, apply what happens in the polymerisation of styrene to that of methyl acrylate.
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oh i see....so does that mean it will look like this: ive put it on the attachments...hope it shows up
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The bonds it that picture that are drawn like this: ___....___ between the repeating units should be solid bonds. Apart from that, fine.
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ahh thanks....
one more question, when you add benzoyl peroxide and methyl methacrylate what does it make?
can you briefly write the equation for me please..
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Take a look at the benzoyl peroxide structure. What happens is that the oxyngen-oxygen bond easily breaks and free radicals are generated. these free radicals attach themselves to the double bond carbon-carbon in your monomer starting chain reaction. Thus - assuming that initiator has formula A-A and your monomer is M what you will get is A-(M)n-A molecule.
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oky cool,
now i dont know which way to write this all down. because the question is asking: show using equations the reactions which occur?
does that mean i write it down in its structural form or the other way. (i dont know whats it called)
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There are three phases: inititaion, polymerization, ending. First one is two step (peroxide decomposition and attack on the first monomer). You should be able to write all reactions now.
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ohh i see, ive got an idea now:
so like the 1st step is initiation
2nd propagation
3rd termination
are these the three steps?
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Yes. Don't bother with my nomenclature :)
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oky, thanks 4 ya help..
ive got another question....
Q- give 2 reasons why suspension polymerisation is used instead of bulk polymerisation?
ive looked in the book that ive got, but its not in there...
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Think about the heat of reaction and what might happen.
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erm will it get extremely hot?
i was thinking in the lines of it being:
-cheaper
-environmentally friendly
-more active sites available therefore the reagent made more efficiently due to it increasing the rate of reaction....
i duno if thats correct...
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Is reaction kinetic temperature dependent?