OCR F324-June 2013 Chemistry

They're the building blocks for making proteins for the body, these proteins act as enzymes, antibodies and hormones. The proteins can also transport substances like oxygen, vitamins and minerals around the body. You also have structural proteins such as collagen and keratin which are responsible for the formation of bones, teeth, hair and the outer layer of skin. Our body contains 20 different amino acids which can all be assembled into proteins with the bonds between them being peptide bonds. I could go into the 4 different stages/structures but that's more biology than chemistry.

Next question for you now.
Name the different types of polymers, with examples of each and uses for those examples.


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Yes, bingo!

Ok how many marks is this?

They're the building blocks for making proteins for the body, these proteins act as enzymes, antibodies and hormones. The proteins can also transport substances like oxygen, vitamins and minerals around the body. You also have structural proteins such as collagen and keratin which are responsible for the formation of bones, teeth, hair and the outer layer of skin. Our body contains 20 different amino acids which can all be assembled into proteins with the bonds between them being peptide bonds. I could go into the 4 different stages/structures but that's more biology than chemistry.

Next question for you now.
Name the different types of polymers, with examples of each and uses for those examples.


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condensation polymerisation
polyesters , 2 examples are poly(lactic acid) and terylene
poly(lactic acid) comes from monomers of lactic acid and undergoes condensation reaction in which water molcule is removed and is released as a product(2n-1) and uses of this is that lactic acid is a biodegradable plymer used in food and drink cartoons.

terylene is made from ehtane-1,2-diol and benzene-1,4-dicarboxylic acid and uses of this are making carpets and sports clothes. condensation reaction.

polyamides for example kevlar and nylon-6,6
kevlar made from benzene-1,4-dicarboxylic aicd and benzene-1,4-diamine and used in bullet proof vests and crash car helmets
nylon 6,6 made of hexane-1,4-diamine and hexane-1,4- dicarobxylic acid and used in firefighters.

addition polymerisation for example polystyrene is used in plastic bags

Correct! you're very good at the detail part of the answers which is great!


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thanks, are you sure the monomers were correct? for kevlar and nylone 6,6?

You got the Kevlar monomers correct but after rereading your response you have made a little mistake in your nylon 6-6 monomers, they should be 1,6-diaminohexane and hexane 1,4-dicarboxylic acid or dioic acid, which ever way you prefer to use, good try though.


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thanks, I still hope I said enough for the 6 marks?

Describe the process of optical isomerisim and give the name when there is equal amount of rotation (3)

I'd say you'd lose only 1 mark as you got 1 monomer incorrect but the rest of your information was correct, that's quite a nice position to be in at this point of time.

Okay firstly optical isomers are stereoisomers that are non-superimposable mirror images of each other and the process goes like this:
It arises in organic molecules that contain a carbon atom with 4 different side groups attached to it, this is called the chiral carbon. If a molecule has a chiral centre then there will be two optical isomers which are non-superimposable mirror images of each other. These isomers are chemically identical but they are able to rotate polarised light in different directions. And finally if you've got a balanced mix of them then it's called a racemic mixture.

Hope that'll do.


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Yes, nothing else I could add really! Well done !

My turn

Okay, now I've got to find an interesting one for you, how good are you with definitions? What's the definition for a peptide and also which feature in an amino acid affects the isoelectric point of that amino acid, if you can't do that the name the general structure for an amino acid. (3)


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ok

Peptide is a particular bond that is formed between two amino acids and is formed when the two amino acids have under gone condesation reaction between the carboxyl and amine group due to the removal of h2o molecule. This bond links the two amino acids and there could be dipeptide bonds formation , tri peptide or polypeptide (long chains of amino acid). The feature that affects the isoelectric point could be the amine or carboxyl group becuase this is the point in a PH in which the amino acid exists as a zwitterion, this is where the donation of the H+ ion is involved from carboxyl group to amino group so that no overall charges are present. The general structure of amino acid(alpha amino acid) is RCH2(NH2)COOH. Most amino acids have an isoelectric point which is neutral but some could be acidic or more alkaline depending on the nature of the amino acid.

Very nice and I think my teacher told me that it was the number of amine groups that were in the amino acid which changed the isoelectric point but your answer went into greater detail which is good for my part too as I can learn from you.

My turn.


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Really, the amino acid? I thought that the carboxylic acid also affected the isolelectric point? cause it can lose a proton?

why does COOH get insoluble with water as the chain increases(2)

Well as the number of carbon atoms increase, generally above 5 the solubility decreases because there is a longer non-polar hydrocarbon chain in the molecule doesn't react with the water molecules, not sure what else can be said about it.


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you forgot one key essential word:- Hydrogen bonds
-
My turn

Oh yeah, forgot that key part :-/ at least I'll remember next time and okay.

What are the products formed when you react NH2CH(C2H5)CO-NHCH(CH3)COOH with aqueous sodium hydroxide at 100 degrees temp or 373K to be precise. Hope you can see that structure in a different way. (2)


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Ok if I am looking at the correct structure would the product be..,

NH2CH(C2H5)COO-Na+ + H2NCH(CH3)C0O-NA+ ?