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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD

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Was photodegradable correct??
Original post by maisym00
Oh god, I wrote about them being photobiodegradavle on exposure to UV😕 Oops


I did the exact same thing lol...
I thought about going for the photodegradable angle, BUT I decided against it bc when polymers photodegrade they break down into waxy residue and then turn into H2O and CO2 and that isn't really dissolving is it? Also I think photodegrading takes a while, longer than hydrolysis + dissolving would anyway
Maybe I'm wrong tho
For the last question, if you get F wrong, you get G and I wrong too right? Meaning forgetting the methyl group and hence putting down a straight chain since G had 4 carbon environments so F would have had to had the methyl group? In this case, would you get 3/4 marks as you got F wrong, but G and I would be ecf? or would you just get 1/4 because you got F wrong hence G and I too?
Original post by RayMasterio
the only hard thing in that exam for me was the NMR table and the tripeptide.


I did the right splitting patterns, but wrong chemical shits :frown:


You better stay on your toilet, then.
Original post by Nightwing2241
Was photodegradable correct??


can't be photodegradable if in body
Reply 1746
Avatar for og556
og556
On the last big question where you had to identify F,G etc, I specifically named them as : 3-methylbutan-2-ol, 3- methyl-butan-2-one, propanoic acid and 3-methylbutylpropanoate. And then I also drew out the structures as they asked.Would this lose me any marks as I think I’ve named them all fine, and gave the reasoning for H with the mr of 74. So do you just get marks for the structures, and do I not need to worry about the naming. Or do they want us to state ’secondary alcohol’ etc. Will my answers be right even though i haven’t explicitly stated what they are in generic terms?
Original post by k.russell
I thought about going for the photodegradable angle, BUT I decided against it bc when polymers photodegrade they break down into waxy residue and then turn into H2O and CO2 and that isn't really dissolving is it? Also I think photodegrading takes a while, longer than hydrolysis + dissolving would anyway
Maybe I'm wrong tho


i said hydrolysed into h20 and c20 too, because of acid in the body though.
so what was answer thats worth 3 marks??
crap i put biodegradable instead of photodegradable

that last question though!!! never fought so hard for 1 mark
Original post by marioman
I talked about it being photodegradable. The thing that made me think that was the "technical terms spelt correctly". Photodegradable has been a 'spelling' mark on a previous paper.


I think the QWC mark would have been for spelling hydrolysis
Original post by Nightwing2241
so what was answer thats worth 3 marks??


No-one knows the exact marking points.
image.jpeg

I got this for the last question. Compound J I think. Anybody else get this?
Original post by Yazmin123
amide hydrolysis question with HCL did you get nh3+ for the amine that had the alcohol attached to it as well?


Incorrect
Hmmm, I'm thinking that was a great test.

In fact it was so easy that I think there are going to be really high grade boundaries this year.
Original post by k.russell
So for the polylactic acid question, I was just wondering what other people put my answer was structured like this;
Polylactic acid is a condensation polymer (polyester)
The ester bond hydrolyses --> c.acid + alcohol
The monomer unit (lactic acid) is soluble in water so the stitches dissolve
Anyone have similar/different points?


Should have wrote it forms hydrogen bonds with water which is why it dissolves
Original post by mil88
Incorrect


why?
Original post by k.russell
I thought about going for the photodegradable angle, BUT I decided against it bc when polymers photodegrade they break down into waxy residue and then turn into H2O and CO2 and that isn't really dissolving is it? Also I think photodegrading takes a while, longer than hydrolysis + dissolving would anyway
Maybe I'm wrong tho


Plus dissolvable stitches are used inside the body, as well as on the surface, where there isn't any light
so what was answer thats worth 3 marks??
I think that for three marks you would say;
PLA is a condensation polymer and hydrolyses in the presence of water
Water is added into the ester functional group, splitting it into a c.acid and an alcohol
The monomer unit, lactic acid, can form hydrogen bonds with water and hence dissolves

I think I most likely got 2/3 cos I didn't talk about H bonds just said LA is water soluble
For the fats question, would the answer be that the one with two double bonds have a higher probability of forming transfats?

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