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    (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
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    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
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    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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    (Original post by KB_97)
    For the PLA question I wrote about how it can be hydrolysed in the body and then hydrogen bond with water molecules because of the polar cooh and oh group on lactic acid. I completely forgot about it being photodegradable too. Oh god..
    Last I checked there's not a lot of light inside your body...
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    Can one of the Admins create a voting radio buttons things so we can all vote on what the A grade boundary will be please??
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    For the percentage yield question I got something like 7.26 g

    Omds I feel like I'm the only one who failed this paper

    It was easy but I made so many silly mistakes I'm so upset now
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    (Original post by Yazmin123)
    why?
    I got nh3+ too. It's acid hydrolysis.
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    I didn't put photodegradable. I thought about it but photodegradation didn't seem to mesh with the dissolving.

    I said that the ester linkages were hydrolysed and the lactic acid dissolved in water due to OH and COOH groups.
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    (Original post by KB_97)
    Attachment 549879

    I got this for the last question. Compound J I think. Anybody else get this?
    YES!
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    2 points at the chromatogram: I write 2 of 3 amino acids have same functional groups, similar adsorption ability, similar distance travel, they will overlap. stitches: I have only written that PLA can undergo hydrolysis to form lactic acid. PLA is solid in rtp because of its long branch and lactic acid is a liquid. NMR of amine: splitting is doublet, quartet of triplets, doublet. Gonna be all wrong I guess......
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    (Original post by Sahil_)
    Was there 3 chiral carbons for tripeptide, 2 on the middle carbon of the amino acids apart from glycine and 1 on the R group for the aminoacid with the long r group?
    yes, there were 3 chiral carbons for the tripeptide
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    (Original post by KB_97)
    Attachment 549879

    I got this for the last question. Compound J I think. Anybody else get this?
    Yeah thats what i got too, have 9 in the proton environment of a singlet so had to be this.
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    (Original post by Yazmin123)
    why?
    As they specifically specified HCL, you had to write NH3 Cl or NH3+ Cl-...

    I knew a lot of people would miss that out.
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    (Original post by izaa29)
    For the percentage yield question I got something like 7.26 g

    Omds I feel like I'm the only one who failed this paper

    It was easy but I made so many silly mistakes I'm so upset now


    I got that aswell
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    Wait you guys... was there a benzene question comparing reactivities? There's one every year but i don't remember there being one this year? UM
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    well there we go then - seems like a name check on hydrogen bonding is needed for 3/3, 1 down already for me lol
    gotdamn H bonds :'((
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    (Original post by GillyTheGhillie)
    Last I checked there's not a lot of light inside your body...
    Not but it was for stitches. And your skin is exposed to uv from sunlight so...idk. I didn't put it down so I hope the answer isn't that it's photodegradable.
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    (Original post by KB_97)
    I got nh3+ too. It's acid hydrolysis.
    yeah exactly!
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    Was compound J (CH3)3C=oCH3
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    Grade Boundary predictions?
 
 
 
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