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

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    Stearic acid is the most likely to cause CHD as saturated fats cause LDLs to build up and hence bad cholesterol.

    (drawing a triglycerides formed of a glycerol and three fatty acid chains + a trans fat)

    Cis-trans isomerism requires different groups attached to each carbon in c=c bond.

    Alcohol and amide functional groups

    Condensation polymer was polyamide + used in clothing

    Mention levels of adsorption leading to separation. Then measure Rf values and compare with known Rf values. 2 spots instead of 3 because compounds may not have separated fully and hence have similar Rf values etc..

    Polylactic acid could breakdown because ester linkages can be hydrolysed (acid/alkali) and the C=O bond is photodegradable as absorbs IR radiation.

    Percentage yield mass = 2.66g (2.6564)

    2 optical isomers are made when molecule is synthesised unnaturally compared to only 1 when synthesised naturally

    Formula for peak A was just molecular formula with positive charge
    Peak B was CH3CH2NH2 + positive charge with m/z of 44

    Rest of question on identifying the compounds

    Please add to it will help everyone out xx not all will be right
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    (Original post by cr7alwayz)
    For the first step of the incomplete mechanism question (2 marks),

    I just put positive dipole on the carbon and negative dipole on the oxygen.
    And a curly arrow going from the double bond to the oxygen.

    Did we have to draw the OH- attacking the carbon with a curly arrow as well?
    yeah i thought it was like a reduction except we use OH-
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    (Original post by Spwoosh)
    It wouldn't be branched at all, everybody just got a little over excited and over complicated it. It's literally ch3ch2ch2ch(oh)ch3. CNMR peaks are the distance of the carbons from the electronegative point. The Ch2 next to the Ch(oh) will have the same peak as the Ch3 on the other end of the Ch(oh) so there are only 4 peaks. We were right. The answer most people got was wrong because if you look at it carefully you'd see it only has 3 peaks.
    The correct answer was CH3CHOHCH(CH3)2. There was branching. fight me.
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    (Original post by popo111)
    Can someone confirm, is the first answer saturated fat or the other unsaturated ones??
    It is definitely saturated. The question said NATURALLY occurring fatty acids and the majority of naturally occurring ones are Cis, only becoming Trans when undergoing Dehydrogenation. Plus, there was no way to tell whether Oleic or Linoleum acid were Cis or Trans but Saturated fats definitely increase your L Cholesterol levels.
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    (Original post by faglad202)
    I wrote the one with 2 double bonds purely becuase it leads to more trans structures?
    Surely if the structure had one trans configuration and the other was cis then it wouldn't pack closely together?? so out of four combinations(cis,cis)(cis,trans) (trans,cis)(trans,trans) only one (trans,trans) would be really bad? Im not really sure though i kept self doubting loads with that question.
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    (Original post by cr7alwayz)
    For the first step of the incomplete mechanism question (2 marks),

    I just put positive dipole on the carbon and negative dipole on the oxygen.
    And a curly arrow going from the double bond to the oxygen.

    Did we have to draw the OH- attacking the carbon with a curly arrow as well?
    yes, cus OH is in the product
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    (Original post by popo111)
    Exactly!

    NMR is like my specialty man, I got 6/7 on last years question because I didn't comment on the N-H peak!
    Im kinda fed up that all my hard work at gone to nothing and can't quite get my head around how people found this year easy and 2015 hard

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    (Original post by popo111)
    Can someone confirm, is the first answer saturated fat or the other unsaturated ones??
    Saturated is bad for you 95% sure


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    What do people think the boundaries will be for a grade C?
    Also can anyone explain how they worked out the percentage yield question?
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    Did anyone find this exam hard?

    I thought it was a nice paper but made a few silly mistakes :/
    What did everyone get for the splitting patterns of the compound after D20 had been added?I got two doublets and one singlet.
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    (Original post by anndz3007)
    yeah you not include it but it still affect the chemical shift no ??
    I doubt it.
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    (Original post by Ula456)
    Did anyone find this exam hard?

    I thought it was a nice paper but made a few silly mistakes :/
    What did everyone get for the splitting patterns of the compound after D20 had been added?I got two doublets and one singlet.
    2 doublets and a sextuplet iirc


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    (Original post by JennyMoorcroft)
    My friend wrote his structures in pencil, will the pencil pick up for marking?
    Yes i got a copy of my f322 back and i had drawn in pencil and you could see it on the scanned image, i also did all mine in pencil so i really hope so
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    what might the grade boundaries be?
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    using exact numbers isn't the % yield 2.67 not 2.66!!!???! To 3sf
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    (Original post by cr7alwayz)
    For the first step of the incomplete mechanism question (2 marks),

    I just put positive dipole on the carbon and negative dipole on the oxygen.
    And a curly arrow going from the double bond to the oxygen.

    Did we have to draw the OH- attacking the carbon with a curly arrow as well?
    You had to:

    -draw a positive dipole on the carbon in the carbonyl group, negative dipole on the attatched oxygen
    -a curly arrow going from either the negative charge OR the lone pair on the OH- ion to the carbon
    -and lastly you needed to draw an arrow from the C=O bond to the oxygen
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    (Original post by Hunnybeebee)
    Im kinda fed up that all my hard work at gone to nothing and can't quite get my head around how people found this year easy and 2015 hard

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    Just our luck eh!

    Nah real talk, just looking at these posts, many ppl made mistakes, so we'll have to see...

    Hopefully, F325 will benefit us!
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    (Original post by Spwoosh)
    It wouldn't be branched at all, everybody just got a little over excited and over complicated it. It's literally ch3ch2ch2ch(oh)ch3. CNMR peaks are the distance of the carbons from the electronegative point. The Ch2 next to the Ch(oh) will have the same peak as the Ch3 on the other end of the Ch(oh) so there are only 4 peaks. We were right. The answer most people got was wrong because if you look at it carefully you'd see it only has 3 peaks.
    nah it has to be branched for the 13C nmr to only have 4 environments, in ch3coch2(ch3)2 the last 2 methyls have the same environment
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    (Original post by Ula456)
    Did anyone find this exam hard?

    I thought it was a nice paper but made a few silly mistakes :/
    What did everyone get for the splitting patterns of the compound after D20 had been added?I got two doublets and one singlet.
    It was two doublets and one Sextet (a multiplet would have sufficed)
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    (Original post by GawdHeresEmmie)
    The invigilators always say 'pencils may be used for drawings and rough notes' so I should assume so! (i go over mine in pen afterwards though bc I worry)



    I don't think thats right? (CH3)2CHCH(OH)CH3 would give 4, not 3 peaks, as the two methyl groups are in identical environments.
    Yes, the 2 methyl groups would give 1 peak but the CH2 next to the CH(0h) and the CH3 on the other side will both ALSO give only 1 peak since they are both right next to the carbon with the oxygen. That just leaves the CH(oh) by itself which would make the third and final peak. Sat down with about 10 of my mates after this exam to talk it through and we all decided the straight chain was the only possible answer.
 
 
 
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