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    (Original post by 2013leaver)
    quick question, Why is CDCl3 used in NMR?
    It's a solvent - it carries the molecule in. The Deuterium is used so that a peak/signal is not produced for the CDCl3 on the spectrum.
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    help...I really don't understand the mark scheme for Q4ai and 4aii on the January 2011 paper??
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    Anyone know how to go about the Mass spec questions

    I know what procedure you need to undertake- but don't know how you can just work out exactly what fragment is responsible for what peak?
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    Hello
    I am really struggling with hydrogen NMR, like i can get what all the peaks are and what they are next to but the only help i can find on the internet has the ratio's on. What i dont get is how do you know how many hydrogens are in the environment when you have no ratios?
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    (Original post by rosie66)
    Hello
    I am really struggling with hydrogen NMR, like i can get what all the peaks are and what they are next to but the only help i can find on the internet has the ratio's on. What i dont get is how do you know how many hydrogens are in the environment when you have no ratios?
    (Original post by Tomatochuckers)
    Anyone know how to go about the Mass spec questions

    I know what procedure you need to undertake- but don't know how you can just work out exactly what fragment is responsible for what peak?
    Posted this a few pages back, really helpful in explaining NMR:

    Spoiler:
    Show


    (Original post by kimsiclez)
    This guy explains it really well:

    http://www.youtube.com/watch?v=k6F__pysc74

    But if you're just having trouble putting it all together maybe it's just a case of practising trial and error? Or it could be something in your technique of tackling the question which may make it difficult for you to determine a structure. After watching this guy teach it (and there's another video about combined techniques) I love doing those 10 markers, was so gutted that they didn't come up in jan!

    EDIT: I've added some worksheets that have lots of proton and carbon NMR questions for anyone who wants to practice.
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    (Original post by kimsiclez)
    Posted this a few pages back, really helpful in explaining NMR:

    Spoiler:
    Show




    thank you! this guy is really good; better than my teachers
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    Hi, can anyone explain why, when using an alkane stationary phase, an alkane will have a longer retention time than an alcohol? It's in the Jan 2012 paper (question 4b) and I can't really work out why it's the case (and the markscheme doesn't really explain it either )

    Thanks!
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    (Original post by Jamie66)
    Hi, can anyone explain why, when using an alkane stationary phase, an alkane will have a longer retention time than an alcohol? It's in the Jan 2012 paper (question 4b) and I can't really work out why it's the case (and the markscheme doesn't really explain it either )

    Thanks!
    oooh I did that paper too! isn't it something to do with the hydrogen bonding that the alcohols can do? this probably isn't very helpful...
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    (Original post by Jamie66)
    Hi, can anyone explain why, when using an alkane stationary phase, an alkane will have a longer retention time than an alcohol? It's in the Jan 2012 paper (question 4b) and I can't really work out why it's the case (and the markscheme doesn't really explain it either )

    Thanks!
    I think it's because an alkane is a non-polar molecule while an alcohol is polar? But that's confusing cause I would've thought the polar molecule would be more soluble therefore have a longer retention time? lol sorry I don't really know Dx

    Or maybe cause non-polar alkane with non-polar alkane would dissolve more onto the stationary phase?
    Sorry if I just confused you >_<
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    (Original post by Jamie66)
    Hi, can anyone explain why, when using an alkane stationary phase, an alkane will have a longer retention time than an alcohol? It's in the Jan 2012 paper (question 4b) and I can't really work out why it's the case (and the markscheme doesn't really explain it either )

    Thanks!
    Ask it on the chemistry study help forum. I was going to make a thread later today asking about this but you might aswell create it now.
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    This is my first time doing F324 and hitting around 39-44 marks on every exam paper.
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    (Original post by Jamie66)
    Hi, can anyone explain why, when using an alkane stationary phase, an alkane will have a longer retention time than an alcohol? It's in the Jan 2012 paper (question 4b) and I can't really work out why it's the case (and the markscheme doesn't really explain it either )

    Thanks!
    Like dissolves like.

    So since the alkane is non-polar, another non-polar substance will be more soluble in it. The alcohol is polar so it is not as soluble in the stationary phase, the mobile phase carries it through the column much faster, hence it has a shorter retention time. The alkane spends more time in the stationary phase so it takes longer for it to travel and exit the column.

    Posted from TSR Mobile
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    Hi everyone, please can someone link me to the jan 2013 paper? Thanks also, does anyone know an easy way of predicting the number of Carbon NMR peaks of a compound? I always seem to get half the amount of peaks there is and can't understand why! Thank you
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    Has anyone got the January 2013 F324 paper PLEASEEEE!!!!?

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    (Original post by Raj Kang)
    The splitting patterns would be going top to bottom. Ch3 has no adjacent protons so singlet. Ch2 has 2 adjacent protons so triplet. Ch2 has 3 adjacent protons so quartet. Ch has 2 adjacent protons so splitting of triplet and finally cooh has no adjacent protons so singlet
    I still can't get my head around NMR. Why exactly is the splitting pattern for the amine group a singlet? Was it filled in for us because it was an exception? I'm also a bit confused about what exactly the book means by the adjacent carbon. Am I right in assuming if a proton is attached directly to a carbon it means the carbon(s) adjacent to that carbon, and if the proton is on an attached functional group, it means the carbon the functional group is attached to?
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    tada
    Attached Images
  1. File Type: pdf F324_MS_Jan13.pdf (268.6 KB, 52 views)
  2. File Type: pdf F324-01Jan13.pdf (229.1 KB, 60 views)
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    How can I get an A grade in this exam? Just by doing past papers or is there a magic trick?
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    (Original post by Sly1)
    How can I get an A grade in this exam? Just by doing past papers or is there a magic trick?
    Well you've got 21 hours remaining. Ideally you should've completed all the past papers.
    I would read over the specification, if there is something you don't know go and learn it quickly.

    Posted from TSR Mobile
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    Anyone want to revise?
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    (Original post by wl1)
    I still can't get my head around NMR. Why exactly is the splitting pattern for the amine group a singlet? Was it filled in for us because it was an exception? I'm also a bit confused about what exactly the book means by the adjacent carbon. Am I right in assuming if a proton is attached directly to a carbon it means the carbon(s) adjacent to that carbon, and if the proton is on an attached functional group, it means the carbon the functional group is attached to?
    For nh2 and oh groups these are singlets because they have no adjacent protons by the n+1 rule. Splitting can only occur on adjacent protons, so the next carbon which has protons attached. If no protons are on adjacent carbons on ether side then that specific type of proton is going to be a singlet
 
 
 
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