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    (Original post by marioman)
    Yes - as it says on the data sheet, the ranges are only typical values. As for identifying the peak, you generally have to work out the peaks that you know first. For example the cluster of splitting at 7.2 ppm is obviously caused by the protons on a benzene ring. The relative area for this peak is 5, so you know that the benzene ring has 5 protons. Now you can look at the singlet. This is in the right range for a C-H attached to a benzene ring, but if this was the environment then the relative peak area of 3 combined with the singlet means that this would be the end of the molecule and the entire structure would just be a CH3 attached to a benzene ring. This doesn't fit the information given in the question (an ester with mr = 164) so you now know to assign this peak to HC-C=O instead.

    Hopefully this explanation is at least some help - although the best way to get good at NMR is to solve past questions!
    Thanks for the help and for the other person who replied! Yep looking back at it now ive realised that the ring cant have more than one group attatched to it due to the 5 hydrogens on it. Its just under exam conditions with time running out things like that put me off, although i will take your advice and start with the peaks im sure of first to figure out the ones i dont know
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    Why does proton exchange only happen with N-H and O-H groups? Sorry if this is really simple and I'm missing the point
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    (Original post by Vannzzoo)
    Will they mark an annotated mass spec?????
    For the majority of analysis questions, you will receive marks simply by writing down what sections of the Graph mean. For example:
    Mass spec - Molecular ion peaks and fragment ions.
    I.R. Spec - Location, Shape of peak and which functional group it refers to.
    H-NMR - Location, relative size and no. peaks of the split pattern followed by functional group, no. H-atoms involved and no. adjacent H-Atoms.
    C13-NMR - Number of peaks and therefore number of Carbon Environments.
    HOWEVER This must all be written in the answer section of the question. If you write all of this, but leave it as an annotation of the graph, you will most likely receive no marks for what you've written.
    Annotation is useful, but be sure to record it where the paper gives you space to.
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    There hasn't been a question on evaluating Kekule structure in a long time
    I think it could come up
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    What does adding a few drops of D2O do to a proton NMR spectrum?
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    (Original post by KB_97)
    If the alpha amino acid has an r group that has cooh or nh2 and you're asked to draw the zwitterion, do you have to also write them as coo- / nh3+ ?
    if it is just the zwitterion at the normal isoelectric point then you don't protonate or remove the H from the R groups but if there is added acid or alkalie then you do that to the R groups as well as the groups on the alpha amino acid
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    (Original post by ranz)
    worst part is that the exam in afternoon, i just want it over and done with


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    i hate afternoon exams
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    (Original post by itsConnor_)
    Anyone got good question(s) on triglycerides/fatty acids etc.?
    X is a triglyceride. This consists of three fatty acids connected to a single backbone.

    1. Give both the common name and systematic name of the backbone.

    2. Comment of the reaction of the backbone with a standard labatory reagent, represented as [O]. [O] is in excess and this reaction occurs in an environment where it can reach its full extent.

    Include the name of the reagent along with any observations.

    3. Write an equation using [O] to represent the reagent.

    4. Suggest why the organic compound in 3 cannot be hydrolysed.
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    (Original post by xMillnsy)
    What does adding a few drops of D2O do to a proton NMR spectrum?
    removes N-H and O-H peaks from the spectrum so you can identify which peaks were due to these H environments.

    Usually O-H and N-H peaks can span a large range of values (so you can't tell which peak they're causing) so it is easier to just run a spectra with and then without D2O. With D2O the D swaps for the H (forming N-D or O-D) and the peaks for these environments disappear
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    Respek to everyone doing this exam.

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    (Original post by xMillnsy)
    What does adding a few drops of D2O do to a proton NMR spectrum?
    after you add D2O then run the spectra again
    the D replaces H in O-H, N-H and S-H as their protons are labile
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    (Original post by itsConnor_)
    Anyone got good question(s) on triglycerides/fatty acids etc.?
    difference between simple and complex triglyceride
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    (Original post by yoda123)
    There hasn't been a question on evaluating Kekule structure in a long time
    I think it could come up
    does last year's q 2a count as one?
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    (Original post by tcameron)
    if it is just the zwitterion at the normal isoelectric point then you don't protonate or remove the H from the R groups but if there is added acid or alkalie then you do that to the R groups as well as the groups on the alpha amino acid
    but whqt if there are equal amount if carboxylic acids and amines?


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    Can someone explain how on earth the answer to this is 1.35g not 0.216g...?!Name:  image.jpg
Views: 178
Size:  498.9 KB
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    (Original post by ranz)
    but whqt if there are equal amount if carboxylic acids and amines?


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    The same still applies
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    (Original post by Mathematicus65)
    Can someone explain how on earth the answer to this is 1.35g not 0.216g...?!Name:  image.jpg
Views: 178
Size:  498.9 KB
    0.05 mol on top its actual / theoretical yield


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    (Original post by Mathematicus65)
    Can someone explain how on earth the answer to this is 1.35g not 0.216g...?!<snip>
    You have got the scaling the wrong way round. 1.73 g is 40% of the theoretical yield.
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    (Original post by tcameron)
    The same still applies
    oh, r u suree?


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    (Original post by Rust Cohle)
    X is a triglyceride. This consists of three fatty acids connected to a single backbone.

    1. Give both the common name and systematic name of the backbone.

    2. Comment of the reaction of the backbone with a standard labatory reagent, represented as [O]. [O] is in excess and this reaction occurs in an environment where it can reach its full extent.

    Include the name of the reagent along with any observations.

    3. Write an equation using [O] to represent the reagent.

    4. Suggest why the pH of the organic compound in 3 cannot be hydrolysed.
    1. Glycerol and propane-1,2,3-triol (came up in june 13 tho )
    2. Colour change from orange to green (oxidation using acidified K2Cr2O7, H2SO4 catalyst), heat under reflux
    3. CH2OHCH(OH)CH2OH + 5[O] --> COOHCOCOOH + 3H2O
    4. ?

    EDIT: for 4 is it cos no ester linkage or amide linkage?
 
 
 
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