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    how do you work out the peaks? e.g. for 2,3-dibromopentane?
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    Ignore me I need sleep!
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    (Original post by kohlstream)
    2 lots of R-CH3, and 9 protons in this envmt
    R-CH2-R, 2 protons in this envmt
    I havent got data sheets with me, but theres the H attached to C which is attached to br

    Therefore peaks will be 9:2:1

    Then find out where each peak should go, i.e. R-CH3 at 0.8-1.2

    Sorry the answer is a bit woolly, i have to go revise!
    ar the realtive peaks 3:2:1 ? but the actual peaks 9:2:1?

    saying that.. shouldn't the '9' be a '6', cause you said there were 2 lots of CH3!

    I'm confused!
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    (Original post by roochis)
    ar the realtive peaks 3:2:1 ? but the actual peaks 9:2:1?

    saying that.. shouldn't the '9' be a '6', cause you said there were 2 lots of CH3!

    I'm confused!
    I meant three lots of R-CH3, i'll edit it.

    I have no idea about the peaks
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    2,3 - dibromopentane:

    i would say 4 different environments (4 different peaks) in the ratio 3:2:2:3

    carbons 2 & 3 are probably the same environment (2 protons in total). The difference between them is almost certainly not obvious on an n.m.r that we would get. Then the rest are different - 3 more carbons, 3 more environments. The two CH3's are different because one is next to a bromo group - very influential.
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    How are there 3 lots of CH3?

    There are only 2 no?

    CH3-CHBr-CHBr-CH2-CH3
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    Don't know exactly where each peak is - don't have a data table with me, and can't be bothered anyway - that's the sort of thing I'm not going to worry about cos you only have to read it off in the exam.
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    (Original post by CrazyChemist)
    2,3 - dibromopentane:

    i would say 4 different environments (4 different peaks) in the ratio 3:2:2:3

    carbons 2 & 3 are probably the same environment (2 protons in total). The difference between them is almost certainly not obvious on an n.m.r that we would get. Then the rest are different - 3 more carbons, 3 more environments. The two CH3's are different because one is next to a bromo group - very influential.
    I think thats right... i can never do the environments thing unless i draw it out!
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    (Original post by roochis)
    I think thats right... i can never do the environments thing unless i draw it out!
    Good advice - that's what i did!
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    i thought there were 5 environments, as the carbons next to each one infulence, it so carbon 2 has a methyl next to it, whilst carbon 3 has an ethyl, so it'd be like, 3:1:1:2:3
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    5 different proton environments and 5 different carbon ones. You really need to specify what sort of an NMR you're looking at - eg, 1H NMR, or 13C NMR.

    Ben
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    (Original post by colombiche)
    i thought there were 5 environments, as the carbons next to each one infulence, it so carbon 2 has a methyl next to it, whilst carbon 3 has an ethyl, so it'd be like, 3:1:1:2:3
    There are 5 different environments, but two of them are very similar (the '2' and '3' carbons) and so i think the difference between them would be very slight. I suspect the difference between the '1' and '4' carbon would be big enough to show up obviously, but between the '2' and '3' there is a very slight difference, so it wouldn't be two distinct peaks. Wrong?
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    (Original post by colombiche)
    i thought there were 5 environments, as the carbons next to each one infulence, it so carbon 2 has a methyl next to it, whilst carbon 3 has an ethyl, so it'd be like, 3:1:1:2:3
    Exactly.

    Ben
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    (Original post by Ben.S.)
    5 different proton environments and 5 different carbon ones. You really need to specify what sort of an NMR you're looking at - eg, 1H NMR, or 13C NMR.

    Ben
    We only do 1H NMR.
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    (Original post by CrazyChemist)
    We only do 1H NMR.
    But 'we' don't! Who are you? Nobody has specified what course this is for (although it is pretty obviously the first A2 module). I was just being a bit pedantic!

    Ben
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    Ah...oops. sorry . I'm doing OCR Salters. P'raps i should shut up...

    EDIT: what the hell...I'm saying 3:2:2:3 and leaving you to it I'm off - got chem exam tomorrow on this...goodnight! :goodnight
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    im sayin 5 peaks..of height 3, 1, 1, 2, 3
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    do we need to know high resolution NMR?
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    not for edexcel
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    (Original post by mackin boi)
    not for edexcel

    then why the hell has my teacher been teaching us this then????? :mad:


    lol...
 
 
 
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