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    Can anyone remind me just what COSY NMR is supposed to indicate regarding the protons in a system? I'm trying to find a clear and concise description but wikipedia isn't too helpful
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    (Original post by Charzhino)
    Can anyone remind me just what COSY NMR is supposed to indicate regarding the protons in a system? I'm trying to find a clear and concise description but wikipedia isn't too helpful
    it is correlated spectroscopy, so it involves 2D NMR placed on the x and y-axes.

    it correlates homonuclear atoms that are bonded directly in 1 bond coupling, but you could also do heteronuclear correlated NMR.

    these could be further extended for multi bond coupling to identify atoms close in space for coupling to be seen, as an alternative or addition to nOe experiments to confirm/identify 3D picture of a molecule.
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    (Original post by shengoc)
    it is correlated spectroscopy, so it involves 2D NMR placed on the x and y-axes.

    it correlates homonuclear atoms that are bonded directly in 1 bond coupling, but you could also do heteronuclear correlated NMR.

    these could be further extended for multi bond coupling to identify atoms close in space for coupling to be seen, as an alternative or addition to nOe experiments to confirm/identify 3D picture of a molecule.
    Im not sure what you mean by 1 bond coupling, isnt that what regular NMR does? I have seen somewhere that it can correlate through 4 bond distance but Im not sure if it is COSY. So can I use COSY NMR to assign specific protons on my napthlene functionalised molecule for example?
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    (Original post by Charzhino)
    Im not sure what you mean by 1 bond coupling, isnt that what regular NMR does? I have seen somewhere that it can correlate through 4 bond distance but Im not sure if it is COSY. So can I use COSY NMR to assign specific protons on my napthlene functionalised molecule for example?
    yes, normal 1 bond coupling is seen in the conventional NMR. but to correlate them with another NMR data on the other axes, you can see which atoms are connected to which atoms, and hence the idea of correlation.

    there are different lots of abbreviations for these techniques, some are listed here
    http://en.wikipedia.org/wiki/Correlation_spectroscopy

    i don't see why you can't use COSY NMR to do correlation for any organic molecule. though i would presume a 13-C proton decoupled COSY would be cleaner here and in most COSY cases
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    (Original post by Charzhino)
    Im not sure what you mean by 1 bond coupling, isnt that what regular NMR does? I have seen somewhere that it can correlate through 4 bond distance but Im not sure if it is COSY. So can I use COSY NMR to assign specific protons on my napthlene functionalised molecule for example?
    I'm not an expert on NMR but you can see more than 1-bond coupling in a COSY. For example, two protons on an aromatic ring coupling with a small W-coupling 4JHH constant would show usually up on the COSY.

    In practice what you get is a series of dots of varying thickness with a strong diagonal on the COSY since both axes are the same hydrogen spectrum. The thick dots usually indicate strong coupling and/or high concentration in sample. A COSY is mainly useful for correlating protons that don't have an obvious coupling pattern in the one-dimensional spectrum (such as multiplets).

    An HMQC shows the correlation of hydrogens and protons so is mainly used to assign 13C NMR and an HMBC gives you longer-range interactions. NOESY pick up through-space interactions and so are used for things like diastereomer assignments of substituted cyclohexanes etc.
 
 
 
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