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    Name:  image.jpg
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Size:  503.2 KBHow to distinguish between two singlet and one doublet? I thought these were two singlets but the answer is one doublet
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    See how many environments your product has, compare that to the spectrum. See if the difference between the two picks is reasonable for the environment you have assigned.
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    (Original post by mystreet091234)
    Name:  image.jpg
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Size:  503.2 KBHow to distinguish between two singlet and one doublet? I thought these were two singlets but the answer is one doublet
    One clue is the slight difference in height of the doublet signal at higher ppm value - suggesting that there is coupling with another proton further downfield.
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    (Original post by charco)
    One clue is the slight difference in height of the doublet signal at higher ppm value - suggesting that there is coupling with another proton further downfield.
    Shouldn't the two lines have equal intensities if they are a doublet?
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    They're very close together with similar heights.
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    (Original post by mystreet091234)
    Shouldn't the two lines have equal intensities if they are a doublet?
    Not necessarily, no. The height can change dependent on which environment it is coupling with.
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    (Original post by mystreet091234)
    Shouldn't the two lines have equal intensities if they are a doublet?
    Yes, but there is a tendency for distortion towards the group that they are coupled with.

    So if you have a CH3 attached to a CH2 there will be a triplet and a quartet. The peak of the triplet closest to the quartet will be slightly larger than the one furthest away. Likewise with the quartet peak closest to the triplet.

    Look at the spectrum of ethanol:



    It is a phenomenon that is not 100% reliable but can give clues as to which signals are coupled together if you can't measure the coupling constants.
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    Thank you so much for all the detailed explanation
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    (Original post by charco)
    One clue is the slight difference in height of the doublet signal at higher ppm value - suggesting that there is coupling with another proton further downfield.
    Downfield terminology? How old are you?
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    (Original post by Infraspecies)
    Downfield terminology? How old are you?
    What?
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    (Original post by Infraspecies)
    Downfield terminology? How old are you?
    Younger than my teeth ...

    ... although to be fair, you understood!
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    (Original post by alow)
    What?
    The upfield/downfield terminology is only a remnant of the old ways that NMR spectra are obtained, and the concept doesn't apply to modern spectra. In general, it's obfuscating the physical concepts behind NMR to use properly obsolete language.
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    (Original post by charco)
    Younger than my teeth ...

    ... although to be fair, you understood!
    Because I've been taught to spot the dangers the older academic population represent :P
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    (Original post by Infraspecies)
    The upfield/downfield terminology is only a remnant of the old ways that NMR spectra are obtained, and the concept doesn't apply to modern spectra. In general, it's obfuscating the physical concepts behind NMR to use properly obsolete language.
    kill joy ...
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    (Original post by charco)
    kill joy ...
    Four years of angry and bitter academics ranting about how they despise it leaves a mark on a person :,(
 
 
 
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