How do you label 1H and 13C NMR environments?

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Lena_277
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The OCR textbook gives the example of COOHCH(CH3)COOH (chromatography and spectroscopy practise Qs), and the question (5b) asks to predict the 1H NMR spectrum. In the answer, they give the peaks and splitting pattern (which I know how to work out), but when labelling each one they give some strange version of a structural formula to refer to the non-equivalent C atoms which produces each peak. They seem to assume that its obvious where they get it from, but I just don't get it!:

singlet caused by COOH
quartet caused by COCHCO (with adjacent CH3)
doublet caused by CCH3 (with adjacent CH)

Where does COCHCO come from?? How do you know which atoms to include?

Hope this makes sense and sorry for the lengthiness of it...
Last edited by Lena_277; 1 year ago
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charco
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(Original post by Lena_277)
The OCR textbook gives the example of COOHCH(CH3)COOH (chromatography and spectroscopy practise Qs), and the question (5b) asks to predict the 1H NMR spectrum. In the answer, they give the peaks and splitting pattern (which I know how to work out), but when labelling each one they give some strange version of a structural formula to refer to the non-equivalent C atoms which produces each peak. They seem to assume that its obvious where they get it from, but I just don't get it!:

singlet caused by COOH
quartet caused by COCHCO (with adjacent CH3)
doublet caused by CCH3 (with adjacent CH)

Where does COCHCO come from?? How do you know which atoms to include?

Hope this makes sense and sorry for the lengthiness of it...
If you draw out the displayed structural formula of the compound you will see exactly where the "parts" come from.

.. or should that be, "from where the parts come" (avoiding prepositions at the end of a sentence).

COOH should really be written HOOC.

So the structure is: HOOC- CH(CH3)-COOH
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Lena_277
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(Original post by charco)
If you draw out the displayed structural formula of the compound you will see exactly where the "parts" come from.

.. or should that be, "from where the parts come" (avoiding prepositions at the end of a sentence).

COOH should really be written HOOC.

So the structure is: HOOC- CH(CH3)-COOH
Thanks for your reply (and for the grammar corrections!). Just one more question: does it matter if you write C–CH3 or CCH3?
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charco
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(Original post by Lena_277)
Thanks for your reply (and for the grammar corrections!). Just one more question: does it matter if you write C–CH3 or CCH3?
It does not really matter unless you are specifically asked to do it. Although it is difficult to imagine a case in which this would be so.
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Lena_277
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(Original post by charco)
It does not really matter unless you are specifically asked to do it. Although it is difficult to imagine a case in which this would be so.
OK, thanks
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