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NMR spectrum question alevel chemistry aqa

Two isomers of CH3CHClCOCH(CH3)2 each have two singlet peaks only in
their 1H NMR spectra.
In both spectra the integration ratio for the two peaks is 2:9
Deduce the structures of these two isomers.

would it be correct if i gave the 2nd isomer as the carbon in C=O being bonded to an H as well rather than the C=O bonded to a Cl? my first isomer was the same as drawn in the MS.
MS:https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FChemistry%2FA-level%2FTopic-Qs%2FAQA%2FOrganic-II%2F3.15-NMR-Spectroscopy%2FSet-I%2FNMR%20Spectroscopy%20MS.pdf page 3

Reply 1

Original post
by ricecakes1
Two isomers of CH3CHClCOCH(CH3)2 each have two singlet peaks only in
their 1H NMR spectra.
In both spectra the integration ratio for the two peaks is 2:9
Deduce the structures of these two isomers.
would it be correct if i gave the 2nd isomer as the carbon in C=O being bonded to an H as well rather than the C=O bonded to a Cl? my first isomer was the same as drawn in the MS.
MS:https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FChemistry%2FA-level%2FTopic-Qs%2FAQA%2FOrganic-II%2F3.15-NMR-Spectroscopy%2FSet-I%2FNMR%20Spectroscopy%20MS.pdf page 3

No, because then you would have two signals each corresponding to one proton, which would make it impossible to get a 9:2 ratio of peak integrals (you’d need a proton environment corresponding to 4.5 protons for that to be possible, but you can only have a whole number of protons per environment).

Additionally, you would have three proton environments and two of the signals would not be singlets (you would think there should be two doublets - one corresponding to the chiral CHCl environment and the other corresponding to the CHO proton, though the reality is that it is a bit more complicated).
(edited 11 months ago)

Reply 2

Original post
by TypicalNerd
No, because then you would have two signals each corresponding to one proton, which would make it impossible to get a 9:2 ratio of peak integrals (you’d need a proton environment corresponding to 4.5 protons for that to be possible, but you can only have a whole number of protons per environment).
Additionally, you would have three proton environments and two of the signals would not be singlets (you would think there should be two doublets - one corresponding to the chiral CHCl environment and the other corresponding to the CHO proton, though the reality is that it is a bit more complicated).

thanks!

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