Functional group peak splitting

[kenhung123]

Do the hydrogens on the same carbon which contain a functional group split adjacent CH groups?

This is the NMR spec when it does. Is it wrong?

[Blakhitman]

Yeah that's right.

[Potter]

I'm quite sure the NMR you drew up is incorrect. Though, it doesn't really matter since the examiners would never ask you to identify a molecule like that.
Reason being is that you have that -CH2- between two other hydrogen environments. What happens is that the splitting becomes more complicated(I think you get 12 peaks for that -CH2-). You do not count the protons on surrounding carbons and then add 1! Feel free to correct me if I'm wrong as my understanding isn't as sound as others.

So yeah, the molecules that examiners give to students on exams cannot be too complicated otherwise the spectra's go out of whack and beyond scope.

[Akirus]

I'm quite sure the NMR you drew up is incorrect. Though, it doesn't really matter since the examiners would never ask you to identify a molecule like that.
Reason being is that you have that -CH2- between two other hydrogen environments. What happens is that the splitting becomes more complicated(I think you get 12 peaks for that -CH2-). You do not count the protons on surrounding carbons and then add 1! Feel free to correct me if I'm wrong as my understanding isn't as sound as others.

So yeah, the molecules that examiners give to students on exams cannot be too complicated otherwise the spectra's go out of whack and beyond scope.

That's consistent with what my chem teacher told us.

[kenhung123]

I'm quite sure the NMR you drew up is incorrect. Though, it doesn't really matter since the examiners would never ask you to identify a molecule like that.
Reason being is that you have that -CH2- between two other hydrogen environments. What happens is that the splitting becomes more complicated(I think you get 12 peaks for that -CH2-). You do not count the protons on surrounding carbons and then add 1! Feel free to correct me if I'm wrong as my understanding isn't as sound as others.

So yeah, the molecules that examiners give to students on exams cannot be too complicated otherwise the spectra's go out of whack and beyond scope.

I don't understand how you got 12? Why isn't it just adding hydrogens on adjacent carbon groups?

[chem-nerd]

because they are not all equivalent (ie the CH3 neighbours are not equivalent to the CH2 neighbours) hence it's not 5 + 1 peaks

[Mao]

Technically, Potter and chem-nerd are correct, it splits into 12 peaks.

However, these 12 peaks will invariably look very similar to a sextet. This is since the splitting frequency [the separation between sub-peaks] between two neighbouring alkyl groups is roughly constant [i.e. CH3 will split the CH2 to the same 'separation' as the CH2OH splits CH2], thus overlapping occurs, and you will get something very close to a sextet (with the peaks split by tiny amounts at the tip). Unless you zoom in really really close, you probably won't be able to identify the 12 distinct peaks.

For the sake of VCE, I wouldn't worry too much about it. You definitely need to be aware of this multiplicity, but you also need to be aware it's not always very practical.

[excuse my horrible wordings]

[kyzoo]

xD I just learned about this multiplicity thing today.

Is it possible to get more than 36 peaks?
H in the -CH group in CH3CH(CH2OH)CH2NH2

[kenhung123]

I think I am missing some knowledge in NMR. I always though H NMR shows how many hydrogens are adjacent the a particular CH group e.g. 5 splits means adjacent CH3 and CH or CH2 and CH2 (1 split due to the carbon under analysis). Also I know that if a molecular is symmetrical, the central CH group does not get split twice e.g. CH3-CH2-CH2-CH3 the CH2 would be split in 4 only (CH2 parent peak+3 peak due to adjacent CH3)