C13 Nmr

[tank you]

on aamc 8, there was one cnmr question. i just guessed since the carbonyl carbon was closest to the oxygen, it would shift the farthest, so i got the question correct, but do we have to know other shifts for C13 NMR?

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[Fups]

no, i dont think we need to know much more about it. i did the same as you did, just sort of reasoned it out, and got it correct also. the AAMC will throw us a few curve balls like that, but I'm sure if we reason it out logically using the knowledge that we have, we should be able to guess correctly on other random questions... like we did.

 

[dilated]

The real key to the question is that C13 NMR is almost exactly the same as H1 NMR (you can even tell splitting if you don't set the machine to decouple). Thus, since you (presumably) know that, for example, an aldehyde is very far downfield due to the loss of electron density, you can basically just apply that to the carbon that it's attached to.

 

[natureboy]

Ha! I did the same as both of you and just went along with that logic and also got it right. If there is a C NMR on the MCAT, I would highly doubt that it will be more than one question, at least that's according to EK.

Now I am curious: anyone here taken the MCAT and gotten more than one C NMR question before?