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Chemistry NMR Spectra

Hi, I was doing a question on proton NMR and it said that the product of the reaction between methylpropanoyl chloride and ethanol would have a doublet at 2.5ppm in its proton NMR.

I'd assume the product would by ethyl 2-methylpropanoate, which would have a multiplet between 2.1 and 2.6 as the C-H beside the C=O has 2 CH3 groups attached to it, hence causing it to not be a doublet.

What would the doublet be caused by, and additionally, how come it is ethyl 2-methylpropanoate instead of ethyl methylpropanoate?

Thank you :smile:
The doublet will caused by the 2x CH3 environments and will be split by the proximity to the CH environment adjacent to the C=O.
Reply 2
Original post by Pigster
The doublet will caused by the 2x CH3 environments and will be split by the proximity to the CH environment adjacent to the C=O.


Thank you!

How would I be meant to know that the CH3 environments would be affected by the C=O despite not being adjacent to it, since the data sheet doesn't really suggest this?

Thank you for you help!
Original post by Cuspake
Thank you!

How would I be meant to know that the CH3 environments would be affected by the C=O despite not being adjacent to it, since the data sheet doesn't really suggest this?

Thank you for you help!

The CH3's are not adjacent to the C=O and hence would have a shift value of 1-2 since they are HC-R.
Reply 4
Original post by Pigster
The CH3's are not adjacent to the C=O and hence would have a shift value of 1-2 since they are HC-R.


Oh okay, thanks. How come it's a doublet for the CH, as there are 6 H beside it?
(edited 1 year ago)
Reply 5
Original post by Cuspake
Oh okay, thanks. How come it's a doublet for the CH, as there are 6 H beside it?

That's one of the main things that confused me
(edited 1 year ago)
Original post by Cuspake
Oh okay, thanks. How come it's a doublet for the CH, as there are 6 H beside it?


You missed my point. The CH will be a heptet, split by the 6xHs

The 6xHs are all in the same environment and will be split by the CH as a doublet.
Reply 7
Original post by Pigster
You missed my point. The CH will be a heptet, split by the 6xHs

The 6xHs are all in the same environment and will be split by the CH as a doublet.


What would the ppm be for the doublet?
Original post by Cuspake
What would the ppm be for the doublet?


What do you think?
Reply 9
Original post by Pigster
What do you think?

0.7 - 1.2 As it's an RCH3?
Original post by Cuspake
0.7 - 1.2 As it's an RCH3?


Curiously, the AIST NMR database isn't working at the moment.

The NMR predictor that I use suggests that ethyl methylpropanoate should have:

peak @ 1-2 int = 6 doublet (you're right it shouldn't be 2.3)
@ 1-2 int = 3 triplet
@2-3 int = 1 heptet
@3-4 int = 2 quartet.

Sorry for not spotting earlier your problem. You're right the Q is wonky IMO. Where is it Q from?
Reply 11
Original post by Pigster
Curiously, the AIST NMR database isn't working at the moment.

The NMR predictor that I use suggests that ethyl methylpropanoate should have:

peak @ 1-2 int = 6 doublet (you're right it shouldn't be 2.3)
@ 1-2 int = 3 triplet
@2-3 int = 1 heptet
@3-4 int = 2 quartet.

Sorry for not spotting earlier your problem. You're right the Q is wonky IMO. Where is it Q from?


No worries at all, thank you for being so patient!

It's an old spec paper, so maybe it uses different values. Thank you for your reassurance though, I was really confused earlier!
Reply 12
Original post by Cuspake
No worries at all, thank you for being so patient!

It's an old spec paper, so maybe it uses different values. Thank you for your reassurance though, I was really confused earlier!


Found it; I was confused as to whether it would be B or D as both seemed to be incorrect, and now I know that's true, thanks!

https://www.a-levelchemistry.co.uk/a-level-assessment-points-and-practice-papers.html
A Level Paper 3 Practice Paper 11 (specific question attached for ease)

TSR nmr.png

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