For peaks between 2 and 3, there is uncertainty, so ignore them initially, and deduce other peaks instead, than come back to them. For D2O shake, it removes all H bonded to O and all H bonded to N. For joining the peaks together, use the pairing - the number of H on adjacent carbons. When we did this last year, first we made an information table of each peak… than we had to join them using pairing. Practice doing NMR will help you gain experience to pair things better and faster - as you notice patterns. A peak at 7 is benzene, with the multiplet, which is helpful. It makes the peak at 2 to 3, easier, especially as you know the relative area.
Sometimes, you see a peak at 1 with relative area 9. What does this mean…
It means C(CH3)3, 3 CH3 bonded to a single C, this is from experience.
Notice that it said a possible structure, if it gave a C13 NMR as well, we could work out the carbon environments…
A NMR question will always come with additional things you will need to do:
Find empirical formula, molecular formula, use IR spectrum (functional groups), use mass spectrum (fragment ions, M+ peak), H NMR, C NMR, H NMR with and without D2O…
(edited 8 months ago)
Original post by BankaiGintoki
For peaks between 2 and 3, there is uncertainty, so ignore them initially, and deduce other peaks instead, than come back to them. For D2O shake, it removes all H bonded to O and all H bonded to N. For joining the peaks together, use the pairing - the number of H on adjacent carbons. When we did this last year, first we made an information table of each peak… than we had to join them using pairing. Practice doing NMR will help you gain experience to pair things better and faster - as you notice patterns. A peak at 7 is benzene, with the multiplet, which is helpful. It makes the peak at 2 to 3, easier, especially as you know the relative area.
Sometimes, you see a peak at 1 with relative area 9. What does this mean…
It means C(CH3)3, 3 CH3 bonded to a single C, this is from experience.
Notice that it said a possible structure, if it gave a C13 NMR as well, we could work out the carbon environments…
A NMR question will always come with additional things you will need to do:
Find empirical formula, molecular formula, use IR spectrum (functional groups), use mass spectrum (fragment ions, M+ peak), H NMR, C NMR, H NMR with and without D2O…
For peaks between 2 and 3, there is uncertainty, so ignore them initially, and deduce other peaks instead, than come back to them. For D2O shake, it removes all H bonded to O and all H bonded to N. For joining the peaks together, use the pairing - the number of H on adjacent carbons. When we did this last year, first we made an information table of each peak… than we had to join them using pairing. Practice doing NMR will help you gain experience to pair things better and faster - as you notice patterns. A peak at 7 is benzene, with the multiplet, which is helpful. It makes the peak at 2 to 3, easier, especially as you know the relative area.
Sometimes, you see a peak at 1 with relative area 9. What does this mean…
It means C(CH3)3, 3 CH3 bonded to a single C, this is from experience.
Notice that it said a possible structure, if it gave a C13 NMR as well, we could work out the carbon environments…
A NMR question will always come with additional things you will need to do:
Find empirical formula, molecular formula, use IR spectrum (functional groups), use mass spectrum (fragment ions, M+ peak), H NMR, C NMR, H NMR with and without D2O…
Thank you for giving a laid out answer, and explaining everything you did! Next time I think I'll try the table method to link peaks together.
Original post by 0gg
(OCR A) What's your strategy for tackling those big 6 mark questions with a 1H NMR? I can usually get there in the end, but my method feels like such a mess, and finding pieces of the molecule that fit together feels like shots in the dark.
Any help is great
Any help is great
Work out your structure before you write in the answer space. Since the communication mark is essentially for writing your answer in a way that they can read and understand it, you don't want to be working out your answer in the space for writing your answer.
For example - the peaks between 2 and 3 could be either HC-C=O OR HC-C6H5 OR HC-N OR HO OR H2N ... so rather than wafflling about the fact that they could be lots of different things, work out what they actually are in advance of writing your answer and simply write what they are e.g. peak @ 2.3 = HC-C6H4 AND peak @ 2.7 = HC-C=O
BULLET POINT YOUR ANSWER. You aren't allowed to use bullet points... you should do it. It makes it easier and quicker for you and easier and quicker for the examiner to mark it.
If you want some help with working out structures, try here: http://drrichardmusgrave.com/nmr-exercises-with-structure-builder (the bit about DBE isn't needed for OCR A, but you'll quickly get your head around it - if you can't you're welcome to ask for help)
Original post by 0gg
(OCR A) What's your strategy for tackling those big 6 mark questions with a 1H NMR? I can usually get there in the end, but my method feels like such a mess, and finding pieces of the molecule that fit together feels like shots in the dark.
Any help is great
Any help is great
Proton NMR was the bane of my existence when I was doing A level chemistry. There are a few tips you can follow so that it feels more logical.
First I would recommend watching all the Machem guy videos on Proton NMR as he explains the steps required to get to the correct answer. I guess its also normal to feel like there is no logic to it as its meant to be trail and error, seeing if the structures that you made up fit with the data provided.
Keep doing loads of practice questions on proton NMR, repeat the question until you get it correct.#
Also if you want any more help in chemistry please feel free to pm me
(edited 7 months ago)
Original post by foreverrocking2
Proton NMR was the bane of my existence when I was doing A level chemistry.
Ahaha I love it. I will definitely check out his videos.
There have been some good answers on this thread, I hope it can help anyone else with the same problem (:
Original post by 0gg
There have been some good answers on this thread, I hope it can help anyone else with the same problem (:
Hello @0gg,
Thank you for posting in the Chemistry Forum.
I'm glad to hear that you have found the answers useful on this thread.
Good luck with A-Level Chemistry.
Shyleen
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