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f324

june 2015 q 4 NMR, how do you count the H environments on the benzene, i keep counting 8 not 5.
Original post by Melina18
june 2015 q 4 NMR, how do you count the H environments on the benzene, i keep counting 8 not 5.


It's not possible to have 8 environments on benzene - it's only got 6 hydrogen atoms (and they are all in one environment)
Reply 2
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alow
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Post the question.
Reply 3
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Melina18
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Original post by charco
It's not possible to have 8 environments on benzene - it's only got 6 hydrogen atoms (and they are all in one environment)


sorry i don't mean just on the benzene, the molecule has two benzene rings in it. but in the whole molecule i keep counting 8 proton environments but i know theres only 5 because there are only 5 peaks on the spectrum. i don't know where im going wrong.
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Melina18
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Original post by alow
Post the question.


its the last question
F324-01 QP Jun15.pdf544.2KB
Reply 5
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lolo11
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Often with benzene, the aromatic protons are grouped in the same environment in the NMR spectrum due to their close proximity to one another. For this question there are 7 aromatic protons, three of which refer to the benzene ring making up the 2,4-DNPH molecule, and the remaining four which make up the benzene ring for one of the side chains.

I'm not quite sure I understand why you think there are 8 proton environments, or why you think the correct answer is 5?!
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Melina18
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Original post by lolo11
Often with benzene, the aromatic protons are grouped in the same environment in the NMR spectrum due to their close proximity to one another. For this question there are 7 aromatic protons, three of which refer to the benzene ring making up the 2,4-DNPH molecule, and the remaining four which make up the benzene ring for one of the side chains.

I'm not quite sure I understand why you think there are 8 proton environments, or why you think the correct answer is 5?!


the correct number of hydrogen environments is 5 because there are 5 peaks on the proton NMR, i was counting 8 in the final answer (where you deduce the R groups)Photo on 12-06-2016 at 20.10.jpg
Attachment not found
theres a photo of the molecule and its proton NMR
i checked to see if the last peak at around 7 was meant to be 2 separate peaks but its not.
Photo on 12-06-2016 at 20.10 #2.jpg94.4KB
Reply 7
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Yes so from the spectrum there are five different proton environments in total as there are five different peaks. The peak(s) at approximately 7.1-7.5 ppm are the aromatic protons. Like I said above due to their close proximity there is an overlap in peaks so the peaks for the aromatic protons will appear close together. The integration value is 7 for this peak so there are 7 aromatic protons- 3 of which are from the benzene ring making up the 2,4-DNPH molecule and the other four make up the side chain. Does this make sense or is this irrelevant to your question?
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Melina18
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Original post by lolo11
Yes so from the spectrum there are five different proton environments in total as there are five different peaks. The peak(s) at approximately 7.1-7.5 ppm are the aromatic protons. Like I said above due to their close proximity there is an overlap in peaks so the peaks for the aromatic protons will appear close together. The integration value is 7 for this peak so there are 7 aromatic protons- 3 of which are from the benzene ring making up the 2,4-DNPH molecule and the other four make up the side chain. Does this make sense or is this irrelevant to your question?


ohh i see, yeah that makes sense thankyou so much. :smile:
Reply 9
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lolo11
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No problem. Good luck for tomorrow! :smile:
Original post by Melina18
june 2015 q 4 NMR, how do you count the H environments on the benzene, i keep counting 8 not 5.


There are two benzene rings. Hence 8 aromatic protons. If you're still stumped on this question watch this-
https://www.youtube.com/watch?v=UuEfvamQrP4
(edited 7 years ago)
Reply 11
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Original post by GEEKSruletheworld!
There are two benzene rings. Hence 8 aromatic protons. If you're still stumped on this question watch this-
https://www.youtube.com/watch?v=UuEfvamQrP4


thankyou! video was really helpful :smile:
how did you guys find the actual exam today ?
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Bgxx
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Not good wbu
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Sean9090
Original post by Derek12353
how did you guys find the actual exam today ?


Went very well so happy there was an easy 7 mark question over a proton NMR to guess I'd say I've got around 54/60
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Original post by Sean9090
Went very well so happy there was an easy 7 mark question over a proton NMR to guess I'd say I've got around 54/60


yeah i found it alright, thinking back i know i messed up the cyclic ester one....so annoying, what do you think the grade boundries will be like?
Reply 16
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Original post by Bgxx
Not good wbu


what parts did you find difficult? you can make up the marks on the next paper tho! dont worry about it
on the scale of things was probably one of the easier exams that they have given us hopefully they wont try and ***** slap us on f325
Reply 18
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Melina18
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Original post by Derek12353
on the scale of things was probably one of the easier exams that they have given us hopefully they wont try and ***** slap us on f325

yeahh! ive got a feeling they're going to put something nasty in f325. do you do biology too???

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