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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD

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Original post by marioman
Table of peaks!



Do u mean like this one (from the June 2015 MS)
What colums are u doing for 13C NMR and also won't you need another column for what the relative peak area tells u like e.g. relative peak area of 3 indicates CH3
Original post by itsConnor_
Even if you're not saying 'relative peak area of 3 indicates 3 hydrogens in this environment' and 'triplet indicates 2 hydrogens on the adjacent carbon' etc. ?


In that particular mark scheme the first 4 marks are just for identifying the correct environments and linking them to the shift values. The fifth mark is for using either the triplet or the quartet peak to deduce that the molecule contains CH2CH3. The sixth mark is for identifying R1 as CH3, and the final mark is for the correct structure of R2.
Original post by yoda123

Do u mean like this one (from the June 2015 MS)
What colums are u doing for 13C NMR and also won't you need another column for what the relative peak area tells u like e.g. relative peak area of 3 indicates CH3


When I do it I usually add an extra column for 'notes', tying together the different pieces of data each peak gives you.

For 13C NMR I usually don't bother with a table as there is no splitting patterns/relative peak area. I just annotate the spectrum (this scores marks) with the environment represented by each peak.
Original post by marioman
In that particular mark scheme the first 4 marks are just for identifying the correct environments and linking them to the shift values. The fifth mark is for using either the triplet or the quartet peak to deduce that the molecule contains CH2CH3. The sixth mark is for identifying R1 as CH3, and the final mark is for the correct structure of R2.


isnt that playing a bit of a dangerous game? also if you do the 'notes' column do you have enough space? :smile:
Original post by itsConnor_
isnt that playing a bit of a dangerous game? also if you do the 'notes' column do you have enough space? :smile:


f324-Jun15.pngThis is an extract from an OCR presentation featuring some real candidate answers from the exam. This response was awarded all 7 marks with minimal writing, just a table and diagrams! (I wonder if they were a poster on this site)
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AqsaMx
5
Original post by RayMasterio
Which paper is this? I want to attempt it myself.


No idea, at the bottom it says 2009 OCR so yeah. When you figure it out, pls let me know
Reply 886
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AqsaMx
5
Original post by AqsaMx
image.jpeg

Can anyone explain the relative heights question? What's it even asking?


Anyone know ?
this man has a good method as well for NMR
https://www.youtube.com/watch?v=UuEfvamQrP4&list=PLi6oabjl6cozRJ83zxoa0_QFqJpMHLWYJ&index=6
(edited 7 years ago)
Original post by AqsaMx
Anyone know ?


I think the height of the peak at 122 m/e would be greater as it does not contain the isotope so is more abundant? Not really sure though

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sophay_
Please can someone help me with acid hydrolysis of polypeptides / polyamides? In the revision guide it says it forms, for example, a dicarboxylic acid and a diamine. However, e.g. in question 6b of June 2011, the acid hydrolysis forms -NH3+ instead of -NH2. Is there a different rule or is the textbook wrong? If this makes sense to anyone please help :'(
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ranz
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Original post by yoda123


i want to use the table but im not used to it, but i guess its good because its also good to overview


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Original post by sophay_
Please can someone help me with acid hydrolysis of polypeptides / polyamides? In the revision guide it says it forms, for example, a dicarboxylic acid and a diamine. However, e.g. in question 6b of June 2011, the acid hydrolysis forms -NH3+ instead of -NH2. Is there a different rule or is the textbook wrong? If this makes sense to anyone please help :'(


it is nh3+
and in alkaline hydrolysis u get the COO-NA+
Reply 892
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sophay_
Original post by yoda123
it is nh3+
and in alkaline hydrolysis u get the COO-NA+


Okay, thank you!! I'll just ignore the book haha
Original post by Yazmin123
what do you guys think is gonna come up for the NMR imagine if they ask us to draw one- bye


I think it'll be something we've never really seen before like an amine group, amide link or maybe it'll contain a halogen group?

I really hope we don't have to be sketching the NMR spectrum ourselves though :/
Reply 894
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ranz
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ive accepted that i wont be able to finish nmr correctly, every single past paper ive done i somehow manage to screw up the final structure! i just dont know how to add them together! like a puzzle 😭😭


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Original post by marioman
f324-Jun15.pngThis is an extract from an OCR presentation featuring some real candidate answers from the exam. This response was awarded all 7 marks with minimal writing, just a table and diagrams! (I wonder if they were a poster on this site)


Sorry where is the presentation? :smile:
Reply 896
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ranz
5
guys does this have any significance:

"in the proton nmr spectrum, the peak at xx would normally be expected at a chemical ahift value about e right" what does this mean?


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Original post by ranz
ive accepted that i wont be able to finish nmr correctly, every single past paper ive done i somehow manage to screw up the final structure! i just dont know how to add them together! like a puzzle 😭😭


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Don't panic in the exam, remember you can get most of the marks without a correct structure :smile:
Original post by ranz
guys does this have any significance:

"in the proton nmr spectrum, the peak at xx would normally be expected at a chemical ahift value about e right" what does this mean?


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Look at the splitting pattern and then refer to the chemical shift in the data sheet ONE to the right (e.g. if 3.4 on spectrum, look at 2.4 in data sheet) i think
Original post by ranz
guys does this have any significance:

"in the proton nmr spectrum, the peak at xx would normally be expected at a chemical ahift value about e right" what does this mean?


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Assume the chemical shift is at where it indicates.

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