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OCR F324-June 2013 Chemistry

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Original post by otrivine
:smile:


Suggest why amino acids have isoelectric points (1)


Because they are amphoteric and have both a basic and acidic group so they are known as a zwitterion and when an amino acid acts as a zwitterion it has an isoelectric point.


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Original post by MathsNerd1
Because they are amphoteric and have both a basic and acidic group so they are known as a zwitterion and when an amino acid acts as a zwitterion it has an isoelectric point.


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perfecto


my turn :smile:
Original post by otrivine
perfecto


my turn :smile:


Here you go. Enjoy :tongue: (6)



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Original post by MathsNerd1
Here you go. Enjoy :tongue: (6)



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Can I have another one please I did this already! can you make one
Original post by otrivine
Can I have another one please I did this already! can you make one


Erm, it's hard to think of my own as I've only just gotten back, are there any concepts of NMR that you're struggling to understand?


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Original post by MathsNerd1
Erm, it's hard to think of my own as I've only just gotten back, are there any concepts of NMR that you're struggling to understand?


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on question 5)c)ii) page 108 , I do not get why there are 4 protons?
Original post by otrivine
on question 5)c)ii) page 108 , I do not get why there are 4 protons?


Isn't it because on the lactic acid there are 2 OH bonds but they are in different proton environments so they'll be two different peaks for them making the 4 overall with the original two?


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Original post by MathsNerd1
Isn't it because on the lactic acid there are 2 OH bonds but they are in different proton environments so they'll be two different peaks for them making the 4 overall with the original two?


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I thought because D2O causes the hydrogen in OH to be replaced with a D and therefore, when the hydrogen is replaced with D there should be 2 proton exchange ?
Original post by otrivine
I thought because D2O causes the hydrogen in OH to be replaced with a D and therefore, when the hydrogen is replaced with D there should be 2 proton exchange ?


Hmm well the way I remember it is that a D2O shake removes any OH or NH peaks from a proton NMR spectrum, so if its asking you how many you'd see if it was run in a inert solvent then that solvent won't be able to interfere with the compound and because they were in different environments you'll get two separate peaks produced, does this help in any way?


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Original post by MathsNerd1
Hmm well the way I remember it is that a D2O shake removes any OH or NH peaks from a proton NMR spectrum, so if its asking you how many you'd see if it was run in a inert solvent then that solvent won't be able to interfere with the compound and because they were in different environments you'll get two separate peaks produced, does this help in any way?


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so 2 different peaks means 2 exchanged not 4?

How do you if a proton is in same environment or not.
Original post by otrivine
so 2 different peaks means 2 exchanged not 4?

How do you if a proton is in same environment or not.


Hmm I'm not entirely sure as I never truly got taught about the D2O except from the fact that it removes the OH peaks off the spectrum.

Secondly wouldn't you look at the adjacent protons and normally they are in the same environment if they have the same amount of adjacent protons and also if they have the same carbon atoms around them.


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Original post by MathsNerd1
Hmm I'm not entirely sure as I never truly got taught about the D2O except from the fact that it removes the OH peaks off the spectrum.

Secondly wouldn't you look at the adjacent protons and normally they are in the same environment if they have the same amount of adjacent protons and also if they have the same carbon atoms around them.


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I am dying, this proton NMR is making me stressed now :frown: ok! do you have questions to ask me!? please, or can you use questions in your class:s-smilie:
Original post by otrivine
I am dying, this proton NMR is making me stressed now :frown: ok! do you have questions to ask me!? please, or can you use questions in your class:s-smilie:


Well in my opinion if its stressing you out you should take a break from it, then when you feel like you're ready to take it on again then start over, but it is meant to be quite a hard concept to get to grips, I don't think more questions will help you and I'm very bad at explaining it since I have hardly been taught it, I just know what to do when approaching the questions.


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Original post by MathsNerd1
Well in my opinion if its stressing you out you should take a break from it, then when you feel like you're ready to take it on again then start over, but it is meant to be quite a hard concept to get to grips, I don't think more questions will help you and I'm very bad at explaining it since I have hardly been taught it, I just know what to do when approaching the questions.


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I am ready, now had a break after watching my idol Nicki Minaj :smile:
Original post by otrivine
I am ready, now had a break after watching my idol Nicki Minaj :smile:


Okay, draw both the C-13 and proton spectrums for propyl ethanoate. (6)


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Original post by MathsNerd1
Okay, draw both the C-13 and proton spectrums for propyl ethanoate. (6)


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I will only do proton NMR , as today I only spent time on proton!
Original post by otrivine
I will only do proton NMR , as today I only spent time on proton!


Okay but have you done C-13 NMR before trying to do proton NMR?


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Original post by MathsNerd1
Okay but have you done C-13 NMR before trying to do proton NMR?


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No literally, I start with proton NMR then do carbon then do lastly chromatography
Original post by otrivine
No literally, I start with proton NMR then do carbon then do lastly chromatography


Okay well I would strongly advise you to do C-13 NMR before carrying on with proton as it'll confuse you less as you've basically went straight for the hard part without learning to basics to it, like how you can identify them being in different environments and such. Chromatography is quite a pain for me, bloody awful actually!


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Original post by MathsNerd1
Okay well I would strongly advise you to do C-13 NMR before carrying on with proton as it'll confuse you less as you've basically went straight for the hard part without learning to basics to it, like how you can identify them being in different environments and such. Chromatography is quite a pain for me, bloody awful actually!


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My scanner is not working now! Can I see the answer please!

ok ill tell you what I got

in the sketch I did the y axis being the chemical shift,ppm

I got singlet,quartet,triplet,multiplet and a triplet

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