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OCR F324 (Chains, rings and spectroscopy) 28/06/10

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Reply 780
Avatar for Noble.
Noble.
17
_Andrew_
Well hopefully the mark scheme will be fairly leniant, as obviously that is the right answer what you said :dunno: , but I do think they would have said products if there was more two.


The problem with the question is that it's opened ended, so the mark scheme will have to be lenient. If they wanted people use a specific reaction, they would've put "one product" with the "one" in bold. It'd be fairly stupid if they're not going to allow people to gain the mark when they've used the correct chemistry, but failed to identify whether product is pluralised or not.
Reply 781
Avatar for AnniG
AnniG
1
_Andrew_
I thought the paper was horrible :frown:.


There's no doubt about it.. I'm definitely resitting this paper.. I feel like crying though coz I knew this module SO well and just made the most stupid mistakes :frown: like I accidentally said H2SO4(l) hydrolyses an ester/amide bond when obviously it's aqueous.. I think I'm going to cry :frown:
It wasn't a bad paper. It was more than easy to make silly mistake, though. Do you guys think that the grade boundaries will remain the same?
AnniG
There's no doubt about it.. I'm definitely resitting this paper.. I feel like crying though coz I knew this module SO well and just made the most stupid mistakes :frown: like I accidentally said H2SO4(l) hydrolyses an ester/amide bond when obviously it's aqueous.. I think I'm going to cry :frown:

aww :console:

I thought it was pretty good tbh, though i ran out of time and missed a couple of questions =/ The one I feel like crying my eyes iout about is biology i revised for it quite a lot neglecting chemistry but now i will be lucky to even get a C :frown:, and i knew it practically inside out :frown:!
CertifiedAngel
aww :console:

I thought it was pretty good tbh, though i ran out of time and missed a couple of questions =/ The one I feel like crying my eyes iout about is biology i revised for it quite a lot neglecting chemistry but now i will be lucky to even get a C :frown:, and i knew it practically inside out :frown:!


Don't worry, I'm sure you did well. The grade boundaries may very well be lower than the F212 Biology module last year; where you only needed to get about 64-66% for an A.
Thanx :smile:, hopefully!
AnniG
There's no doubt about it.. I'm definitely resitting this paper.. I feel like crying though coz I knew this module SO well and just made the most stupid mistakes :frown: like I accidentally said H2SO4(l) hydrolyses an ester/amide bond when obviously it's aqueous.. I think I'm going to cry :frown:



Im pretty pissed of, I mucked up the spectroscopy question:mad: Like really bad
New Username
ohh what an exam huh guys.
It was fairly easy, but I am disappointed in my self for not doing well. I had very little time to check over answer. I may have made many small errors.

The last question asking what ABC were:
A = Na
B = Na2CO3
C= Br2

it was a wild guess ~ what did you guys get for that?

I put exactly the same, but people are saying potassium dichromate and NaBH4 :s-smilie:
Reply 788
Avatar for Noble.
Noble.
17
student92
I put exactly the same, but people are saying potassium dichromate and NaBH4 :s-smilie:


There's more than one possibility for each of the reactions, it's an open ended question.
Noble.
There's more than one possibility for each of the reactions, it's an open ended question.

So do you think Br2 and NaCO3 will be right? what ester did people get for the spec?
I put :

A- NaOH
B- Ethanol (it had COOH, so could become an ester)
C-Acidified potassium dichromate (to reduce the alcohol to a COOH)

And what was the answer to the question with the repeat unit and to identify the amino acid? was it Leucine?
Reply 791
Avatar for AnniG
AnniG
1
student92
So do you think Br2 and NaCO3 will be right? what ester did people get for the spec?


Methyl 2-methylpropanone if I remember correctly... I'm fairly confident about that one I hope I'm not wrong!
Noble.
The problem with the question is that it's opened ended, so the mark scheme will have to be lenient. If they wanted people use a specific reaction, they would've put "one product" with the "one" in bold. It'd be fairly stupid if they're not going to allow people to gain the mark when they've used the correct chemistry, but failed to identify whether product is pluralised or not.


How would there be 2 products? If you react with say NaOH, for the aspirin, I think it had a COOH on the ring. That wouldn't break it down into 2 things :s-smilie: Wouldn't it just form the Na+ salt of the COOH. And do the same to the other one with the OH bonded to the phenol?

You were not reacting it with NaOH under reflux, with concentreated H2SO4, so for that one anyway, wouldn't it be 1?
Reply 793
Avatar for Noble.
Noble.
17
ViolinGirl
How would there be 2 products? If you react with say NaOH, for the aspirin, I think it had a COOH on the ring. That wouldn't break it down into 2 things :s-smilie: Wouldn't it just form the Na+ salt of the COOH. And do the same to the other one with the OH bonded to the phenol?

You were not reacting it with NaOH under reflux, with concentreated H2SO4, so for that one anyway, wouldn't it be 1?


One had a peptide bond, the other had an ester linkage, I'm talk about hydrolysing both of them.

No, reacting it with NaOH would hydrolyse it into two products, then the Na would react with the carboxylic acid formed to generate the carboxylate.
Weird paper i think. Started off easy and ended up weird. For the NMR I got (CH3)2CHCOOCH3

For the last one I did (no idea if I am right)

A= NaBH4 ( reduces c=o )

B= cold aquous NaOH (gives COONa)

C= ethanoic acid with h2so4 refulx = eaterification
I think I may have got the wrong ester:

CH3-COO-(CH3)2CH ??

What did everyone else get?
Also could not come up with anything for the impurity :|
Reply 796
Avatar for Samhi
Samhi
For the last question i did:

A: NaOH
B: aqueous alkali (think its wrong....)
C: NaBH4 (to reduce ketone into secondary alcohol)

dunno really.....hope at least one is right..
ViolinGirl
I put :

A- NaOH
B- Ethanol (it had COOH, so could become an ester)
C-Acidified potassium dichromate (to reduce the alcohol to a COOH)

And what was the answer to the question with the repeat unit and to identify the amino acid? was it Leucine?

Wasn't it a sequence of amino acids, so like glycine, leucine and isoleucine... i can't hardly remember what I put down, well it was something like that :s-smilie:
student92
Wasn't it a sequence of amino acids, so like glycine, leucine and isoleucine... i can't hardly remember what I put down, well it was something like that :s-smilie:


It was a chain, of one repeating amino acid and you had to identify it, I was out of time, so put leucine.

:s-smilie:

What people are saying on here has got me worried about the last question now....I hope you did only have to draw 1 product!
I've failed so bad, it's a retake for sure.

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