OCR A Chemistry F324 Rings, Polymers and Analysis Thu 26 Jan 2012

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Reply 1000

rogersnm

Original post by VQG

Wasn't the peak with integration 9 a singlet?

Yeah it was, the structure is CH3-CH2-O-CO-CH2-C(CH3)3

Reply 1001

Yarpie

Original post by wig44

I don't know why people think boundaries will be high. Irrespective of whether or not you found this paper hard, it was harder than previous papers and the format felt 'different'. I'm sure boundaries will not be higher than previous years and wouldn't be surprised if they were lower. My chemistry teacher agreed with the class that it was not an easy paper compared to previous papers of this spec.

The last 10 marker was a joke though, it really should have been more difficult.

I agree. The format would throw a lot of people off. I'm pretty sure a lot of people wouldn't have recognized the movement of the electrons in the mechanism going from S to the O from the double bond which I have definitely never seen before but managed to deduce it. There were a lot of stretch and challenge questions which makes me thing grade boundaries will be lower than the usual 44-46 for an A.

Reply 1002

Patchey1000

Original post by Dreamweaver

Decent paper - expecting slightly lower than usual grade boundaries. Lost 1 mark on the first question and 2 marks on the synthesis question. How did everyone else find it?

Ester was (CH3)3CH2COOCH2CH3

thats wrong how could you have 3 carbons and 2 hydrogens on one carbon

Reply 1003

lukas1051

I know it's a really silly thing but does it matter if you draw the ester the wrong way round?

I put (CH3)CCH2OOCCH2CH3

ie. instead of writing it the conventional way RCOOR I wrote ROOCR. Will it matter?

Reply 1004

StrawberryKoi

Original post by Yarpie

Uh... yes it does matter? That's the point of phenol and the alternating delta negative and delta positive carbons. It only reacts on the delta positive carbons which are at 2,4 and 6.

Carbon 4 was already reacted so you had to draw Bromine on carbon 2 and 6.

You're right about that but in a previous year's paper, they had a similar question and you get the mark as long as you've added one or more bromine anywhere on the ring

Reply 1005

rogersnm

Original post by lukas1051

I did a similar sort of thing but put ROCOR, hopefully it won't matter :colondollar:

Reply 1006

fudgesundae

Original post by lukas1051

That is wrong anyway. The 3 methyl groups were on the carboxylic acid side.

It was:

(CH3)3CCH2COOCH2CH3

Reply 1007

Kir4nK

FGS someone plz confirm the structure of the ester ... ??

Reply 1008

proxy

Original post by thmshrpr

I'm not sure if it was just me, or whether i was seeing things, but in the last ester question there was a mistake. Not a huge one but it could have thrown people. It said that the ester was a Butan-1-ol? or something similar. And then went on to name the alcohol again. The structure definitely wasn't an ester, and i just wondered if anyone else noticed it aswell? Or if my eyes were just playing tricks on me :P

yeah it was wrong, confused me for a second!

Reply 1009

lukas1051

Original post by rogersnm

I did a similar sort of thing but put ROCOR, hopefully it won't matter :colondollar:

Haha... that's why I HATE structural formula!

Reply 1010

Phenylethylamine_

I think this will help regarding the paracetamol qs, a similar question in Jan 2010 paper:
mark scheme:

Reply 1011

Dreamweaver

Original post by Patchey1000

thats wrong how could you have 3 carbons and 2 hydrogens on one carbon

Original post by VQG

Wasn't the peak with integration 9 a singlet?

Forgot to add the C next to the (CH3)3

Reply 1012

lukas1051

Original post by fudgesundae

That is wrong anyway. The 3 methyl groups were on the carboxylic acid side.

It was:

(CH3)3CCH2COOCH2CH3

Ah FFS... how could you tell, was it from the shift values? God, I need to stop thinking about this question and move on.

Reply 1013

fudgesundae

THE ESTER WAS:

ethyl-3,3-dimethylbutanoate

google it and you will see it

Reply 1014

fudgesundae

Original post by lukas1051

Ah FFS... how could you tell, was it from the shift values? God, I need to stop thinking about this question and move on.

yeh the quartet was in a position which had a shift relating to a C-O bond. So it must have been on the alcohol side.

Reply 1015

faz_341

guys isolectric point: where there is no overall charge across the amino acid?

Reply 1016

heeeello

how were we meant to know by how much to reduce/oxidise stuff to as it didnt say whether they distilled off immediately or refluxed it!! i just went all the way

Reply 1017

fudgesundae

Original post by faz_341

guys isolectric point: where there is no overall charge across the amino acid?

yes:

ph 3 was COOH
pH 10 was NH2

Reply 1018

Yarpie

Original post by lukas1051

Don't think so... It's basically just flipped the molecule as the double bond has to be on the second oxygen and not the first going from left to right as you've drawn it.