The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

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

Scroll to see replies

Reply 2000
Avatar for Taona
Taona
Original post by faglad202
I wrote the one with 2 double bonds purely becuase it leads to more trans structures?


Surely if the structure had one trans configuration and the other was cis then it wouldn't pack closely together?? so out of four combinations(cis,cis)(cis,trans)(trans,cis)(trans,trans) only one (trans,trans) would be really bad? Im not really sure though i kept self doubting loads with that question.
Original post by cr7alwayz
For the first step of the incomplete mechanism question (2 marks),

I just put positive dipole on the carbon and negative dipole on the oxygen.
And a curly arrow going from the double bond to the oxygen.

Did we have to draw the OH- attacking the carbon with a curly arrow as well?


yes, cus OH is in the product
Original post by popo111
Can someone confirm, is the first answer saturated fat or the other unsaturated ones??


Saturated is bad for you 95% sure


Posted from TSR Mobile
What do people think the boundaries will be for a grade C?
Also can anyone explain how they worked out the percentage yield question?
Did anyone find this exam hard?

I thought it was a nice paper but made a few silly mistakes :/
What did everyone get for the splitting patterns of the compound after D20 had been added?I got two doublets and one singlet.
Original post by anndz3007
yeah you not include it but it still affect the chemical shift no ??


I doubt it.
Original post by Ula456
Did anyone find this exam hard?

I thought it was a nice paper but made a few silly mistakes :/
What did everyone get for the splitting patterns of the compound after D20 had been added?I got two doublets and one singlet.


2 doublets and a sextuplet iirc


Posted from TSR Mobile
Original post by JennyMoorcroft
My friend wrote his structures in pencil, will the pencil pick up for marking?


Yes i got a copy of my f322 back and i had drawn in pencil and you could see it on the scanned image, i also did all mine in pencil so i really hope so
what might the grade boundaries be?
using exact numbers isn't the % yield 2.67 not 2.66!!!???! To 3sf
Original post by cr7alwayz
For the first step of the incomplete mechanism question (2 marks),

I just put positive dipole on the carbon and negative dipole on the oxygen.
And a curly arrow going from the double bond to the oxygen.

Did we have to draw the OH- attacking the carbon with a curly arrow as well?


You had to:

-draw a positive dipole on the carbon in the carbonyl group, negative dipole on the attatched oxygen
-a curly arrow going from either the negative charge OR the lone pair on the OH- ion to the carbon
-and lastly you needed to draw an arrow from the C=O bond to the oxygen
Just our luck eh!

Nah real talk, just looking at these posts, many ppl made mistakes, so we'll have to see...

Hopefully, F325 will benefit us!
Original post by Spwoosh
It wouldn't be branched at all, everybody just got a little over excited and over complicated it. It's literally ch3ch2ch2ch(oh)ch3. CNMR peaks are the distance of the carbons from the electronegative point. The Ch2 next to the Ch(oh) will have the same peak as the Ch3 on the other end of the Ch(oh) so there are only 4 peaks. We were right. The answer most people got was wrong because if you look at it carefully you'd see it only has 3 peaks.


nah it has to be branched for the 13C nmr to only have 4 environments, in ch3coch2(ch3)2 the last 2 methyls have the same environment
Original post by Ula456
Did anyone find this exam hard?

I thought it was a nice paper but made a few silly mistakes :/
What did everyone get for the splitting patterns of the compound after D20 had been added?I got two doublets and one singlet.


It was two doublets and one Sextet (a multiplet would have sufficed)
Original post by GawdHeresEmmie
The invigilators always say 'pencils may be used for drawings and rough notes' so I should assume so! (i go over mine in pen afterwards though bc I worry)



I don't think thats right? (CH3)2CHCH(OH)CH3 would give 4, not 3 peaks, as the two methyl groups are in identical environments.


Yes, the 2 methyl groups would give 1 peak but the CH2 next to the CH(0h) and the CH3 on the other side will both ALSO give only 1 peak since they are both right next to the carbon with the oxygen. That just leaves the CH(oh) by itself which would make the third and final peak. Sat down with about 10 of my mates after this exam to talk it through and we all decided the straight chain was the only possible answer.
Original post by anndz3007
where do you put the charge on A ?? i thought nothing break down so i just leave it neutral ??

My diester was a cyclic compound do you think that would be acceptable
Original post by President J
I doubt it.


check the book page 95, the 2 NMR with and without D2O, the only thing that changed is the presence of the O peak
Original post by maisym00
Oh god, I wrote about them being photobiodegradavle on exposure to UV😕 Oops


I mentioned that also, because it asked how it could be broken down AND how it dissolves
Original post by anndz3007
where do you put the charge on A ?? i thought nothing break down so i just leave it neutral ??


It's called "Molecular ion peak" and i remembered my teacher banging on about + charge so I just put the whole molecule and that whole thing has + charge
For the difference between chemical synthesis and fermentation of sugars I think I wrote that fermentation of sugars uses renewable resources or something like that.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you