The Student Room Group

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

Scroll to see replies

Original post by thad33
To be honest I don't find the legacy papers that much of a help. Not in pushing the difficulty anyway.

Although they're good for repetition.


Posted from TSR Mobile


Totally agree
Ive done the first four past papers of f325 and first 3 papers of unifying concepts and trends&patterns each.

The actual f325 ones obviously helped massively but the legacy ones arent that helpful. How many of you done of f325 and legacy? And what are you doing now? :smile:
Posted from TSR Mobile
Reply 581
Original post by zirak46
Woah that aggression.
Which questions do you suggest? From past papers? Theres only 8 and I dont want to use all of them up so soon. I need some for the days before the exam

Posted from TSR Mobile


How exactly was that aggressive? Calm down dear.

There are more resources than just past papers.
Original post by alow
How exactly was that aggressive? Calm down dear.

There are more resources than just past papers.


please link sir
Is this off-topic?

download.jpg
Original post by rory58824
Is this off-topic?

download.jpg


No mate, it was perfect


Posted from TSR Mobile
Original post by thad33
No mate, it was perfect


Posted from TSR Mobile


Brilliant, maybe the cat can give us hope for the exams :smile:
Can anyone tell me exactly what they mean by this part of the spec:

"Compare the Kekulé and delocalised model of benzene in terms of p-orbital overlap forming pi bonds"

I know for delocalised model you would say: Sideways overlap of the p-orbital produces a delocalised pi-electron ring above and below the plane. But what about Kekulé's, how would you word that?
Original post by RayMasterio
<a href="http://tinypic.com?ref=mcbrtj" target="_blank"><img src="http://i65.tinypic.com/mcbrtj.png" border="0" alt="Image and video hosting by TinyPic"></a>

can someone please tell me why the reduction process is wrong? Is a reduction of a COOH always OH? Or is it because we are polymerising so it must be COOH + OH to form the peptide link?


You cannot reduce carboxylic acid with NaBH4 as it is not strong enough, LiAlH4 is used , and it is a different mechanism (which is not on ocr spec), therefore mechanism you have drawn is not correct and you should just remember if they ask to reduce carboxylic acid it turns into a primary alcohol
Reply 588
image.jpg

Can someone explain this? This molecule only has 4 hydrogen environment but 5 peaks??

You cannot see the splitting pattern on the sheet so I've written up the splitting next to the peak :smile:
Guys, in NMR questions when they say ''this proton was initially expected at x ppm but is at y ppm instead'' which chemical shift should we analyse? ;S
Original post by AqsaMx
image.jpg

Can someone explain this? This molecule only has 4 hydrogen environment but 5 peaks??

You cannot see the splitting pattern on the sheet so I've written up the splitting next to the peak :smile:


Are you sure you have the correct molecule?
Original post by AndrewC19
Can anyone tell me exactly what they mean by this part of the spec:

"Compare the Kekulé and delocalised model of benzene in terms of p-orbital overlap forming pi bonds"

I know for delocalised model you would say: Sideways overlap of the p-orbital produces a delocalised pi-electron ring above and below the plane. But what about Kekulé's, how would you word that?


Kekulé's model consists of p-orbitals that overlap between 2 carbons, meaning that the electrons are 'localised' between 2 carbons and not delocalised in the ring.
Original post by alow
How exactly was that aggressive? Calm down dear.

There are more resources than just past papers.


Just kidding pal!

Set me these resources tho
Original post by rory58824
Is this off-topic?

download.jpg


I got my ION you
*slaps knee*
ok i'll leave..
Reply 594
Original post by RetroSpectro
Are you sure you have the correct molecule?


image.jpeg
Original post by AqsaMx
image.jpeg


Not sure how thats possible, there must be an error some where, whether it be with the question or your interpretation :dontknow:
Original post by Heisenberg___
Came across this fantastic link for old chemistry past papers. The person who made this has also kindly highlighted questions that we can skip (as they aren't relevant to our spec). Enjoy!

http://www.chemhume.co.uk/A2CHEM/ExamsMSA2/ExamMSA2%20additional.htm


This is great! Thanks! :biggrin:
Original post by ToLiveInADream
Guys, in NMR questions when they say ''this proton was initially expected at x ppm but is at y ppm instead'' which chemical shift should we analyse? ;S


The chemical shift at x ppm. I think they do this so that the peaks don't overlap, making it hard to analyse :smile:
Original post by Kamara7
The chemical shift at x ppm. I think they do this so that the peaks don't overlap, making it hard to analyse :smile:


Ahh that makes sense! I'll practise some of these questions now, thanks :biggrin:
Guys, another question:

I don't understand the initiative behind these kind of mechanisms - which is probably why I get them wrong. I would be grateful if someone could explain intuitively what's happening.

Why does the electron pair move to the Carbon atom, from the oxygen? Why not from the o-c bond to the oxygen atom that is removed?

Quick Reply

Latest