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

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Reply 660
Original post by ForeverDay
Just out of interest what would be the mechanism for this reaction? I can see the products formed and that makes sense but I don't entirely understand how they got there.


I just googled it and apparently it's called the Cannizzaro reaction? There's a mechanism on the wikipedia page
https://en.wikipedia.org/wiki/Cannizzaro_reaction

Original post by pineneedles
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In the original question, the only reactant (besides benzaldehyde) was KOH, so there weren't any other oxidising/reducing agents!
Original post by kawehi
I just googled it and apparently it's called the Cannizzaro reaction? There's a mechanism on the wikipedia page
https://en.wikipedia.org/wiki/Cannizzaro_reaction



In the original question, the only reactant (besides benzaldehyde) was KOH, so there weren't any other oxidising/reducing agents!


Thanks, I did try google it but I couldn't find it so that was v helpful.
Original post by ForeverDay
Just out of interest what would be the mechanism for this reaction? I can see the products formed and that makes sense but I don't entirely understand how they got there.


Definitely wouldn't worry about mechanisms for something like that, it'd probably be something incredibly complex anyway but for those 'suggest' kind of questions I think you're just supposed to apply your knowledge to something you haven't seen/don't explicitly know to answer it without understanding what's going on :tongue:
Original post by kawehi
I just googled it and apparently it's called the Cannizzaro reaction? There's a mechanism on the wikipedia page
https://en.wikipedia.org/wiki/Cannizzaro_reaction



In the original question, the only reactant (besides benzaldehyde) was KOH, so there weren't any other oxidising/reducing agents!


That's pretty cool actually, not too complicated either haha
Original post by megafidget
Definitely wouldn't worry about mechanisms for something like that, it'd probably be something incredibly complex anyway but for those 'suggest' kind of questions I think you're just supposed to apply your knowledge to something you haven't seen/don't explicitly know to answer it without understanding what's going on :tongue:


Haha, I know but I like trying to understand it anyway. Also, I generally find it helpful just to try see as much as possible for those suggest questions (I don't know how much it helps but it makes me feel better lol).
Original post by ForeverDay
Haha, I know but I like trying to understand it anyway. Also, I generally find it helpful just to try see as much as possible for those suggest questions (I don't know how much it helps but it makes me feel better lol).


That's probably for the best tbh! At least you'll be less likely to be surprised in the exam and it's a good feeling if you can understand it well :smile:
Original post by Serine Soul
Just to check, what's the answer?

And yeah you would


60 percent

I will confirm

thanks.
Original post by Serine Soul
Besides some reactions, mass spec and IR, how much of AS are we expected to remember? I'm going to read over my AS notes today


My teacher advised us to still know all the AS mechanisms for synthesis topics
Also avogadros constant - i've seen that as an A2 question before
guys, the proton on the aldehyde group produces a singlet right?? because its being "shielded" by the O??
Original post by RayMasterio
guys, the proton on the aldehyde group produces a singlet right?? because its being "shielded" by the O??


I don't think that is correct.

is the nitration of phenol the same as the nitration of benzene?
Original post by L'Evil Wolf
is the nitration of phenol the same as the nitration of benzene?




From chemguide:

The -OH group attached to the benzene ring in phenol has the effect of making the ring much more reactive than it would otherwise be.For example, as you will find below, phenol will react with a solution of bromine in water (bromine water) in the cold and in the absence of any catalyst. It also reacts with dilute nitric acid, whereas benzene itself needs a nitrating mixture of concentrated nitric acid and concentrated sulphuric acid.
so when is the proton shielded????
Reply 673
Original post by L'Evil Wolf
is the nitration of phenol the same as the nitration of benzene?


i think so, maybe with phenol u dont need to h2so4 as a catalyst since phenol has a higher electron density so could polarise hno3 on its own


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Original post by EricPiphany


From chemguide:


Original post by ranz
i think so, maybe with phenol u dont need to h2so4 as a catalyst since phenol has a higher electron density so could polarise hno3 on its own


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percentage yield was 40 percent from before.

Thanks for the info guys makes sense. Saw an eight marker from one of the legacy paperpse onn this!
Hey guys, hope everyones grinding out revision.

Could someone please explain this question to me:


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Can someone please explain if hydrogen bonds form between C=O groups, or just -OH groups?
And also, if I have -COOH group, is the proton attached to the oxygen a singlet? Because it's not directly attached to the carbon, so won't be split?
Reply 677
guys what do they mean with "in the proton NMR spectrum, the peak at xxx would normally be expected at a chemical shift value about 1ppm to the right"


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Reply 678
Original post by zirak46
Hey guys, hope everyones grinding out revision.

Could someone please explain this question to me:


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is this a legacy paper?


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Original post by zirak46
Hey guys, hope everyones grinding out revision.

Could someone please explain this question to me:


Posted from TSR Mobile


Legacy paper right? Probably want the answer in terms of of wavelengths and stuff that isn't on the spec anymore.

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