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OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

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Reply 1460
Avatar for S.G.
S.G.
22
Original post by medicapplicant
I just had a look at the test today it didn't say anything about cation being secondary


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So what is the correct answer
Original post by medicapplicant
I just had a look at the test today it didn't say anything about cation being secondary


Posted from TSR Mobile


check it again on the depth paper under the mass spec it said the fragment with the highest abundance(43) is a secondary carbocation
Original post by Magneticbreach
check it again on the depth paper under the mass spec it said the fragment with the highest abundance(43) is a secondary carbocation


I'll have a look at it again tomorrow but I'm pretty sure it just said cation not secondary but I'll have a look, either way can't change the answer now.


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Original post by medicapplicant
I'll have a look at it again tomorrow but I'm pretty sure it just said cation not secondary but I'll have a look, either way can't change the answer now.


Posted from TSR Mobile


Yeah I'm fairly certain it said secondary carbocation, I remember thinking about it having 2 alkyl groups attached so it was probably straight instead of branched.
Original post by medicapplicant
I'll have a look at it again tomorrow but I'm pretty sure it just said cation not secondary but I'll have a look, either way can't change the answer now.


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yeah theres no pint worrying now:smile:
(edited 7 years ago)
is there an unnoficial mark scheme anywhere
Why are people saying it was 2-methylpropanoic acid instead of butanoic acid?
Original post by h3rmit
Why are people saying it was 2-methylpropanoic acid instead of butanoic acid?


Something to do with the statement at the bottom of the page, the peak with the highest abundance was caused by a secondary carbocation. Honestly I don't understand the significance but the only reason i think they would put that in is that there would be more than 1 possibility, so its either one or the other. I wrote butanoic myself
Original post by Magneticbreach
check it again on the depth paper under the mass spec it said the fragment with the highest abundance(43) is a secondary carbocation


http://webbook.nist.gov/cgi/inchi?ID=C107926&Mask=200

http://webbook.nist.gov/cgi/cbook.cgi?ID=C79312&Mask=200

It's worrying how many chemistry teachers out there allegedly think the answer is butanoic acid. Look at the mass spectra in the links.
(edited 7 years ago)
Original post by Jitesh
Print off an IR spectroscopy graph of butanoic acid and 2-methylpropanoic acid and you should see the fingerprint region is more like 2-methylpropanoic acid



http://webbook.nist.gov/cgi/cbook.cgi?ID=C79312&Type=IR-SPEC&Index=2

http://webbook.nist.gov/cgi/cbook.cgi?ID=C107926&Units=CAL&Type=IR-SPEC

I agree.
Original post by TeachChemistry
http://webbook.nist.gov/cgi/inchi?ID=C107926&Mask=200

http://webbook.nist.gov/cgi/cbook.cgi?ID=C79312&Mask=200

It's worrying how many chemistry teachers out there allegedly think the answer is butanoic acid. Look at the mass spectra in the links.


yeah i know
Original post by TeachChemistry
http://webbook.nist.gov/cgi/inchi?ID=C107926&Mask=200

http://webbook.nist.gov/cgi/cbook.cgi?ID=C79312&Mask=200

It's worrying how many chemistry teachers out there allegedly think the answer is butanoic acid. Look at the mass spectra in the links.


Hooray, your first comment on this thread that was actually helpful
Original post by asinghj
Hooray, your first comment on this thread that was actually helpful


Funny.
Original post by TeachChemistry
Funny.


so 4/6 marks for butanoic acid even if I used 89 instead of 88? or less do you think?
Original post by TeachChemistry
Funny.


😂😂
Original post by ronnydandam
so 4/6 marks for butanoic acid even if I used 89 instead of 88? or less do you think?


Without a markscheme I have no idea. All I could say with certainty is it's not 6.

Just so you know for the future - any compound comprising C, H and O will ALWAYS have an even numbered MW so the M+ ion is even.
Original post by TeachChemistry
Without a markscheme I have no idea. All I could say with certainty is it's not 6.

Just so you know for the future - any compound comprising C, H and O will ALWAYS have an even numbered MW so the M+ ion is even.


Yeah I know, hopefully not less than 3. And yes thanks a lot , wil keep that in mind next time!
Original post by asinghj
😂😂


Feel free to make your first positive contribution whenever you are ready.
Original post by TeachChemistry
Feel free to make your first positive contribution whenever you are ready.


😂😂 I already have mate, BEFORE the exam I was helping on here😂😂
Reply 1479
Avatar for MrDogg
MrDogg
What does everyone predict for grade boundaries?

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