Don't forget -COOH(Original post by annaj97)
Why do only O-H and N-H peaks disappear when you add D2O?
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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch
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Sarcastic Goats
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itsConnor_
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(Original post by Magicalgeofray)
D2O Undergoes Proton exchange with the Hydrogen atoms (protons). D atoms have an even number of nucleons so are undetected in the NMR spectra and results in no O-H or N-H peaks -
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- 13-06-2016 21:07
(Original post by CalistaJupiter)
They don't all protonate… I did a past paper that had a 'zwitterion' with an extra cooh side group and the mark scheme said "reject if both cooh groups are shown to have donated a proton" because only groups directly involved in being an amino acid (eg RCH(NH2)COOH) actually protonateCOOH stay COOH
pH above IP, all COOH beccome COO- and NH2 stay NH2 -
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- 13-06-2016 21:08
(Original post by annaj97)
Why does this only happen with O-H and N-H peaks? -
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- 13-06-2016 21:08
(Original post by Rust Cohle)
Ooops, number 4 was typo; should be suggest why organic product in q3 cannot be hydrolyses.
1, 2 and 3 three correct. -
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- 13-06-2016 21:11
(Original post by annaj97)
Why does this only happen with O-H and N-H peaks? -
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- 13-06-2016 21:12
(Original post by tcameron)
the isolectric point is when it exists as a zwitterion, not below the isoelectric point -
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- 13-06-2016 21:12
But carboxylic acid can still go through reduction if added 2[H] e.g. Ethanoic acid to Ethanol
Last edited by sakuraton; 13-06-2016 at 21:17. -
Magicalgeofray
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- 13-06-2016 21:13
If anyone has ran out of Past papers i would recommend AQA Unit 4 papers from about half way onwards is very similar to our spec, however the questions deal with concepts our spec has not covered, yet we can apply our knowledge to questions such as reaction mechanisms, personally these were great for practicing those kinda awkward application based questions.
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- 13-06-2016 21:14
(Original post by sakuraton)
But carboxylic acid can still go through reduction if added 2[H] e.g. Methanoic acid to Methanol -
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- 13-06-2016 21:14
(Original post by Magicalgeofray)
Attachment 549315Attachment 549307 This is what the mark scheme says on Zwitter ions for this question i was confused too so emailed my teacher, and this was her reply but I am still confused:
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Break at the peptide linkage -
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- 13-06-2016 21:15
(Original post by tcameron)
because methanol is effectively an aldehyde -
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- 13-06-2016 21:16
(Original post by tcameron)
because methanol is effectively an aldehyde -
lai812matthew
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- 13-06-2016 21:16
https://en.wikipedia.org/wiki/Zwitterion
In chemistry, a zwitterion is a neutral molecule with both a positive and a negative electrical charge. Multiple positive and negative charges can be present. Zwitterions are distinct from dipoles, at different locations within that molecule.
if there is a molecule with n amines and n carboxyls, wouldn't it be all protonated as long as the charge stays netural? (n-n=0) -
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- 13-06-2016 21:18
(Original post by sakuraton)
Whoops wrong example, ethanoic acid to ethanol
And I don't think that reaction is possible -
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- 13-06-2016 21:21
(Original post by lai812matthew)
https://en.wikipedia.org/wiki/Zwitterion
In chemistry, a zwitterion is a neutral molecule with both a positive and a negative electrical charge. Multiple positive and negative charges can be present. Zwitterions are distinct from dipoles, at different locations within that molecule.
if there is a molecule with n amines and n carboxyls, wouldn't it be all protonated as long as the charge stays netural? (n-n=0)
But if its put in acid/alkaline respectively, all COOH/NH3 react accordingly if that makes sense? -
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- 13-06-2016 21:22
(Original post by tcameron)
I even meant to say methanioic acid is an aldehyde not methanol
And I don't think that reaction is possible
http://www.ocr.org.uk/Images/79471-q...d-analysis.pdf
http://www.ocr.org.uk/Images/61007-m...is-january.pdf
January 2012, Question 3)b) Thank you! -
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- 13-06-2016 21:22
does anyone have a copy of 2015 papers for F324??
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- 13-06-2016 21:23
(Original post by sakuraton)
Then can you explain this:
http://www.ocr.org.uk/Images/79471-q...d-analysis.pdf
http://www.ocr.org.uk/Images/61007-m...is-january.pdf
January 2012, Question 3)b) Thank you!
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