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OCR A-level Chemistry A Paper 2 - 16th June 2025 [Exam Chat]

Reply 840

4

Original post

by Unrei

Ah that doesn’t work because if they both contained the same amino acid then the solvent wouldnt contain two different amino acids

Yh gg bro it's ov ✌️

Reply 841

xitz_jessix

12

Original post

by Jennifer2314

hey guys, i dont know if this was discussed already so sorry for bringing it up if it was discussed. The question where we had to find the Rf value and draw amino acid where we meant to

•

draw the two amino acids with the R group we found

•

Or draw liek a peptide bond reaction with the r grouop it self

If it is was the second option can someone expalin how they came to that conclusion bc im pretty sure it asked to draw an amino acid so i just did that

You had to draw compound S which was made of the two amino acids you found
1st structure - Amino acid 1 on the left and Amino acid 2 on the right
2nd structure - Amino acid 2 on the left and Amino acid 1 on the right

Reply 842

wompwomp2

6

what mark do you think it would be for a b

Reply 843

Skye123eliz

4

Does anyone remember if there was an mcq on born harber cycles in paper 1? And if so what was it?

Reply 844

Thisiswhy1

8

Original post

by Masrooler

Where would you add the continuation bonds tho? Did U remove the OH and the H on the amide like a normal polyamide?

Yeah I did because my brain defaulted to a polypeptide which you would do that so, yeah I messed up LOL If it was a polypeptide I would be right (amazing cope)

Reply 845

Thisiswhy1

8

Original post

by Skye123eliz

Does anyone remember if there was an mcq on born harber cycles in paper 1? And if so what was it?

Also yes it was like "why is the second electron affinity positive"

Reply 846

ahsbsdfhkasd

8

Original post

by xitz_jessix

You had to draw compound S which was made of the two amino acids you found
1st structure - Amino acid 1 on the left and Amino acid 2 on the right
2nd structure - Amino acid 2 on the left and Amino acid 1 on the right

Isn't there variation to that question? Ie a number of different structures that could be accepted

Reply 847

Tk2007

7

Can anyone remember on the rf table was there a value of like 0.6 somthing cos I got that for my rf I hope I chose the 0.78 one everyone else chose I remember the r group I chose was long —- also for the synthesis 6 marker if I put conditions NaOHand H2S04🥹how much would I be capped by

(edited 10 months ago)

Reply 848

Tk2007

7

Original post

by Tk2007

Can anyone remember on the rf table was there a value of like 0.6 somthing cos I got that for my rf I hope I chose the 0.78 one everyone else chose I remember the r group I chose was long —- also for the synthesis 6 marker if I put conditions NaOHand H2S04🥹how much would I be capped by

Also for the alc into haloalkane I set I put aqueaous NaBr - I haven’t seen any mark schemes on that specifically so idk if they would award me th mark ☹️

Reply 849

ellieprety101

1

what was that ester bond q about qhy it can be hydrolysed or smth

Reply 850

Tk2007

7

Original post

by ellieprety101

what was that ester bond q about qhy it can be hydrolysed or smth

Yh 1 mark on calculating rf 2 marks on the 2 diff structure of compound S

Reply 851

Unrei

10

Original post

by Tk2007

Also for the alc into haloalkane I set I put aqueaous NaBr - I haven’t seen any mark schemes on that specifically so idk if they would award me th mark ☹️

Nah it wouldnt unfortunately, you have to mention H2SO4 as well but that’s only one mark so don’t worry about it

Reply 852

Anonymous2246

12

could someone post the unoffcicial mark scheme for both papers 1 and 2 if there is one please? tsym

Reply 853

Tk2007

7

Original post

by Unrei

Nah it wouldnt unfortunately, you have to mention H2SO4 as well but that’s only one mark so don’t worry about it

No i did but its not i put NaOH aq H2S04 but just regular NaOH😔

Reply 854

miastokes2007!

2

Original post

by Tk2007

No i did but its not i put NaOH aq H2S04 but just regular NaOH😔

Ngl I really doubt it would matter if you put aq

Reply 855

Skye123eliz

4

For the structure of the ester in the nmr- was the structure (ch3)2chcooch2ch3 or ch3ch2cooch(ch3)2 Or would it not matter?

Reply 856

unwritten-carpor

1

Original post

by Skye123eliz

For the structure of the ester in the nmr- was the structure (ch3)2chcooch2ch3 or ch3ch2cooch(ch3)2 Or would it not matter?

its CH3CH2COOCH(CH3)2 as this gets the large 71 m/z peak. however on the mark scheme top band will probably be (ch3)2chcooch2ch3 or ch3ch2cooch(ch3)2 (as this is what usually happens with esters) and to get the full marks u need to notice the 71m/z

Reply 857

Unrei

10

Original post

by unwritten-carpor

its CH3CH2COOCH(CH3)2 as this gets the large 71 m/z peak. however on the mark scheme top band will probably be (ch3)2chcooch2ch3 or ch3ch2cooch(ch3)2 (as this is what usually happens with esters) and to get the full marks u need to notice the 71m/z

You do not need to notice a certain peak. You just need to state what a peak could be and state what the relevant fragment ion is. There is normally like a variety of peaks you could talk about in the mark scheme. I think i mentioned two the obvious one being the RFM of the molecule and the peak are 43 m/z i think.

Reply 858

Skye123eliz

4

Original post

by unwritten-carpor

its CH3CH2COOCH(CH3)2 as this gets the large 71 m/z peak. however on the mark scheme top band will probably be (ch3)2chcooch2ch3 or ch3ch2cooch(ch3)2 (as this is what usually happens with esters) and to get the full marks u need to notice the 71m/z

How does ch3ch2cooch(ch3)2 get a 71 mz peak? Becuase I got that and I couldn’t get 71 mz for it at all?