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OCR A 2016 Chemistry A* A-Level Resources

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Original post by UnknownAnon
Isn't it because a cis-trans sterioisomer has the same structural formula but different arrangements of atom in space. So they produce the same product (the only difference being the arrangement of Br in space to form cis and trans)

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Hey thanks for the response, idk i'm pretty confused tbh the answer is:

(the product is saturated hence) there is no restricted rotation/singlebonds allow rotation/because C=C prevents rotation

I don't get it :frown:
Also for question d(ii) on page 144, why cant one of the isomers be something like 2,5-dimethylpentane, 1,5-dimethylpentane, 1,4-dimethylpentane, 1,3-dimethylpentane, 1-methylhexane, etc ... ?
Original post by dpoojaraa
I don't understand how the 2H on the phenol ring, each side of the aldehyde are equal to 1? Surely that's 2 environments? Please can you elaborate how it's 1?



Oh wait, you're right! Apologies. Hmm... then there should be 6 environments in total, no? Unless you count the H on each of the carbons next to the ester and alcohol as one environment... but that's probably not correct either as you can't have rotation around a double bond
Original post by chanda01
I've just realised that the protons on the carbons next to the aldehyde can't count as one as it's not symmetrical... are you sure there's only 5 proton environments? hmm...


There are proton environments on the -COOH, -OH and -OCH3 group, and three of the hydrogens on benzene have been substituted so there are 3 environments on the ring itself

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Original post by tvdfan
Hey thanks for the response, idk i'm pretty confused tbh the answer is:

(the product is saturated hence) there is no restricted rotation/singlebonds allow rotation/because C=C prevents rotation

I don't get it :frown:


I think it's because it becomes saturated and you can't have a cis trans isomer that's saturated so they become exactly the same?
Original post by xsashax
I think it's because it becomes saturated and you can't have a cis trans isomer that's saturated so they become exactly the same?


I think this is a good point to reiterate that when you find questions you really struggle with, everyone else struggles too! This is especially useful in exams, knowing that a question is tough, for example, last year when I was in F324 I was smiling while doing the DNP question, because I knew most people wouldn't have a clue.

Always remember it's a competition and you're just trying to get one of the top scores relative to other students :P
These are so good, thank you for taking the time to do this!
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Ss0
image.jpgI need help on this acid hydrolysis. The markscheme says it produces a compound with NH2+ but isnt it a NH3+ salt?? :frown:
Original post by BrownGuyIrfan
These are so good, thank you for taking the time to do this!


No problem man! It helps me revise content and I'm motivated knowing it'll help others in the future :smile:
Original post by Ss0
image.jpgI need help on this acid hydrolysis. The markscheme says it produces a compound with NH2+ but isnt it a NH3+ salt?? :frown:


No look at how many bonds are already attached to the nitrogen :smile:
Hi,
I was wondering what university and course you went onto after your results? You had really impressive btw.
Hi, I was wondering if you have any general tips for Chemistry and Maths? (Your notes are awesome by the way! Thank you so much!!!)

Also, when did you begin your revision and for how long daily?
Original post by Christauf
Hi,
I was wondering what university and course you went onto after your results? You had really impressive btw.


Hey there! I went to study Chemical Engineering at the University of Manchester :-)
Hi, I also want to do chemical engineering. What are your thoughts on Manchester and the course itself?
Original post by chanda01
Hi, I was wondering if you have any general tips for Chemistry and Maths? (Your notes are awesome by the way! Thank you so much!!!)

Also, when did you begin your revision and for how long daily?


Maths is totally practice. Practice enough you'll get 100%. Chemistry has more application but is similar in that practice develops your solving skills.
will anyone do me a favour? I'm going OCR a salters but I've got the revision guide for OCR b and done most of my notes from there:frown: so if anyone has the cgp revision guide and would kindly give me the code for the online edition? Please
(edited 8 years ago)
Original post by Beccajane1026
will anyone do me a favour? I'm going OCR a salters but I've got the revision guide for OCR b and done most of my notes from there:frown: so if anyone has the cgp revision guide and would kindly give me the code for the online edition? Please


OCR B is the salters one A is the non-slater one which guide do you need. I find your question slightly confusing.


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Original post by Beccajane1026
will anyone do me a favour? I'm going OCR a salters but I've got the revision guide for OCR b and done most of my notes from there:frown: so if anyone has the cgp revision guide and would kindly give me the code for the online edition? Please


I've got the revision guide but I'm not sure where you find the code in it?

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I'm a bit confused by the polyesters and polyamides bit on the spec where it says 'Candidates for will not be expected to recall the structures of synthetic polyesters and polyamides or their monomers'
Does this mean we don't have to know how to draw out or know the systematic names of terylene, PLA, nylon-6,6 or kevlar? That probably sounds like a stupid question but I'm just not sure what we actually need to know because it only says we have to 'describe condensation polymerisation to form' and then lists them so it's pretty vague

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(edited 8 years ago)
Original post by LThomas694
I'm a bit confused by the polyesters and polyamides bit on the spec where it says 'Candidates for will not be expected to recall the structures of synthetic polyesters and polyamides or their monomers'
Does this mean we don't have to know how to draw out or know the systematic names of terylene, PLA, nylon-6,6 or kevlar? That probably sounds like a stupid question but I'm just not sure what we actually need to know because it only says we have to 'describe condensation polymerisation to form' and then lists them so it's pretty vague

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Yes, any named polyester or amides will have the structure given in the exam, you don't to remember any specific examples, just the general formula.

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