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Aqa chem 4/ chem 5 june 2016 thread

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For the lidocaine HCL question I said as a salt is was readily soluble, and the Lidocaine could be diluted if needs be.

Structure for last Question I got was CH3OCH2CH2C(CH3)2OH, just put what structures each chemical shift would be - wrote that it was a 1/2 alc and there was no CC double bonds present since that was all you could pull up from what they told you.
Original post by chloeabeki
I wrote my numerical answers on my formula sheet and took it out, these are what I got...
pH values of 2.08, 2.32 and 2.33
1.204 for the salt/acid ratio
0.33 mol and 4.16 mol
9.09x10^-3 for something (kc?)
9.402% hydrogen
112 for the molecular ion peak
K=3.12x10^-5


Completely agree.
Original post by cuppycake3
no one laugh but could it be

(ch3)3-c-o-ch2-ch2-o-h

i came up with that in two mins :frown:((((((((



Haha I got that too, but I couldn't get the structure so I was just like 'screw this' and drew some structure which looked alright to me....
Original post by haj101
Are you joking?😱


Only the last question was a discriminator.
Original post by Cadherin
That wasn't too bad, just a bit unlike past papers and I was REALLY pushed for time. I finished as she said 'pens down'.

Did anyone else get the rate expression as exactly the same in the question?

Also, what was the reason for lidocaine hydrochloride? I said to prevent the N acting as a base by protonating it and so reduces side effects. I spent about 5 minutes looking for a chiral carbon in that compound to talk about enantiomers, but I couldn't see one!


wasn't too bad? Are you sure about that?
Original post by Joxnna_
nitrogen atom b had more alkyl groups (inductve effect etc) but a had an N-H bond, making that part of the molecule more soluble therefore more likely to react... right?? urgh, worst paper ever


I put B because of the alkyls, occasionally the mark schemes allow either if they're more interested in your reasoning.
What were the reagents and conditions in the organic synthesis question?
Original post by Sani Ej
For the rate equation i put the same as the one they gave us i thought it had no effect :frown:


I agree. The only thing affecting Kc is temperature - thus rate will only depend on the differing ratio of propanone to protons.

Don't worry, others said they found it hard, I suspect 120 UMS will be no higher than 90.
For the lidocaine salt question I said it was a salt so it was a solid so it could be eaten instead of injected, don't even ask, I don't know wtf I was thinking, I just wrote anything I could think of, I actually find it quite hilarious how bad that exam went
What did people put for the mechanism on the second question??
Original post by jakeysimps11
Same mate, 99% sure its correct


I put that but its wrong, that gives you a tertiary alcohol and it doesn't form a green ppt
Original post by janvi24
I got the same


Yay! A mark! Now up to 4! :biggrin:
Original post by Cadherin
That wasn't too bad, just a bit unlike past papers and I was REALLY pushed for time. I finished as she said 'pens down'.

Did anyone else get the rate expression as exactly the same in the question?

Also, what was the reason for lidocaine hydrochloride? I said to prevent the N acting as a base by protonating it and so reduces side effects. I spent about 5 minutes looking for a chiral carbon in that compound to talk about enantiomers, but I couldn't see one!


I got the rate equation the same, but I guessed.

The reason for lidocaine hydrochloride (and I might be wrong) is the response the person below said minus the diluted bit.

Original post by RME11
For the lidocaine HCL question I said as a salt is was readily soluble, and the Lidocaine could be diluted if needs be.

Structure for last Question I got was CH3OCH2CH2C(CH3)2OH, just put what structures each chemical shift would be - wrote that it was a 1/2 alc and there was no CC double bonds present since that was all you could pull up from what they told you.


I said that it was a soluble ammonium salt that can be converted back into an amine by addition of NaOH
Original post by ethanstoddart
Thought I had it then turns out I made a tertiary alcohol :p:D


Thats what i did! Because my structure added up with the H n.m.r it was just a joke!
Original post by cuppycake3
no one laugh but could it be

(ch3)3-c-o-ch2-ch2-o-h

i came up with that in two mins :frown:((((((((


Very nearly it was ch3-o-ch2-ch2-c (ch3)2 (oh)
Original post by scienceman
What were the reagents and conditions in the organic synthesis question?


Step 3 was a substitution question to go from Br to a CN group. So I said KCN aqueous and alcohol.

The final step was reduction, so Hydrogen & Nickel Catalyst.
Original post by scienceman
What were the reagents and conditions in the organic synthesis question?


I think this is what I put:

KCN ethanolic aqueous solution

then

LiAlH4 ether
Original post by GabrielSmith1998
wasn't too bad? Are you sure about that?


I hope so :/

When I say 'wasn't too bad', I mean, compared to the potato in AQA physics last year, not too bad.
Original post by High Stakes
Only the last question was a discriminator.


Do you have nothing better to do?
Original post by scienceman
What were the reagents and conditions in the organic synthesis question?


ethanolic KCN and AlLiH4 in ether (or hydrogen with nickel catalyst)

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