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Chemistry unit 6 June 2016

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Original post by TheMadHatteress
Morle ekshathe morbo shobai :3


TRUE
Original post by xbuttermelon
Nooo I didn't forget about the OH in carboxylic part...lemme show you what I mean and correct me if I'm wrong please.
image.jpg


Um, it is incorrect, all hydrogen environments are different, so 5 peaks present
Original post by 12103763d
Um, it is incorrect, all hydrogen environments are different, so 5 peaks present


I see. Thanks
Original post by 12103763d
Um, it is incorrect, all hydrogen environments are different, so 5 peaks present


umm no they aren't
Original post by anonymousawesome
umm no they aren't


Original post by 12103763d
Um, it is incorrect, all hydrogen environments are different, so 5 peaks present


I don't really understand why they are 5, but just asked my chem teacher & said that there are 5 different environments, so the other people must be correct...more like, the answer I crossed out was correct *sob*
What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization
Original post by Quirky01
What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization


I wrote it was the 3 something isomer?
Reply 287
Avatar for RizK
RizK
20
Original post by xbuttermelon
Nooo I didn't forget about the OH in carboxylic part...lemme show you what I mean and correct me if I'm wrong please.
image.jpg


no it is not one hydrogen environment, they are different distances away from the oxygens
Original post by xbuttermelon
I don't really understand why they are 5, but just asked my chem teacher & said that there are 5 different environments, so the other people must be correct...more like, the answer I crossed out was correct *sob*

U need to extend along the chain until the end to derive whether it has same proton environment, which means u should not just see the adjacent carbons attaching same number of hydrogens then derive they have same proton environment
Reply 289
Avatar for RizK
RizK
20
Original post by Quirky01
What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization


I wrote it should be the 148 degrees one because impurities can only cause the melt. temp to be lower - so it cant be 142 (range is 144-146) Therefore if recrystallization is carried out again and the sample is furhter purified the mlting temperature would increase and go closer to 148.

I was honestly clueless whether recrystallisation is done twice though. xD
Original post by 12103763d
U need to extend along the chain until the end to derive whether it has same proton environment, which means u should not just see the adjacent carbons attaching same number of hydrogens then derive they have same proton environment


Ohh! Thank you! Now I understand....need to go over this topic just incase they bring this nmr stuff in unit 5 :frown:
Original post by RizK
I wrote it should be the 148 degrees one because impurities can only cause the melt. temp to be lower - so it cant be 142 (range is 144-146) Therefore if recrystallization is carried out again and the sample is furhter purified the mlting temperature would increase and go closer to 148.

I was honestly clueless whether recrystallisation is done twice though. xD



I thought that the temperature range after recrystallization was 144-146.
So I wrote that it should be the 3 something isomer since it is within that range of temperatures :O
Reply 292
Avatar for tgygt
tgygt
2
Original post by anonymousawesome
What did you guys write for the ammonium disulphate question?


What is this question?
Reply 293
Avatar for Aimen.
Aimen.
OP
7
Original post by Quirky01
Could no. Of paeks in low res nmr be used todistinguish P, Q and R? What are your answers guys?


I wrote P and Q couldn't be distinguished bcz both have 4 proton environments but R could be as it had 2!
Reply 294
Avatar for RizK
RizK
20
Original post by notsoclueless
I thought that the temperature range after recrystallization was 144-146.
So I wrote that it should be the 3 something isomer since it is within that range of temperatures :O


There was none in the range.. temperatures were
138, 142, 148
range falls between the second and third
equally
I was talking about a second recrystallization i e further purification
Reply 295
Avatar for Aimen.
Aimen.
OP
7
Original post by Quirky01
What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization


It was P with 148c
Reply 296
Avatar for Begad
Begad
In January 16, the A* was 31/50 and full marks were 34/50 so there still hope!! This is the hardest paper I've ever solved and studying past papers didn't even prepare you for the exam. I literally wanted to cry after it😭😭😭😭
Original post by Aimen.
It was P with 148c


But why? After recrystallisation range was 144-146
I wrote that it would contain p and q in sample B cos avg of their melting temp gave 145 degrees which is in the middle of the range after recrystallisation..
I might be wrong..very unsure..
Original post by AvWOW
haha yeah ooops I meant that.
Oh and with excess ammonia it was Zn(NH3)4 ^2- or Zn(NH3)6^2- ???


It's Zn(Nh3)4^2-
Original post by Sandy_Vega30
It's Zn(Nh3)4^2-

The charge should be 2+
And I think it does not matter whether it's 4 or 6

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