The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Aqa chem 4/ chem 5 june 2016 thread

Scroll to see replies

Anyone know what the catalyst is for alkene to polyalkene?
Original post by Super199


You just have to use the information you gathered before to piece everything together. You can tell by Spectrum 1 which doesnt have an m/z peak at 133 and 105 that it cant be 'B,C, or D' because if the 'CH3CH2' on the 'CO' in B were to be fragmented off, the m/z peak would be 105. and If you look at C and D, if the 'H' on the 'CO' group were to be fragmented off, it would give an m/z peak of 133. And it says for spectrum one that it doesnt have these ones, and by process of elimination... it has to be A
Original post by JammyW15
You just have to use the information you gathered before to piece everything together. You can tell by Spectrum 1 which doesnt have an m/z peak at 133 and 105 that it cant be 'B,C, or D' because if the 'CH3CH2' on the 'CO' in B were to be fragmented off, the m/z peak would be 105. and If you look at C and D, if the 'H' on the 'CO' group were to be fragmented off, it would give an m/z peak of 133. And it says for spectrum one that it doesnt have these ones, and by process of elimination... it has to be A


Why can't spectrum 2 be C?
Original post by Manexopi
I'm preparing myself for a chromatography question. Last years paper was so nice but they literally asked all the questions I wanted so doubt we'll see them. I hope they leave out the nmr spectra questions and just make us draw the compounds from the formula and little facts they give.


I know! I was so happy with last years paper, the questions were actually perfect....Im starting to worry now because I feel like it will be completely different :afraid:
Original post by Super199
Why can't spectrum 2 be C?


Spectrum 2 Is C :smile:
Reply 385
Avatar for 12284
12284
8
Original post by JammyW15
Spectrum 2 Is C :smile:


How can you tell whether molecule D is spectrum III or IV? Because both spectrums have no peak at 119?
Original post by Splashoid
The rate determining step will always have the compounds in the rate equation (or compounds derived from it).
If that doesn't make any sense, could you give an example of a question? I could try to work through it.


But sometimes both species are present in two different reactions , so how would I know?


Posted from TSR Mobile
In Nucleophilic Addition reactions, I have in my notes that to generate a hydroxy-nitrile from an aldehyde or ketone, you can use either KCN or HCN, is this right?

Surely if you used KCN then the second part of the mechanism, where the negatively charged oxygen donates its electrons to the H+, wouldn't occur? Or would the H+ still be generated from the dilute acid catalyst?

Thanks in advance!
Original post by cutelady
But sometimes both species are present in two different reactions , so how would I know?


Posted from TSR Mobile


You take the slowest step
Original post by Coolworm
In Nucleophilic Addition reactions, I have in my notes that to generate a hydroxy-nitrile from an aldehyde or ketone, you can use either KCN or HCN, is this right?

Surely if you used KCN then the second part of the mechanism, where the negatively charged oxygen donates its electrons to the H+, wouldn't occur? Or would the H+ still be generated from the dilute acid catalyst?

Thanks in advance!


You can do it with KCN, the H+ will come from the solvent.
Original post by Parallex
You can do it with KCN, the H+ will come from the solvent.


Okay thank you, the solvent being H2SO4?
Original post by Coolworm
In Nucleophilic Addition reactions, I have in my notes that to generate a hydroxy-nitrile from an aldehyde or ketone, you can use either KCN or HCN, is this right?

Surely if you used KCN then the second part of the mechanism, where the negatively charged oxygen donates its electrons to the H+, wouldn't occur? Or would the H+ still be generated from the dilute acid catalyst?

Thanks in advance!


KCN is in ethanol - so the H+ could come from the solvent or the catalyst :biggrin:!
Original post by Coolworm
Okay thank you, the solvent being H2SO4?


Yeah that's what I've got in my notes - dilute H2SO4!
Original post by 12284
How can you tell whether molecule D is spectrum III or IV? Because both spectrums have no peak at 119?


Its gonna have to be III because it can have a peak at 133 if it loses the 'H' attached to the 'CO' Group. Spectrum IV says the molecule can't have that
Does anyone know why vdw forces act between terylene molecules instead of hydrogen bonding?

Posted from TSR Mobile
Original post by SubwayLover1
KCN is in ethanol - so the H+ could come from the solvent or the catalyst :biggrin:!


Original post by Parallex
Yeah that's what I've got in my notes - dilute H2SO4!


Ok, thank you both! :biggrin:
Reply 396
Avatar for 12284
12284
8
Original post by JammyW15
Its gonna have to be III because it can have a peak at 133 if it loses the 'H' attached to the 'CO' Group. Spectrum IV says the molecule can't have that


How can any of the molecules be spectrum IV then because can't they all lose 1 hydrogen? The answer is meant to be molecule B for spectrum IV but can't it lose a hydrogen from "CH3"?
Reply 397
Avatar for dnan
dnan
2
Why does water only very slightly dissociate?
Original post by Azzer11
Does anyone know why vdw forces act between terylene molecules instead of hydrogen bonding?

Posted from TSR Mobile


Would never be hydrogen bonding because it's just benzene, C=O, C-O and C-H so I think it'd be dipole-dipole forces and van der Waal's. Hydrogen bonding is only between hydrogen and N, O and F.

Kevlar on the other hand would have hydrogen bonding
Original post by Azzer11
Does anyone know why vdw forces act between terylene molecules instead of hydrogen bonding?

Posted from TSR Mobile


No X-H bonds which have a great enough electronegave difference for there to be any sort of hydrogen bonding.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you