OCR A Chemistry F324 Rings, Polymers and Analysis Thu 26 Jan 2012

How did you get those answers??

well it's just a case of looking at the stuctures and identifying the hydrogens which are in unique environments.

Once you've done that you see how many are in each environment and this is the relative peak areas.

The splitting is using the N+1 rule where n is the number of hydrogens bonded to adjacent carbon atoms.

Then you get the location on an nmr from the information sheet which gives the range of where certain environments will appear.

(edited 12 years ago)

Reply 581

Legendrew

Original post by arvin_infinity

So its quartet..quintet ..hextet..heptet..then wat ?! octet ...

yep then nonet and decet then it gets a bit complicated... lol

Reply 582

jmillslittle

When spin spin coupling gives you information about the number of protons on the adjacent carbon - how do we know which carbon is adjacent if there is more than one with protons? :s-smilie:

Reply 583

Stevo F

18

Original post by jmillslittle

When spin spin coupling gives you information about the number of protons on the adjacent carbon - how do we know which carbon is adjacent if there is more than one with protons? :s-smilie:

you count EVERY adjecent carbon which has hydrogens attached to it :smile:

Reply 584

jmillslittle

Original post by Stevo F

you count EVERY adjecent carbon which has hydrogens attached to it :smile:

then what chemical shift would we use- how do we chose between the two etc?

Reply 585

Stevo F

18

Original post by jmillslittle

then what chemical shift would we use- how do we chose between the two etc?

dont entirely know what you're talking about here... I'm guessing you mean which Hydrogen does the shift refer to? in which case on the data sheet its put the hydrogen in question in bold :smile:

Reply 586

jmillslittle

Original post by Stevo F

dont entirely know what you're talking about here... I'm guessing you mean which Hydrogen does the shift refer to? in which case on the data sheet its put the hydrogen in question in bold :smile:

k caught on. Im not trolling, just very tired :tongue:

Reply 587

PeterStoba

I sort of get what he means!

Say for example you had CH3 -- CH2 -- C6H5

We are looking at the NMR for the middle Carbon, with two Hs on. The adjacent carbon to the left would have a different chemical shift value as it's aromatic and not a methyl?

Reply 588

Stevo F

18

Original post by jmillslittle

k caught on. Im not trolling, just very tired :tongue:

I believe you :wink:

I didnt get ANY of organic chemistry while it was being taught, fortunately it's all "clicked" within the last couple of weeks which is lucky really, considering the exam's tomorrow :biggrin:

Reply 589

arvin_infinity

3

Wat would you guys say if Q come up asking how NMR works !

Reply 590

Oromis263

2

Original post by Stevo F

I believe you :wink:

I didnt get ANY of organic chemistry while it was being taught, fortunately it's all "clicked" within the last couple of weeks which is lucky really, considering the exam's tomorrow :biggrin:

Organic Chemistry > Inorganic Chemistry.

However, Physics > Further Maths > Maths > Chemistry, so it looks like inorganic chemistry is the worst! For me at least :wink:

Anyone else write little stories about angry customers when asked about chiral compounds? God damn litigation.

Also, how would you identify an unknown carbonyl compound! Show all varieties (60 marks)

^^^^ again, another way I'd like the paper to go.

Reply 591

Legendrew

Original post by arvin_infinity

Wat would you guys say if Q come up asking how NMR works !

I'd complain since it isn't on the spec to know how it works :rolleyes:

Reply 592

PeterStoba

Original post by arvin_infinity

Wat would you guys say if Q come up asking how NMR works !

Spec says;

Background theory will not be tested on
examination papers: the emphasis is on
the interpretation of spectra. Thus,
candidates will not be tested on why
nuclear magnetic resonance takes place,
the reasons for different chemical shift
values, why spin–spin splitting occurs or
why 13C NMR requires proton decoupling.

The most detail we need is;

state that NMR spectroscopy involves interaction
of materials with the low-energy radiowave
region of the electromagnetic spectrum;

Reply 593

Stevo F

18

Original post by arvin_infinity

Wat would you guys say if Q come up asking how NMR works !

Shifts only appear where the nucleon number is odd, in this case atoms have spin and when a large electric field is supplied around the atoms, they oscillate back and forth. The voltage can then be measured which gives us a shift pattern we can use to identify compounds.

Or something like that ^^^ :P

Reply 594

Stevo F

18

Original post by Oromis263

Organic Chemistry > Inorganic Chemistry.

However, Physics > Further Maths > Maths > Chemistry, so it looks like inorganic chemistry is the worst! For me at least :wink:

Anyone else write little stories about angry customers when asked about chiral compounds? God damn litigation.

Also, how would you identify an unknown carbonyl compound! Show all varieties (60 marks)

^^^^ again, another way I'd like the paper to go.

how can you think that when you do further maths? Inorganic chemistry is mostly just maths :P

Reply 595

Oromis263

2

Original post by arvin_infinity

Wat would you guys say if Q come up asking how NMR works !

I would be OVER THE MOON. I managed to luckily do some work experience at the Institute of Neurology at UCL and I worked with the NMR machine there.

Also, protip, don't forget the effects of D20 in NMR! And use CDCl3 as the solvent etc.Oh, and TMS (tetramethyl silane) is the reference point!

Reply 596

arvin_infinity

3

Original post by Stevo F

Shifts only appear where the nucleon number is odd, in this case atoms have spin and when a large electric field is supplied around the atoms, they oscillate back and forth. The voltage can then be measured which gives us a shift pattern we can use to identify compounds.

Or something like that ^^^ :P

+repped
yh sounds right to me ..they wouldnt ask more than that !

(edited 12 years ago)

Reply 597

Oromis263

2

Original post by Stevo F

how can you think that when you do further maths? Inorganic chemistry is mostly just maths :P

It bores me.

Reply 598

arvin_infinity

3

Original post by Oromis263

I would be OVER THE MOON. I managed to luckily do some work experience at the Institute of Neurology at UCL and I worked with the NMR machine there.

Also, protip, don't forget the effects of D20 in NMR! And use CDCl3 as the solvent etc.Oh, and TMS (tetramethyl silane) is the reference point!