Post by: Jazz_Blue on May 30, 2012, 01:35:35 am
2) In high resolution proton NMR, how many splitting are there for propanol? how many will CH2 split? ( since there is a CH3 and also CH2 and OH next to it)
Post by: pi on May 30, 2012, 01:56:56 am
1) 4 environments, basically, the each H attached to a different carbon is in it's own environment (so that's 3 environments) and then the H in the -OH is in it's own environment too, so 4 in total
2) There will be four environments: 3 peaks (-CH3), 6 peaks (the CH2 in the middle), 3 peaks (the CH2 connected with the OH) and 1 peak (the H from the OH)
I think that's right :S (my chem is very very rusty)
Post by: thushan on May 30, 2012, 12:22:49 pm
Propan-1-ol: 4 proton environments, a singlet (OH), a triplet (carbon-1), a triplet of a quartet (a 12-et) (carbon-2) [multiplicity rule, not sure whether you have to know it], and a triplet (carbon-3)
Propan-2-ol: 3 Proton environments, a singlet (OH), a doublet (carbons 1 and 3), and a septet (carbon 2).
Post by: pi on May 30, 2012, 01:39:33 pm
Post by: Ravit on May 30, 2012, 02:03:27 pm
Post by: pi on May 30, 2012, 02:08:55 pm
Post by: thushan on May 30, 2012, 02:18:56 pm
I gave the VCE response not taking into account multiplicity btw :(
Not sure what the VCE response is actually...because some schools actually do teach the multiplicity rule, my school and Pascoe Vale Girls' College (where I gave a talk last week).
Post by: pi on May 30, 2012, 02:23:07 pm
I gave the VCE response not taking into account multiplicity btw :(
Not sure what the VCE response is actually...because some schools actually do teach the multiplicity rule, my school and Pascoe Vale Girls' College (where I gave a talk last week).
I just assumed as MHS didn't teach it and Heinemann didn't mention it at all (and neither did A+ study notes or TSFX notes) that it wasn't on the course :P
As said before, I doubt VCAA would give an example like that to draw.
Post by: thushan on May 30, 2012, 03:37:58 pm
I gave the VCE response not taking into account multiplicity btw :(
Not sure what the VCE response is actually...because some schools actually do teach the multiplicity rule, my school and Pascoe Vale Girls' College (where I gave a talk last week).
I just assumed as MHS didn't teach it and Heinemann didn't mention it at all (and neither did A+ study notes or TSFX notes) that it wasn't on the course :P
As said before, I doubt VCAA would give an example like that to draw.
Yeah I doubt that too.
Post by: Ravit on May 30, 2012, 03:47:13 pm
Post by: charmanderp on May 30, 2012, 07:10:21 pm
Post by: Teen on May 30, 2012, 07:21:53 pm
Post by: thushan on May 30, 2012, 07:26:26 pm
According to the Access lecture, which was conducted by the chief examiner, you need to account for multiplets. It was about the only useful piece of information I gleaned that entire night.
Chris Dwyer mentioned that multiplicity rule is needed? FUQ. I stand corrected.
Are you sure? This is important because I made sure all my NMR qns in my book had no multiplicity issues.
Post by: thushan on May 30, 2012, 07:27:30 pm
Guys . It might sound stupid.seriously wat is multiples. Is it when u have a complex splitting .
yup! its when you have two neighbouring carbons that are in different environments.
Post by: Teen on May 30, 2012, 07:28:45 pm
Post by: thushan on May 30, 2012, 07:45:31 pm
Post by: charmanderp on May 30, 2012, 08:37:25 pm
According to the Access lecture, which was conducted by the chief examiner, you need to account for multiplets. It was about the only useful piece of information I gleaned that entire night.
Chris Dwyer mentioned that multiplicity rule is needed? FUQ. I stand corrected.
Are you sure? This is important because I made sure all my NMR qns in my book had no multiplicity issues.
Can't remember for certain if he said it was needed but we did about two questions involving the multiplicity rule.
Post by: pi on May 30, 2012, 09:26:09 pm
According to the Access lecture, which was conducted by the chief examiner, you need to account for multiplets. It was about the only useful piece of information I gleaned that entire night.
Multiplets or multiplicity? Multiplets are just any peaks that aren't singlets afaik...
He gave us (MHS and Mac.Rob) a lecture last year for Unit 3, and I'm pretty sure he said it wasn't on the course...
Either way, just like "cracking", learn it anyway if you have the time :)
Post by: rebeckab on May 30, 2012, 10:26:58 pm
Post by: Mao on May 31, 2012, 12:49:44 am
According to the Access lecture, which was conducted by the chief examiner, you need to account for multiplets. It was about the only useful piece of information I gleaned that entire night.
Multiplets or multiplicity? Multiplets are just any peaks that aren't singlets afaik...
Multiplets are peaks that cannot be distinguished as a simple n-tet or (tet)2, and so forth.
The
Also, if the difference is significant enough, and you have for example (1+1)*(2+1)=6 peaks, that is NOT a sextet. That is a doublet of triplets or triplet of doublets, depending on the strength of J-coupling. To name something n-tet, it must have the correct binomial height distribution (i.e. Pascal's triangle).
(http://upload.wikimedia.org/wikipedia/commons/e/e2/J-Coupling-complex-multiplets.gif)
Anyways, the point is you only need (n+1) splitting. A case can always be made that
Post by: charmanderp on May 31, 2012, 09:22:52 pm
I went to a lecture with Chris Dwyer a few weekends ago, and I am almost 100% sure he did not mention multiplicity, and it's not mentioned in his slideshow at all..
Fair enough, maybe I fostered it within my imagination due to how bored I was.