29 PROTON NMR Flashcards
In proton NMR, what about the relative peak area, what does it tell you
The ratio of the area simplifies to give the ratio of hydrogen atoms in the PROTOM ENVIRONMENT IN TOTAL
This could mean spread across different atoms but in same environment
What is spin spin coupling
How many peaks will be produced (rule)
What about the relative peak area heights , how are they shown?
Under higher resolution, the peaks of the proton split into different number of peaks based on the number of hydrogens on ADJACENT CARBONS
This will produce n+1 peaks in a binomial coefficients peak height
FOR SPIN SLIN COUPLING, WHAT IS THE RULE FOR WHAT CARBONS YIU ACC SEE
Super important
THEY MUST BE OF DIFFERENT PROTON ENVIRONEMNT, IF SAME, IT WONT SPLIT!!:
What happens with OH and NH protons?
They produce a BROAD PEAK and can’t form any spin spin coupling
How are Oh and NH protons identified, what’s the tehnciaue
(D2O?)
First run the spectrum, if you see a broad peak be wary as this means there COULD be an OH
Then add D2O in the mix , and this will replace with the OH
Now run a spec and the broad peak should dissoear as detutueated compounds never produce a peak
This way you know the broad peak was actually from OH or NH
Remember if they ask to draw Porto on spec, remember not to forget thr OH
just draw it random in thr spec, as long as it’s there great
Also remember some groups can be more chemical shifted due to more electronegative atoms
IMPORTANT
The Hc c=O group on the 2- 3 peak, can this be a carboxylic acid or DEFINITLY KETONE
be careful
If the thing is done with D2O, then it CAN STILL BE A CARBOXCYLIC ACID
If it’s fine without D2O, it must be a ketone
This should be confirmed by the IR spec
Also if there is D2O peak at 11, what does this mean
Not only is the OH appear, but it can be a WHOLE cabroylic acid too
DINT NEED one beforen
Conclusion about D2O peaks
Peak at 11 can disappear due to D2O, and that means it’s carbox
However if it is carbox and peak dissepars , there still could be a peak at 2-3, which means it’s cabrixykic , doesn’t have ti be both
Asymmetric CARBIN means?
Chiral centre
If it’s asymmetric it will have a chiral CARBIN
