How to read integration values (1 Viewer)

[rickypontingdagoat]

my teacher recommended this university book to try practice mod 8 Proton NMR questions and trying to identify compounds based on spectra given, and it seems to be a good resource, however I am wondering if there is a way to know what the integration values are on the H NMR graph or if in uni ur expected to calculate it or smth

 

[wizzkids]

The integrated peak heights are used to determine the number of protons in closely similar chemical environments.
Look at those stair-step graphs. The height of the step is the integrated value. The peaks at -1.3 and -2.0 have the same step height so they represent the same number of protons, and the step height at -4.2 represents only 3/4 the number of protons as the other two chemical environments. The peak at -2.0 is a singlet so that means these protons have no nearest neighbouring protons on the adjacent carbon atoms. The peak at -1.3 looks like a triplet and the peak at -4.2 looks like a quartet. In HSC Chemistry you should be able to interpret what doublets, triplets and quartets are caused by.

There are two types of instruments in labs for doing Proton NMR. The high-B field instruments can split the peaks and reveal additional structural information, and the low B-field instruments (i.e. the cheaper ones) can only generate a broad "integrated" peak. They can't separate the doublets/triplets etc. You can tell from the Larmor frequency whether a high-field or a low-field instrument was used. The precession frequency for protons is given by this relation, ω=42.58 x B so that 200 MHz scan was done with a B-field of about 4.5 Tesla which is pretty high.
You can also re-process a high-resolution scan so that it just gives an integrated peak for the doublets/triplets etc.
I hope this is not too confusing.

 

[rickypontingdagoat]

The integrated peak heights are used to determine the number of protons in closely similar chemical environments.
Look at those stair-step graphs. The height of the step is the integrated value. The peaks at -1.3 and -2.0 have the same step height so they represent the same number of protons, and the step height at -4.2 represents only 3/4 the number of protons as the other two chemical environments. The peak at -2.0 is a singlet so that means these protons have no nearest neighbouring protons on the adjacent carbon atoms. The peak at -1.3 looks like a triplet and the peak at -4.2 looks like a quartet. In HSC Chemistry you should be able to interpret what doublets, triplets and quartets are caused by.

There are two types of instruments in labs for doing Proton NMR. The high-B field instruments can split the peaks and reveal additional structural information, and the low B-field instruments (i.e. the cheaper ones) can only generate a broad "integrated" peak. They can't separate the doublets/triplets etc. You can tell from the Larmor frequency whether a high-field or a low-field instrument was used. The precession frequency for protons is given by this relation, ω=42.58/B so that 200 MHz scan was done with a B-field of about 4.5 Tesla which is pretty high.
You can also re-process a high-resolution scan so that it just gives an integrated peak for the doublets/triplets etc.
I hope this is not too confusing.

Thanks, that helps a lot.