With increasing concentration of the same compound will proton integral differ?
I am using the software "Mestrenova" to plot my nmr data. Doing multiple integral for certain peaks gives me values in the range of 1-5. However when I change the parameter to "derivative" in multiple integral option I am getting values in the range of 1000. What does this mean?
Will I be able to quantify my compound only using proton integral?
Integrals reflect the relative number of protons in a specific moiety for a given compound. Usually we normalize the integrals with respect to one of the signals for which we are certain of the assignment and hence know the number of protons. Since increasing concentration doe not change the molecule itself, your integrals should not change.
I'm not sure about what problem you're having with mnova. But you should be able to quantify the protons in your system with just proton nmr. If you have quaternary carbons you'll need to run 13C nmr.
Hi Aarthy,
the integrals they describe in the text are the peak area which is given from the software. As Rudraksha already mentioned, not the integral values itself are important (depending on the concnetration), but the ratio to each other. The spectrum is "scaled" to one CH3 group, -CH=CH- group or anything you really know that this is the exact numbers of protons. The rest is just calculation - integration areas of other protons are divided by that number and you get "even" numbers such as 1, 2 or related. For example: In the text they take the -CH=CH- group as reference, the integral is ~ 500. The CH-group of the DHA acyl has integral of ~275, which is 0.5 of the -CH=CH-. Since for this group you know that this are two protons, you know that the signal at 1.9-2.2 is one proton. If they would have set the double concentration of that compounds, the integrals would be 1000 and 500 respectively, but still the ratio is 0.5, so 2 protons and 1 proton.
Also certain groups do have signals on certain ppm values, depending on the surrounding. Electron withdrawing groups such as OH or COOH are at high ppm values, CH3 and related at lower values. This will give a secont hint which signal is which.
Btw: I never saw publications where they give the integrals of the peaks, usually you just tell the ppm, if it is a singlet, doublet, multiplet etc... and the group. E.g. Like this: 1H NMR, (250.13 MHz, CDCl3): δ [ppm] = 7.34 (m, 15H, Ph), 6.43 (s, 1H, NH) and so on.
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