Dear Michele Larocca, Thank you for your reply. I read some where that internal standard can be use to calculate %yield of product.  

Even in the good old days you could integrate peaks. Thus, forget about measuring peak heights with a ruler!!!. Peak shapes (heights, line-broadening etc.) vary among others with the relaxation time, homogeneity etc.. Internal standard is a known amount of a compound of your choice, which dissolves in your solution and does not react (inert) with any of your other component or with your NMR solvent. Preferably, you chose an internal standard whose signals (chemical shifts) will not overlap with any of your component. As implied above, you need to weigh in the internal standard, so you can calculate its molarity. Then after taking the spectrum you need to carefully integrate your peaks. If you have broader peaks or just for higher accuracy it is advisable to increase T1 up to 10 sec (or more) and/or record spectra at different T1-s and compare. One proton of your internal standard corresponds to that molarity. If the chosen signal(s) of the internal standard consist(s) of more protons (2 or 3) you need to divide it(them) accordingly(by 2 or 3, respectively). The same goes (division in case of multiple protons in a pattern) for the signals of you product or starting material. In this way by calculating the molar ratio from the integral ratio of your product or starting material as compared to the internal standard you can have the molarity of any known or identified compound (which resolves well) in your spectrum. Note, that this way you can calculate conversion and yield only to known and detected (or detectable) components. Unknown products needs to be identified first. When you have undetected products your conversion will be higher than the detected total yield of products.

% yield could be a question of how much product vs how much starting material is remaining, then yes, the ratio of known integrals from product and from starting material will indicate %yield, and is quick and rough, provided you have access to the electronic data or a spectrometer. If not, a ruler is a last but workable resort! % Purity is more involved, but along similar lines. In both cases, IT above has presented an excellent summary of how to proceed. Note that it is possible to use the residual solvent peak as an internal standard without adding another standard. see Pierens, J. Nat. Prod.2008 ,71, 810–813. For general review see Trends in Analytical Chemistry, 2012, 35,5, for methods, developments and applications.

Sounds like you would want to do a bit of qNMR.  See J. Nat. Prod. 2005, 68, 133-149 for a nice introduction.  Table 1 has a 'cookbook' approach you can use.  An easy thing to do, to get decent numbers, is to set your relaxation delay to 5 times the longest T1 in your sample (so you will need to measure that) to allow enough time for full relaxation.  There are a number of other things to take into consideration (like integrating the 13C satellites or decoupling them) that are detailed in that paper and others. 

Perhaps we were talking about two different things. An NMR reference is a compound with a known chemical shift to adjust the scale properly. Beside the frequently used TMS, this can also be CHCl3 in your CDCl3 in 1H NMR for this purpose. An internal (or external) standard is used for quantification as described above. You can also use your NMR reference for quantification as far as you know its concentration (wt%) in your solvent and you weigh in your solvent and reactants. By the way, I remember the good old days in GC, when we did not have integrators. At that time we used the peak height multiplied by the half-width (peak width at half height). Please don't use peak heights for calculating component ratios because the relaxation time (peak shape and broadening) can be very different for different compounds in NMR. Not to mention other effects such as a quadrupole atom in the neighbourhoud, an exchange process etc.

So suppose I am using internal standard (2 mg) consists of 1 proton. Reaction mixture (5 mg) is showing integral of product proton is 0.73 and starting material is 0.25 in NMR spectrum. Does it indicates molarity directly? what to do after getting this integrals? It would be your great help. 

So, if the integrals represent one H each, then it sounds like you have a ~3:1 molar ratio  of product to starting material. In order to calculate the amounts by mass, then you need to include the molecular weights of the product, the starting material and the standard in your calculations, as well as the standard.

Dear Krupal,

For your specific case: 1. Calculate the molar amount of your internal standard by dividing 2 mg with the MW of your internal standard. You have probably weighed in the starting material, so you can calculate its molar amount too. After the reaction, look for patterns of your starting material, which is(are) well-separated from the rest of the spectrum. (You can but you don,t need to integrate all the peaks). Integrate the signal of your internal standard and your selected starting material signal(pattern). If the latter corresponds to 2 or 3 protons you need to divide the integral value by 2 or 3 respectively, to get the 1-H equivalent. Then the integral ratio of your 1-H starting material and the 1H equivalent of your internal standard will give you the molar ratio of your residual starting material to the internal standard. Multiplying this with the mols of the internal standard will give you the molar amount of your residual starting material.(Conversion=100- (mol residual starting material/mol starting material) x 100). You can then apply the similar procedure for your product(s). The integral ratio of your 1-H product(s) equivalent and the 1H equivalent of internal standard will give you the molar ratio of your product(s) to the internal standard. The(ir) molar amount(s) can be obtained similarly as described above. (Yield= mol product/mol starting material x 100; Selectivity= mol product/ (mol starting material - mol residual starting material) x 100, These can also be calculated on the appropriate 1H equivalents). In other words for your question, NMR integrals are directly related to molarity, only you need to take care that integral ratios are always calculated for the same amount of protons in your internal standard and sample. If you want more accurate analysis, what above is written (relaxation time, undetectable or overlapping peaks, etc.) are also important. Hopefully, this helps you calculating your data.

Regards,

 Dear Krupal, 

Follow Professor Tóth's excellent instructions above. And, as he already pointed out, please do not use rulers, peak heights, but integrals if you want to get correct results. NMR is a great tool for quantitative analysis if it is done properly, with care. 

Good luck.

While I just glanced at the many responses, nowhere did I see mention that the spectra from which you wish to extract the information you are after must be acquired under fully relaxed conditions.

Ian is correct. But I believe that this is already pretty much covered in Prof. Tóth's excellent instructions.  Adequate delay between pulses is a requirement for quantitative analysis.

Yeah, The information provided by Prof. Tóth is very helpful. Thank you Anthony Foris and Prof. Ian M Armitage too. There are so many publication in organic chemistry published in which they mentioned yield from proton NMR but I think more practical and step by step information might get from personal experience.

Hi,

I have a doubt while calculating the % conversion of starting material. How to give the internal standard integration in case of mesitylene ?. I'm doing time vs conversion, but I'm not getting same integration value for the Internal standard (IS) in all cases, even though I'm adding the same amount of IS. 

Hi Pcrao varikuti,

As reaction time increases, you will get more product and accordingly more concentration of product and less concentration of starting material., so obviously with respect to product proton you will get less integration value for internal standard. I hope this will clear your doubt. 

Hi Krupal,

Thank you very much. I have one more doubt, How to calculate the % yield from the NMR data? I'm getting integration for IS is 9.00, when I'm keeping 1.00 for product proton (every time IS is 10 uL).  In the above one professor explained the calculation, but in that IS moles is not included, I think so. Please explain me briefly.

Thanks in advance.

Can you drop a massage with your email ID. I will send you a article from which you will get clear idea. 

Hi,

My email.ID [email protected]  please send the article. 

Thanks in advance.

Hi Krupal Jethava,

I did not get the article.Please send it.

Thanking you.

I agree with Prof Toth's nice explanation. I want to add some more things to make it more simpler. 

1. Identify characteristic peak of your product and chose suitable internal standard, I.S. (mesitylene, DMF) based on lowest no. of peaks. The peak(s) of  SI  should not merge or come in the range of starting material and product.

1. Take known wt. (not volume) of internal standard and commercially pure product in NMR tube and analyze to correlate the percentage of actual and calculated amount of product based on Troth's method.

2. After establishing a good correction, the product samples can be run as in 2 to calculate product's yield.

Dear all,

I just a little bit confused about the internal standard? 

In NMR case, Dose the deuterated solvent itself serves as the internal standard?

Thanks 

Hi Krupal,

You kindly attached the article that you sent to Pcrao in this conversation so all followers will get benefits from it.

Best regards

http://onlinelibrary.wiley.com/doi/10.1002/mrc.3906/abstract

@Madayan Yaseen- If your question is just to quantify your product with IS, I will simply say no. The concentration of IS which is present in the NMR solvent is difficult to quantify/measure in the volume used in NMR tube during the analysis. The exact concentration of reactant and the product available in the NMR tube during the analysis is necessary for the quantitative analysis of the product(s).

Hope I have answered your question

@Madayan Yaseen The peaks observed for deuterated solvent in 1H NMR is correspond to the residual protons present. So it is not quantitative, hence cant be used.

I am also want to know the details what about said Basant Mohamed

Regards

Mahmud

Manikandan Selvaraju: the residual 1H solvent peak in the deuterated solvent has actually been used as an internal quantitative standard for NMR, provided that it is first calibrated (for details see):

"Determination of Analyte Concentration Using the Residual Solvent Resonance in 1H NMR Spectroscopy" Gregory K. Pierens, et al., J. Nat. Prod., 2008, 71, pp 810–813; DOI: 10.1021/np8000046

I attached the procedure about how to calculate NMR yield. you can follow the steps

please find the attached link to calculate NMR yield. But i always prefer isolated yield.

http://www.organ.su.se/bo/Gruppfiler/NMR%20yield%20calculation.pdf

when our product decompose on silica gel column, or significant lose during extraction, we often help from quantitative NMR to show the actual yield before purification. i hope the following document will help to calculate NMR yield.

Sorry, but the assumption that proton-NMR's integrals ratio of two different compounds (Analyte & Standard) is related to the molar amounts is absolutely not right for a standard NMR Experiment!

Compounds (their protons) have different relaxation times... after the puls delay, one compound might "have relaxed more" than the other when the FID is "cutted". You will loose more information from one compound than for the other. This oftenresults in non-molar ratios of the integrals! Only when the relaxation times of both compounds (longest T1 of their protons) is equal, the quantification will be correct.

For qNMR experiments, you need to determine the longest T1 values from both compounds (inversion recovery experiment) and set the puls delay pd = 7x T1.

also 2-3x T1 would be enough for rough quantification