If i take a crude nmr of my reaction mixture containing one reactant and product without adding any internal standard , is it possible to calculate yield of product integrating distinguish peaks of reactant and product?
It should be possible to use quantitative NMR techniques to estimate the yield.
The estimate error and uncertainty depends on:
- the signal-to-noise ratio for the resonances of interest
- the degree of baseline distortion (deviation from a perfectly flat baseline)
- well-separated resonances of interest such that overlap with nearby peaks is avoided
- an acquisition delay that is at least three times longer than T1 for the resonances of interest.
It would be best if you used an internal standard. If you don't want to add it when you are preparing the NMR tube, make sure it won't mess with your reaction and add it among the other starting materials.
Can you elaborate your answer in accordance to my question and yes precisely please.
It depends what level of accuracy you require. In simple terms, identify a signal from your product and one from your reactant, integrate and normalise these for the number of protons that they represent and these numbers will give you the molar ratios of the product and reactant. There is no need for an internal standard in this case.
There are caveats. This method assumes that your reactant only produces product and that there are no by-products. If there are by products then you could also integrate signals from these. Alternatively, use a reference signal such as ERETIC2 or QUANTAS and this will allow you to quantify independently.
If you require accurate results, then you need to follow William C Hutton's comments about signal-to-noise, etc. - particularly relaxation delays!
- Badges
- Science topic
- Similar topics
- Analytical Chemistry
- Column