Hello I am new here as I am have struggle with the following.
I did a nitration of phenole using potassiumnitrate and sulfuric acid.
The raw product was seperated via a column chromatography using 10:1 cyclohexane:ethylacetate to get the o-nitrophenole and later 5:1 to get the p-nitrophenole.
I did the chromatography (please see attached table for an overview of the first column I did; all TLC were run with 5:1 except Vial 1-14 there were run with 10:1) and got multiple fractions. As I did this procedure before I figured that the yellow kinda dirty product that came with the 10:1 should have been the o-nitrophenole and the orange product the p-nitrophenole. The solvent 10:1 was switched to 5:1 after vial 30.
Normally the column should go like o-nitrophenole (F3), then some chinone byproduct and the as the most polar product forming H-bondy with the silica the p-nitrophenole (F4), when using the 5:1.
But after taking melting points, NMR and MS the results are really confusing.
Fraction 3 the yellow solid was clearly p-nitrophenole and came with the 10:1 solvent. Fraction 4 an orange solid showed only slight peaks beside solvent and impurities in the nmr that indicate a mixture of everything. The MS showed nothing as the compound was able to ionize. Please not that vial 15-26 were leftover but i added vial 17-26 to fraction 3 and did a secound column to make the product more pure. All fractions of this secound column showed only one compound on the TLC (not to sure about that, only took a TLC of every 4 vial). The NMR attached of F3 that was done after the second column also seems to be not mixed with o-nitrophenole so I guess there was no o-nitrophenole in the secound column and therefore also not in vial 17-26.
My really important question now is what happend to the o-nitrophenole, as before the fraction with the p-nitrophenole (F3+Vial 17-26) I only got black tar and vials that are non active on the TLC.
I have used 5.06 g of potassiumnitrate in 10 ml of water, added 2.7 ml sulfuric acid at 15-20 °C and then added 2.36 g of phenole diluted with 0.25ml of water.
Water and Ethylacetat was added and the aquarious phase was extracted with ethylacetat. This was really messy as it was really hard to seperate the really dark layers of liquid.
I got 2.657 g of raw product and then proceeded with the column chromatography.
Every help or input is really appreciated as I missed the yield and purity for this experiement now for the second time. Now everything depends on a solid protocol to not redo the whole organic chemistry lab next summer for like 2.5 months...helps
The fraction I thought was the o-nitrophenole was the p-nitrophenole and the p-nitrophenole is whatever.
The p-nitrophenole got no significant peaks in the nmr other then the solvents and impurities.
Now for the main confusion I can not explain where the o-nitrophenole is.
All vials I took before the first fraction where either non UV-active on a TLC or just resulted in some tar inside the glassware after destilation of the solvent.
The raw product weighted 2.657g and I recovered 495 mg p-nitrophenol (as I now know by the NMR).
I also took an MS but the fraction which i thought was p-nitrophenole was not able to ionize acording to the operator....
What could that product be if I cant see it in the NMR and MS?