Hello everyone,
for my research project, I am doing synthesis with polymer (PEG) and I confirm the formation of the product via NMR. But for me, I don't really trust NMR and it cannot confirm me the formation of my product based on:
- esterification of PEG-OH with acid compound (step 1)
- imine formation (schiff base reaction-step 2)
So I tried to do FT-IR to see the peaks of COO and C=N in my second product. And it is still unclear for me. My spectrum are really strange.
For the formation of imine (step 2) I see the shift in NMR, characteristic to the formation of CH=N (literature) but for me I need more data to confirm it.
Furthermore, I have some additional peaks (not supposed to be here) with high content of protons. So I think my product is not pure....
So I have 3 questions:
1) in FT-IR, how can I confirm the conjugation of OH and COOH (ester) in my synthesis 1
2) in FT-IR, how can I confirm the C=N bond (synthesis 2)
2) For impurities in NMR, what are the options to remove it ?
Thanks in advance
- You can try re-dissolving your sample in a different solvent to see if the impurities are solvent-dependent.
- You can try using a different purification method, such as column chromatography or recrystallization.
- If the impurities are water-soluble, you can try washing your sample with water to remove them.
- If the impurities are volatile, you can try evaporating your sample under reduced pressure to remove them.
- If all else fails, you can try repeating the synthesis and purification steps to obtain a purer sample.
1)answer 1: first time, please obtained FT-IR of the monomer (which monomer of your obtained polymer), and then In FT-IR, the presence of a peak around 1700-1750 cm-1 can indicate the formation of an ester bond. This peak corresponds to the carbonyl stretching vibration of the C=O bond in the ester group. Additionally, you can also look for a peak around 1100-1050-1100-1300 cm-1, which corresponds to the C-O-C stretching vibration in the ester group.
2)n FT-IR, the presence of a peak around 1600-1700 cm-1 can indicate the formation of a C=N bond, carbonyl bond. This peak corresponds to the stretching vibration of the C=N bond in the imine group. Additionally, you can also look for a peak around 3300-3500 cm-1 screeching and Overton of this, 1400- 1500- 1450 cm-1, which corresponds to the N-H stretching vibration in the imine group.
- You can try re-dissolving your sample in a different solvent to see if the impurities are solvent-dependent.
- You can try using a different purification method, such as column chromatography or recrystallization. or other solvent and please check your compound is dry.
- If the impurities are water-soluble, you can try washing your sample with water to remove them. please dry your sample
- cheek resolved and precipitate 3 times.
- If you can not answer about purification
- please check your monomer or the first material you used that
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