Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Optimist on December 30, 2016, 07:48:54 AM
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I want to purify given compound by HPLC, But I am not sure whether this molecule show absorbance in UV region. In my HPLC system we usually use two wavelength (220nm, and 254nm) for measuring absorbance during purification of compound by preparative HPLC>
Can some please throw light on the absorbance of molecule in UV using HPLC. what are the criteria other than, extensive conjugation and benzene right.
thanks in advance.
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It can be easily found in many handbooks.
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It can be easily found in many handbooks.
Can you please name any handbook? It would be highly appreciated.
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All chemistry students know Silverstein - Spectrometric Identification of Organic Compounds
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I hope you use a acidic mobilephase, the aminogroup could react with with the estergroups. Do you handle the compound as some kind of aminehydrochloride or other form of salt?
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I hope you use a acidic mobilephase, the aminogroup could react with with the estergroups. Do you handle the compound as some kind of aminehydrochloride or other form of salt?
The stability is not an issue, The compound is stable, so no worries about stability. I actually want to purify this compound on C18 column using water and ACN as mobile phase. I just want to confirm about the UV absorbance of this compound ( free amine not HCl salt) under the given wavelength.
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Carbonyls have a UV absorption due to both pi-pi* and n-pi* transitions, and these are generally in the neighborhood of 190 or so nm and 270 or so nm respectively for a basic ketone. Your molecule will be a bit different, but even so I suspect it will show some absorbance with your instrument. Nevertheless you'd be best off measuring a UV-Vis spectrum of your molecule (or something similar) to be sure where the UV-Vis absorption maxima are, rather than proceeding blindly.
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If its not visible in UV, you can protect the aminogroup with fmoc to make it visible in UV/VIS. It adds two more steps but might be worth it
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If its not visible in UV, you can protect the aminogroup with fmoc to make it visible in UV/VIS. It adds two more steps but might be worth it
I already deprotected amine (Cbz group) using C/Pd-H2.
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Carbonyls have a UV absorption due to both pi-pi* and n-pi* transitions, and these are generally in the neighborhood of 190 or so nm and 270 or so nm respectively for a basic ketone. Your molecule will be a bit different, but even so I suspect it will show some absorbance with your instrument. Nevertheless you'd be best off measuring a UV-Vis spectrum of your molecule (or something similar) to be sure where the UV-Vis absorption maxima are, rather than proceeding blindly.
I performed the HPLC analysis using dual wavelength (220 &250nm) but it show less absorbance but I am not sure whether this is my compound or impurities.
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MS not showing anything?
Im not sure how difficult is to make your compound (ie. if you can spare anything) but maybe you can try to run the prep HPLC with just a small amount just to isolate few mgs and then run NMR to confirm if its the product or not
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Strong UV signals are due to conjugation, which does not exist in the given molecule. As consequence, there are two options:
1). Either you take a UV spectrum (in the same solvent as used in HPLC, in not being aqueous) of the given compound and see if the strongest absorption band is strong enough for UV detection.
2). Or, you use a refractive index detector.