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Author Topic: Separation of Amides and Amines  (Read 590 times)

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Ubongo2142

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Separation of Amides and Amines
« on: January 29, 2019, 04:35:01 AM »

Hello everyone, I have a small problem and I was hoping to find some help here.

I´m starting from 2-amino-1-butanol (2eq) with acryloylchloride (1eq) in tetrahydrofuran to obtain the corresponding amide, while my resulting salt should precipitate with the excess amonibutanol as the hydrochloride. The precipitate was filtered off and THF removed under reduced pressure. In the 1H NMR spectrum however, I still see residual aminobutanol, which is why I wanted to purify my mixture by column chromatography. First attempts with TLC´s weren´t really successfull, either my spots won´t advance along the TLC (tested with mixtures of DCM and MeOH) or they didn´t separate along the way. I tried using small amounts of acetic acid and Et3N, but didn´t see any promising separation along the way with the Et3N. With the Addition of Acetic Acid i can see a Separation of the corresponding spots, but i´m not sure, wether or not the Amide gets hydrolyzed by the dilute acid.

Is there an easy way to separate amides and amines, either with or without column chromatography?

I thank you in advance!
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rolnor

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Re: Separation of Amides and Amines
« Reply #1 on: January 29, 2019, 08:19:14 AM »

You could dissolve the mixture in EtOAc and wash with water, the product amide should be in organic phase, I think.
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wildfyr

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Re: Separation of Amides and Amines
« Reply #2 on: January 29, 2019, 05:40:50 PM »

Do more than 1 acid wash
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Babcock_Hall

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Re: Separation of Amides and Amines
« Reply #3 on: January 30, 2019, 08:31:07 AM »

Is your amide strained or otherwise known to be hydrolytically labile?
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Ubongo2142

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Re: Separation of Amides and Amines
« Reply #4 on: January 30, 2019, 08:51:13 PM »

My amide is not known to be hydrolytically labile. In Fact I´m planning to use the final compound in aquaeous environment.

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Babcock_Hall

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Re: Separation of Amides and Amines
« Reply #5 on: January 31, 2019, 03:09:30 AM »

Breaking peptide bonds completely is performed in 6 M HCl at 110 °C for 24 hours.  What are the conditions of your acid wash?
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kriggy

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Re: Separation of Amides and Amines
« Reply #6 on: February 04, 2019, 12:26:53 AM »

I would try to wash it once or twice with 10% aq. HCl (v/v). Used it multiple times while making amides works like a charm also multiple times with chiral aminoalcohols like phenylglycinol, valinol or prolinol.
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