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Topic: Primary and Secondary Amine  (Read 2733 times)

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Offline Messi

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Primary and Secondary Amine
« on: March 20, 2013, 05:55:02 PM »
Hi guys,

I just did a simple SN2 reaction and added my amine to a carbon. Thing is, I got a mixture of products... I got both the mono and di alkylated amine. I took the TLC and got a few spots. I was wondering which of them corresponded to my primary amine, and which corresponded to my secondary amine! I'm not sure which would be more polar. Knowing which spot is which is important  so I can isolate the primary amine and use it in my next step!

My amine is pent-4-yn-1-amine or the di-alkylated amine. I used 5:1 DCM:MeOH as my eluent system.

Picture shown below:



My amine is pent-4-yn-1-amine or the di-alkylated amine. I used 5:1 DCM:MeOH as my eluent system.
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Offline discodermolide

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Re: Primary and Secondary Amine
« Reply #1 on: March 20, 2013, 10:02:17 PM »
I think you should spot less compound on the plate. The solvent is maybe also too polar, maybe try 10% methanol and use a 20cm plate.
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Offline Messi

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Re: Primary and Secondary Amine
« Reply #2 on: March 20, 2013, 10:16:45 PM »
Quote from: discodermolide on March 20, 2013, 10:02:17 PM
I think you should spot less compound on the plate. The solvent is maybe also too polar, maybe try 10% methanol and use a 20cm plate.

Good idea. However, because I have a mixture of primary, secondary, teritary amines, how will I know which are which on my TLC plate? Which are more polar?

Also, I just rotovapped one of my amines I got... and I left it there quite long... I got a big gumpy solid after... quite interesting.. might be a quaternary salt..
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Offline discodermolide

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Re: Primary and Secondary Amine
« Reply #3 on: March 20, 2013, 10:19:47 PM »
Try and get some simpler alkyl amines and run them on TLC this may give you an indication as to where the secondary run with respect to the primary and tertiary.
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Offline Messi

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Re: Primary and Secondary Amine
« Reply #4 on: March 20, 2013, 10:49:52 PM »
Quote from: discodermolide on March 20, 2013, 10:19:47 PM
Try and get some simpler alkyl amines and run them on TLC this may give you an indication as to where the secondary run with respect to the primary and tertiary.

Unfortunately I don't have access to any alkyl amines :) I guess I will have to do my column and isolate each amine and then run an NMR and look at integrations to see which are which :)
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Offline discodermolide

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Re: Primary and Secondary Amine
« Reply #5 on: March 20, 2013, 10:54:40 PM »
Yep, bite the bullet and run a column.
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Offline Dan

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Re: Primary and Secondary Amine
« Reply #6 on: March 21, 2013, 05:29:08 AM »
I would test triethylamine doping to see if it helps clear up the streaking problem.

http://www.chemicalforums.com/index.php?topic=64624.msg233048#msg233048
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