[matman27]

Hello Everyone,

A friend needs some 15N labeled ethylamine.  It is extremely expensive, so we are going to synthesize it.  He has a tank of 15N anhydrous ammonia, so I was thinking reduction amination on acetaldehyde.  Does anyone have any ideas or pointers for the synthetic procedure or handling.  I was planning a fractional distillation and then gas transfer to another tank for isolation.  I think an extractive workup needs to be avoided because the boiling point is 16 deg C.  Otherwise, would a substitution with ethylbromide/iodide be easier?


Thanks,

-Matt

[OC pro]

I had a similar problem just recently where I needed Ethylamine-d5, which is also quite expensive. You could synthesize 15N-phthalimide out of 15N-ammonia and alkylate it with ethylbromide. Then one can release the ethylamine and isolate it as the corresponding hydrochloride (handling it as the free amine is very difficult, this stuff is highly flammable). It was described somewhere in the literature.

[BobfromNC]

The reductive amination might be difficult just due to the close BP of acetaldehyde  (21 C) and the product.   You might be better off to do a simple alkylation of the ammonia with the ethyl iodide (bp ~70 C) as that would ensure allow you to distill the ethylamine from the reaction.  You might get some di/tri alkylation, but that would be reduced by using excess ammonia, which is likely your more expensive reagent. 

If you do the reductive alklyation, you would also need excess ammonia to prevent further overalkylation.    Depending on the next step, you could react the ammonia with acetyl chloride making the N15-acetamide (note Aldrich sells this for $300/gram), which would be easier to isolate, then reduce with Borane or LAH to the amine, which could be then distilled easily from the rest of the muck, and then isolated as the free amine or reacted with HCl to store it.

Bob