[adhikary]

Usually I prepare deuterated benzylamine [(D₂NCH₂C₆H₄X) X = different substituents, such as 4-MeO, H, 4-Cl etc.)]with the mixture of specified substituted benzylamine and deuterium oxide (1:3 volume) at room temperature with constant stirring for several days (2 to 5 days). Then extract the deuterated benzylamine with diethylether. The ether solution is dried with anhydrous magnesium sulfate for an hour, then filter it (MgSO₄) out and the solution is dried under reduced pressure. But most of the time the conversion rate is over 82% but bellow 90%. I need over 98%. If there any idea available to improve the process please let me know. It will be helpfull for me a lot.

[Dan]

Sounds like a 3:1 D₂O ratio does not give a sufficient H/D ratio then. You probably just need to use more D₂O. I would suggest taking your ~80% D amine and dissolving that in D₂O and repeat the procedure as before. You might need to do a few cycles to reach >98% D.

This may be a stupid question, but are you sure D₂O is >98% D?

[adhikary]

Dear Dan,

I tried for 3/4 cycles and the D₂O, what I used, was 99.9 atom % and produced by Aldrich, USA. I just interested about the process better than this and less time consuming. If available please inform me. Thank you for your commet.

[Honclbrif]

Is it very humid where you are? D₂O is very hygroscopic and will sequester normal H₂O from the atmosphere. If your bottle is old, it may very well no longer be 99.9 atom %.

However, a drop or two (substoichiometric amount) of deuterium chloride may speed things up.

If that that and repeated cycles of deuteration don't do it, you need to consider that any time your amine touches anything that may have traces of water or acid on/in it, you're losing some deuterium. Rigorously dry everything, and think about ways to streamline your process.

[adhikary]

Dear Honclbrif,

Thank you for your valuable comments. The D₂O is new and recenlt purchased. I think your following comment may be effective and I shall try.

However, a drop or two (substoichiometric amount) of deuterium chloride may speed things up.

Thanks again for your comments.