How will you convert methyl bromide to dimethylamine?

1 Answer
Sep 10, 2016

#2H_3C-Br + NH_4Br + 3N(CH_2CH_3)_3rarr(H_3C)_2NH + 3[HBr*N(CH_2CH)_3]#


Possibly there would be a laboratory synthesis along these lines. I assume you are answering a problem, and not doing an actual synthesis. The industrial process takes ammonia, methanol, and heat and pressure:

#NH_3 + 2CH_3OH rarr HN(CH_3)_2 + 2H_2O#

But this is not a reaction that you could reproduce in a laboratory.

In the first reaction, each #N-C# bond is formed with the elimination of triethylamine hydrobromide. Hence we need 2 equiv of #Et_3N# for the #2xxC-N# bond formation, and a third equiv to give the ammonia, the free base. The trithylamine operates as a non-nucleophilic base here to sop up the hydrogen bromide produced. These days, we have non-nucleophilic bases such as #"DBU"#, and #"DABCO"#; these are more basic than the amine, and are a lot less pfaff to use.