(a) How will you convert methyl bromide to dimethylamine? (b) How will you prepare propanamine from methyl chloride using suitable reactions?
Here's what I have come up with.
a) While one might expect that it can be accomplished in one step by reacting with methylamine, it would more likely produce a mixture of
Furthermore, it is difficult to control this reaction so that you get to a specific step and stop. So, that isn't the best idea.
However, I actually can't think of any other ideas for this. Since this is probably a theoretical exercise, I guess it's OK to give the following synthesis:
To do this, you may have to increase the pH to be between
You could, however, have a pH above
b) This also asks us to consider reacting amines with alkyl halides. Here's a way to do it without resorting to that.
#"NaH"#would deprotonate acetylene (similar to #"NaNH"_2#), which can then act as a nucleophile in an #"S"_N2#reaction and form methylacetylene.
- Hydroboration adds
#"OH"#onto the less-substituted carbon (anti-Markovnikov) instead of the more-substituted carbon (Markovnikov).
- Keto-enol tautomerization occurs to stabilize the terminal enol into an aldehyde.
- Adding ammonia in trace acid (pH near
#4.5#for optimal activity) forms an imine ( #"R"-"C"="NH"#, in this case). What happens is that the oxygen gets protonated by the two protons transferred from #"NH"_3#, and leaves as #"OH"_2^(+)#when the tetrahedral intermediate collapses to form the imine.
#"H"_2#on #"Pd/C"#reduces the #"C"="N"#bond to a #"C"-"N"#bond, similar to how it works on alkenes.