[stasiu]

What happens, at molecular level, while evaporating an aqueous solution of a base, B if ammonia is present in the same solution?  (pka of conjugated BH+ is say about 10)
So in the solution there is: BH+, OH-, NH4+
What is supposed to be left after the evaporation is a free base B, correct?
Why not a hydroxide BH+OH-(s) or something like this? Or can [BH+OH-] be an intermediate - the last species just before last water is expelled.

(As evaporation goes on most of NH3 is liberated from the solution and pH is dropping. To neutral ??
If it's indeed neutral the base is already protonated, BH+. So we should have BH+ and OH- instead of just B in H2O.)

Comment welcome

[Mitch]

You should be making salts of the bases near the end of the evaporation process.

[stasiu]

Thanks for that hint...
...However, what I am clearly making is a gummy blob, which doesn’t look like a salt to me at all.
And that would be the salt of what by the way? I mean, BH+What-? Unless you meant hydroxide here.
I have nothing else in the solution.

Similarly, when you take water soluble B, dissolve it in pure water, what you have is protonated BH+(aq) and OH-(aq).
When you vac down the water you go back to a free base again, I presume.

Was just wondering if it goes through [hydroxide] or not.


Stasiu

[Borek]

Can you be more specific about B?