Sidmadra - 15-8-2017 at 16:29
I would have posted this in the Organic Chemistry section, but I don't have any references saved at the moment.
I recall reading a few weeks ago about alkoxide salts being able to be synthesized in high yield by using the alkali hydroxide equivalent with the
alcohol, along with molecular sieve to absorb water and drive the reaction forward.
Would it be possible for a similar principle to be applied, in which an aromatic ether or an tertiary aniline compound is deprotonated with lithium
hydroxide and molecular sieves to absorb the water? I know this reaction might be potentially slow, but in theory it should happen even there's even a
little equilibrium. Even though Lithium Hydroxide is significantly weaker than something like butyllithium, the deprotonation equilibrium should be at
least somewhat present, and if this is the case, then this equilibrium could potentially be driven forward with the removal of water.
Can anyone think of a reason why this might not work? At first I figured it is too good to be true, but I also thought making high yield alkoxides
from hydroxide+sieve+alcohol would be too good to be true. Molecular sieves can do some pretty amazing things.
MeshPL - 16-8-2017 at 11:54
There are 2 problems: first the water in molecular sieves is also in eqilibrium with water in whatever solution you do your reaction in. So there will
always be some ready to hydrolyse your lithiated compound.
Secondly, the rate of deprotonation of any benzene derivative you mentioned by mere lithium hydroxide will be extremely low. So low it can be ignored
for most purposes. I don't know how low, but I guess that even if you could magically remove water from the solution continuously and at the moment it
is produced it would take a long time, possibly longer than the age of universe! (That's only my guess though.)
unionised - 16-8-2017 at 12:15
I rather suspect that LiOH will trash the mol sieve.
MeshPL - 17-8-2017 at 14:14
That would be a problem as well as well.