[Jfalken]

Hi!

So, in a reaction, where you'd need pyridine as a trapping agent - are there any pros/cons to use pyridine as the solvent itself (cost aside) or would it be more beneficial to use an organic solvent and then add as many moles pyridine as you'd need to form the trap?

Let me know your thoughts.

[Babcock_Hall]

My first thought is that one has to decide this on a case-by-case basis.  There are some reactions in which pyridine is thought to be a nucleophilic catalyst.  Are you following a specific protocol?

[Jfalken]

My first thought is that one has to decide this on a case-by-case basis.  There are some reactions in which pyridine is thought to be a nucleophilic catalyst.  Are you following a specific protocol?

Not following a specific protocol, just a general question on how to understand the reaction equation.
So usually it is stated something like this:

                        reagent
Starting material  ----->   Product 
                        solvent

But when the solvent is pyridine, and you know you need a proton trap, is it still valid to assume that pyridine should be the solvent if a reagent is given above the arrow?
I know pyridine can be used as a solvent itself, but in some reaction, its primary use is as a proton trap (from what I understand).

[clarkstill]

It stinks, it can sometimes be tricky to remove all of it by evaporation alone. Often you need to do an acid or CuSO4 wash to remove all traces (not that this is a massive problem). But I suppose you might worry a bit more than with other solvents - a little trace DCM is unlikely to affect any subsequent reactions, but some trace pyridine could mess with things (e.g. if you're using a catalytic acid).

That said, pyridine isnt an uncommon solvent by any stretch. Typically alcohol acylations would be done using Ac2O/pyridine as both the solvent and reagents.

[Babcock_Hall]

Going on memory, but I seem to recall making (tBuO)₂P(O)H from PCl₃ and tertiary-butanol in pyridine as the solvent.  I seem to recall using a small volume of toluene to strip away pyridine that remained after the first rotary evaporation step, in a second evaporation.  This is one of several times that toluene has come in handy in this way--it also helps to remove hexamethyldisilazane.  In acylation reactions such as this one, pyridine might be acting as a nucleophilic catalyst.

[OrganicDan96]

i have recently been converting amides to nitriles uspin TFAA with pyridine as the solvent. the procedure called for a wash with potassium bisulphate after evaporating the pyridine, we didn't have any so evaporating with toluene after the first evaporation worked a treat.

[wildfyr]

Aqueous Copper sulfate extraction should be the only pyridine removal method needed