[salteen]

Hi folks,

Anyone here have experience removing a sizeable amount of n-butanol from a product, either through roto-vaping or some other means?  I'm trying to form a butyl ester from a benzoic acid derivative and have been getting poor yields so far with the coupling agents I've tried.  I'm now tempted to try a simple Fischer esterification with H2SO4 in butanol, so long as I can remove the excess butanol afterwards....

We have a rotovap hooked up to a Welch pump which is capable of removing DMF (although slowly).  I suspect it would do the same with butanol, but wanted to see if anyone has past experience trying this.

[Babcock_Hall]

No direct experience, but n-butanol boils at 118 °C.  That is somewhat less than DMF.

[opsomath]

Wikipedia suggests that it azeotropes off with water. Perhaps you can Fischer esterify, neutralize, then steam distill off the butanol, ending with a suspension of your ester in mostly pure water?

Alternatively, there's a toluene azeotrope as well.

[Adamcp898]

Easiest thing would be to try find an extraction solvent to wash your product out with, something like ethyl acetate may work. Or else seeing if any solvents (perhaps ethers) can force precipiate your product.

Other than that you're left with azeotroping the butanol as others have suggested. Water is indeed one but you probably will need a lot of it iirc.

[salteen]

I went ahead and tried azeoptroping it off with toluene.  Took a couple hours, but worked in the end!  Thanks for the suggestions.

[opsomath]

Aw yeah.

[BobfromNC]

If you use a rotovap and heat it up to 60C, n-butanol and higher alcohols up to n-hexanol will come off if you let them go a while, I just made some esters that way.   It just takes, heat, a good vacuum, and time.

[Babcock_Hall]

We'll keep that in mind.  We just used n-butanol as a recrystallization solvent last week.