Johnny Windchimes - 3-6-2019 at 12:57
Hello again all,
My current project is synthesizing the diketone Benzoylacetone (1-Phenyl-1,3-Butanedione) via Acetophenone.
There are a lot of great and well explored sources for these reactions, not least of all the informative and well researched Hauser et al. paper as
well as more classic examples re: Cumming et al 1937.
(Please see attached references)
So, my question is this:
Dry Sodium Ethoxide. How dry is dry?
Most (I like to call 'classic') documentation involves streams of dry hydrogen gas to effect absolute anhydrous conditions when synthesizing the
sodium ethoxide from Sodium Metal and Anhydrous Ethanol, but I am fairly confident this is not absolutely required for my chosen synthesis (at perhaps
a yield loss).
Would using a smaller excess of Ethanol during the sodium ethoxide production and using a vacuum desiccator be enough to dry it out?
Thanks for your time everyone~
References cited:
Cumming et al, 1937 Pg 509 - Sodium Ethylate aka Sodium Ethoxide Preparation
Hauser et al, Lots of good stuff for Benzoylacetone Synthesis
Prep-Chem Synthesis of Benzoylacetone, which is basically just a verbatim copy of the above 2 authors, but a bit more succinct for a casual glance.
*It seems the entire Cumming et al. book is like 24 megabytes so I cant upload it, however, its easily found on http://www.sci-hub.tw/ by searching for "Systematic Organic Chemistry Modern Methods of Preparation and Estimation"
**I have included just page 509 that relates to sodium ethoxide in lieu of the entire aforementioned document
Attachment: pg 509 - Copy.pdf (226kB)
This file has been downloaded 263 times
Attachment: hauser2011 - Copy.pdf (7.1MB)
This file has been downloaded 385 times
Attachment: Benzoylacetone Classic Synthesis - Copy.pdf (353kB)
This file has been downloaded 632 times
[Edited on 3-6-2019 by Johnny Windchimes]
DavidJR - 3-6-2019 at 16:29
I would just dry the ethanol thoroughly over molecular sieves 3A. I don't think the hydrogen is necessary.
Tsjerk - 3-6-2019 at 23:39
Sodium ethoxide dry in which sense? It is anhydrous per definition, as it reacts with water, but to keep water out of your reaction a drying tube with
CaCl2 should be fine. A little bit of NaOH (from water and ethoxide) should not hurt your reaction too much, you could use a little more sodium or a
little less acetophenone if you think your ethanol is not completely dry.
In the prepchem synthesis, ethyl acetate is the solvent. Reacting the sodium with ethanol and pulling of the ethanol with a vacuum before adding the
ethyl acetate should work fine. Just dry your ethanol with 3A sieves.
Johnny Windchimes - 4-6-2019 at 08:22
It has just now occurred to me that the aforementioned papers could have meant DRY literally as opposed to in the almost universal "water free
reagent" context....
....as in.....make sure the puddle of excess ethanol alcohol has been distilled / evaporated off before proceeding.
I'm leaning more towards this conclusion as I re-read everything again.