deadpool
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ethyl acetoacetate synthesis
Hello fellow chem nerds its deadpool again. I've been busy with movies, but I thought I would try a synthesis of ethyl acetoacetate. Unfortunately I
haven't had much luck. The basic idea was to try claisen condensation using a solution of sodium ethoxide and ethyl acetate. I don't have sodium
metal so I used sodium hydroxide and Everclear, filtered it on the frit and used the solution (lightly brown). I know the extra ethanol will hinder
the reaction but I figured I could slowly distill off the ethanol to drive the reaction forward. Unfortunately it looks like ethyl acetate and
ethanol have nearly identical boiling points so during the distillation i'm likely removing both. I figured if I was successful at making any ethyl
acetoacetate it would remain do to it having an extreme high boiling point. Once most of the distillate is removed crystals typically form in the
flask. I was wondering could this be a sodium salt of ethyl acetoacetate? At this point I wasn't sure what products could remain or how to identify
them I guess. I saw UC325 synthesis on youtube looks like he had quite a bit of trouble as well... any pointers or success stories with this?
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Boffis
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I suggest you look at the Organic Reactions Vol 1 page 263 onwards. Its in the SM library. This is a reveiw of the Claisen condensation reaction and
explains that it is a series of equilibria that favors the original ester unless the final beta ketoester can be converted into the sodium salt. I
suspect that water in the reaction mixture generated from the sodium hydroxide alcohol reaction will prevent this final process and so favor the
original ester. This may be why they always use sodium in dry ethanol to generate the alkoxide when the reaction is described in text books like Vogel
etc. Recently reading papers on the modern take on this reaction has provided examples where sodium hydride is used to great effect giving much better
yields.
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CuReUS
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NaNH2 on ethylacetate gives ethylacetoacetate. Maybe the same reaction could be done using LiNH2 ?
see erowid's birch reductions to make LiNH2. As you know Li can be extracted from batteries.
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karlos³
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Instead of using Lithium amide, if one considers the availability of Lithium metal, it would be much easier to prepare a lithium alkoxide from it and
to use this instead of sodium alkoxide.
Did you use thin layer chromatography to follow your reaction progress?
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deadpool
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Great info!!
I posted the questions as I finished the distillation last night and haven't done anything else with it yet. I am quite please with the help and
suggestions on this forum. Thin layer chromatography is an excellent idea, I have to means to do so just haven't attempted it at home lab yet. If
your curious to how this can be done cheaply at home checkout TheHomeScientist youtube channel for making TLC plates. It will probably take me quite
awhile to get that down however. Using Lithium from batteries is an awesome idea! Should have thought of it myself >.< Thanks! Also very
curious about the sodium amide method as I can produce this as well albeit more laborious task (rather make the azide i think). The remaining
product in the flask is very minute so Boffis is right that the reaction favored the ethanol despite being removed via distillation. Thanks guys for
the help round 2 ding* I'll let you guys know how it turns out.
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clearly_not_atara
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Orgsyn uses sodium in ethyl acetate with no ethanol or ethoxide added to the reaction. At the bottom it mentions that dry sodium ethoxide can
perform the reaction, and that when using NaOEt, the reaction proceeds most efficiently when ethanol is removed from the rxn mixture as it proceeds:
http://www.orgsyn.org/demo.aspx?prep=CV1P0235
It appears that ethanol inhibits the reaction. I think that CuReUS has got the right idea, although the direct reaction of lithium with ammonia may be
tricky. Ethylamine is significantly more convenient to handle (since it can be cooled with water ice), less hygoroscopic and will form EtNHLi which is
probably just as good for the condensation (also better solubility properties).
However, the nature of lithium-ammonia solutions is not quite accurately represented by "LiNH2". The reactions:
Li + 6 NH3 >> Li(NH3)6+ + e-
Li + 4 EtNH2 >> Li(EtNH3)4 + e-
do not generate lithium amide. That is formed only after the solution decomposes:
Li(NH3)6 + e- >> LiNH2 + 5NH3 + H2
It can actually take more than a week for a Birch solution to decompose. Electride itself will probably cause many side-reactions (particularly
Bouveault-Blanc-like reactions) making it undesirable.
The question is, how to decompose a Birch solution to a solution of lithium amide? UV?
[Edited on 15-3-2016 by clearly_not_atara]
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CuReUS
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Quote: Originally posted by clearly_not_atara  |
It can actually take more than a week for a Birch solution to decompose. Electride itself will probably cause many side-reactions (particularly
Bouveault-Blanc-like reactions) making it undesirable.
The question is, how to decompose a Birch solution to a solution of lithium amide? UV?
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yes atara , you are right. the birch reaction method will not give LiNH2. according to wiki,its made by dissolving Li in NH3 in
the presence of Ferric nitrate as catalyst
https://en.wikipedia.org/wiki/Sodium_amide#Preparation_and_s...
another method is by reacting Li with NH3 gas
http://www.orgsyn.org/demo.aspx?prep=cv3p0778
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