Boffis
International Hazard
Posts: 1897
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
Furfurylidene acetone
Has anyone any experience of the reaction of acetone and furfuraldehyde? I tried to produce furfurylideneacetone today by mixing a little freshly
distilled crude furfural with a 3 molar excess of acetone and adding dilute sodium hydroxide in methanol-water mixture (to improve miscibility) to the
room temperature mixture. Before I had even added a tenth of the caustic solution the mixture became so hot that the acetone began to boil off and the
mixture became very hot and dark brown. On cooling no solid product formed only a brown, water immiscible liquid.
Clearly furfural is much more reactive than benzaldehyde but the sudden heating seams to destroy the furfural.
Does anyone have a ref to a preparation? or have any proctical experience?
|
|
|
DraconicAcid
International Hazard
Posts: 4412
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
I haven't tried that exact reaction, but keeping the reaction mixture cold is recommended for all the aldol condensations I've tried. It works nicely
with benzaldehyde, p-anisaldehyde, and cuminaldehyde.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
bnull
National Hazard
Posts: 596
Registered: 15-1-2024
Location: Home
Member Is Offline
Mood: Sneezing like there's no tomorrow. Stupid cat allergy.
|
|
Try solid Ca(OH)2 or Mg(OH)2, or even MgO, in place of sodium hydroxide.
|
|
|
Dr.Bob
International Hazard
Posts: 2816
Registered: 26-1-2011
Location: USA - NC
Member Is Offline
Mood: Mildly disgruntled scientist
|
|
Try adding the furfural slower or dropwise. As well as cooling the reaction.
|
|
|
clearly_not_atara
International Hazard
Posts: 2825
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
| Quote: | | Has anyone any experience of the reaction of acetone and furfuraldehyde? I tried to produce furfurylideneacetone today by mixing a little freshly
distilled crude furfural with a 3 molar excess of acetone and adding dilute sodium hydroxide in methanol-water mixture (to improve miscibility) to the
room temperature mixture. Before I had even added a tenth of the caustic solution the mixture became so hot that the acetone began to boil off and the
mixture became very hot and dark brown. On cooling no solid product formed only a brown, water immiscible liquid. |
IIRC furfural forms more stable imines than benzaldehyde. I think this means that the furan ring is more electron-withdrawing than a benzene ring.
That would account for a higher rxn temperature.
I think the usual trick here would be to add more of an inert solvent, like acetonitrile, THF, dioxolane, DMF, EtOAc (may react with NaOH
unfortunately) to keep the reaction cool. Unfortunately it probably has to be aprotic and not acetone, and it's better if it's polar.
|
|
|
DraconicAcid
International Hazard
Posts: 4412
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
Quote: Originally posted by clearly_not_atara  | | Quote: | | Has anyone any experience of the reaction of acetone and furfuraldehyde? I tried to produce furfurylideneacetone today by mixing a little freshly
distilled crude furfural with a 3 molar excess of acetone and adding dilute sodium hydroxide in methanol-water mixture (to improve miscibility) to the
room temperature mixture. Before I had even added a tenth of the caustic solution the mixture became so hot that the acetone began to boil off and the
mixture became very hot and dark brown. On cooling no solid product formed only a brown, water immiscible liquid. |
IIRC furfural forms more stable imines than benzaldehyde. I think this means that the furan ring is more electron-withdrawing than a benzene ring.
That would account for a higher rxn temperature.
I think the usual trick here would be to add more of an inert solvent, like acetonitrile, THF, dioxolane, DMF, EtOAc (may react with NaOH
unfortunately) to keep the reaction cool. Unfortunately it probably has to be aprotic and not acetone, and it's better if it's polar.
|
Ethanol is a suitable solvent for this reaction, surely.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
clearly_not_atara
International Hazard
Posts: 2825
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
^I was concerned about conjugate addition of the alkoxide to the alkene. But come to think of it isopropanol will not be deprotonated by NaOH.
|
|
|
Boffis
International Hazard
Posts: 1897
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
Two more "failed" attempts to produce furfurylidene acetone with different conditions /alkalis also resulted in a deep brownish yellow oil so I went
back to the original paper Claisen & Ponder, J.L. Annalen d. Chem., 1884, pp137-148.
Funny isn't how a little time in the library can save hours of frustration! Apparently the desired compound melts at 37-38 C even after vacuum
distillation and separates initially as a liquid. So it would appear that the reaction did infact work but I was expecting a solid product. Bugger!
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
