1-Phenyl-2-propanone (P2P) synthesis from Diethyl(phenylacetyl)malonate

G.Patton

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Introduction

This is one of the simplest ways to obtain 1-Phenyl-2-propanone (P2P). Diethyl(phenylacetyl)malonate can be bought in some web market quite easy or synthesized by yourself using this method. Also, you can learn other P2P synthetic paths in our forum by following links: Synthesis of P2P from benzaldehyde with MEK, Synthesis of P2P by oxidation of alpha-methylstyrene with Oxone, Phenylacetone (P2P) syntheses via Grignard reagents, Industrial phenylacetone (P2P) production from benzene, Synthesis of P2P from P2NP with NaBH4 via K2CO3/H2O2 system.

Difficulty Rating: 3/10
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Equipment and glassware: 96HPpoRuJa

Reagents:

  • Phenylacetylmalonate (1) 48.5 mL (55.66 g, 0.20 mole) [Diethyl(phenylacetyl)malonate; cas 20320-59-6];
  • Glacial acetic acid (AcOH) 60 mL;
  • Concentrated sulfuric acid (H2SO4) 7.5 mL;
  • Distilled water ~240 mL;
  • Sodium hydroxide (NaOH) solution 20 % ~100 mL;
  • Diethyl ether (Et2O) ~150 mL;
  • Sodium sulfate (Na2SO4) anhydrous ~100 g;
  • Drierite ~50 g (optional).

Procedure

To a diethyl phenylacetylmalonate (1) 48.5 mL (55.66 g, 0.20 mole) was added a solution of 60 mL of glacial acetic acid, 7.5 mL of concentrated sulfuric acid and 40 mL of water, and the mixture refluxed in 500 mL round bottom flask with reflux condenser for four or five hours until the decarboxylation was complete. The reaction mixture was chilled in an ice-bath, made alkaline with 20 % sodium hydroxide solution, and extracted in a separatory funnel with several portions of ether (~3 x 50 mL). The combined ethereal extracts were washed with water (~200 mL), dried with anhydrous sodium sulfate (Na2SO4) followed by Drierite (optional), and the solvent distilled off. The residue containing the ketone (2) was distilled in vacuo to give 1-Phenyl-2-Propanone (2) in 71 % yield (b.p. 97-98.5 °C/13 mmHg, 214-215 °C/760mmHg).
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An Alternative Diethyl(phenylacetyl)malonate Hydrolysis to BMK and PAA (phenylacetone and phenylacetic acid)

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This is an alternative synthesis method which is allow to get Phenylacetone (P2P) from Diethyl(phenylacetyl)malonate. This method consist of Diethyl(phenylacetyl)malonate alkaline hydrolysis into Phenylacetyl-malonic acid sodium salt with subsequent hydrolysis by cheap and easy available hydrochloric acid. In addition, this synthesis way takes less equipment and produce height quality product.

Equipment and glassware:

  • 5L Three necked round bottom flask or batch chemical reactor;
  • Top stirrer;
  • Reflux condenser;
  • Retort stand and clamp for securing apparatus;
  • 1L Separatory funnel;
  • Water bath and ice;
  • 1000mL x2; 500mL x2; 250mL x2 Beakers;
  • pH indicator paper;
  • Laboratory scale (0.01-100 g is suitable);
  • Measuring cylinder 100mL and 1000mL;
  • Heating plate;
  • Filter paper;
  • Funnel;
  • Frige;
  • Glass rod;

Reagents:

  • Diethyl(phenylacetyl)malonate 800g (cas 20320-59-6);
  • Sodium hydroxide (NaOH) 230g;
  • Distilled water 1230 ml;
  • Hydrochloric acid (HCl aq);

Phenylacetyl-malonic Acid Sodium Salt From Diethyl(phenylacetyl)malonate
1. An alkali aqueous solution 50% is prepared in advance so that it has time to cool down. Sodium hydroxide 230g (NaOH) is dissolved in water 230g and cooled down to room temperature.
2. The cooled NaOH aqueous solution of is poured into a dropping funnel and this funnel is installed onto a reactor.
3. Diethyl(phenylacetyl)malonate 800g is poured into the reactor. The reaction is carried out at room temperature but a forced cooling have to be used during the hydrolysis.
4. A stirrer is turned on and cold (2-4°С) NaOH aq solution adding to the cold reaction mixture is begun slowly. The mixture is stirred for 12h. Reaction temperature has to be controlled (the mixture is self-heated). As the solution is added, reaction mixture (RM) color is changed and thickened until it is become completely thick and lumpy. The lumps is broken into a homogeneous mass.
5. RM is moved from the reactor to a vacuum filtration system funnel and filtered. Phenylacetyl-malonic acid sodium salt is obtained.
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Phenylacetic Acid and Phenylacetone (P2P) synthesis from Phenylacetyl-malonic Acid Sodium Salt

6. Phenylacetyl-malonic acid sodium salt from the previous step is placed into the reactor and water 1L is added.
7. A reactor jacket is heated up to 60-65°С during a constant stirring. Phenylacetyl-malonic acid sodium salt has to be completely dissolved.
8. After complete dissolution, hydrochloric acid (HCl aq) is added until <3 pH. Reaction mixture is heated 60-80°С and stirred.
9. After about one hour, the phenylacetyl-malonic acid sodium salt hydrolysis is complete. The stirrer and heater are turned off. Layers are separated.
10. While the mixture is still hot, the bottom water layer is drained out and discarded. Layers can be separated by separatory funnel. The top layer is collected.
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Phenylacetic Acid and Phenylacetone Separation

11. During the top layer cooling in a fridge, phenylacetic acid is crystallized. The yield is about 400g of the mixture.
12. After separation by decantation, 200g of phenylacetic acid and 200g of phenylacetone (yield is 52%) are obtained. A phenylacetone (P2P) purity is quite good for further synthesis without additional purification.
 
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btcboss2022

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I made this process with success!
We are just trying to fix a small problem with salt precipitate in the alkalination phase.
I'm very grateful to G.Patton for all his help great expert thanks again.
 

hello999

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Perform CAS 20320-59-6 official procedure After 4 hours of reaction at 80°C, stop heating, then adjust the alkali pH with sodium hydroxide, until 7, it can't go up, stratification appears, the oil layer is on top, and then ether extraction is added, and the stratification begins, and the ether layer is extracted, and the upper layer starts, and the distillation at atmospheric pressure at 220° keeps going up, and the temperature keeps it at 110°, and a lot of liquid is distilled, and I think it's ether, and then it starts to appear, and this phenomenon in the flask I thought it would be 216° distillation to produce P2P, but there is no problem How can I remedy it
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hacke8

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Hello, have you solved the problem that you can't get 12 on PH? I also encountered the same problem. Please help me. Thank you.
 

btcboss2022

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We are practically sure that the precipitate is Sodium acetate salt from the acetic acid, any idea to avoid it or solve it?
Because in big scale would be a problem.
Thanks.
 

G.Patton

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It could be NaSO4 as well. The best solubility in water has MgSO4. If you have MgOH2, you can try to substitute NaOH.
MgSO4 has 35,1 g/100ml at 20deg
Na2SO4 has 19,2 g/100 ml at 20
K2SO4 has 11.1 g/100 ml at 20
 
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btcboss2022

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Ok we will try it and update you, anyway there is another problem the oil yield is very low and I think I know why could be:

In reflux step must be an intermediary product that boils around 75-80C so the mixture don't goes up this temp, if you heat more you will lose product by the condenser.
Acetic acid boils at 118C
Water at 100C
20320 at 120C
Sulphuric at 337C
So only an intermediary product can be boiling and refluxing at this temp, in my opinion this low temp don't allow to make the reaction properly for this reason the low yield.
We are thinking changes to improve that but is hard to believe that with this exactly method you can get 71% yield for the reasons explained before.
Thanks.
 

btcboss2022

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Hello,

Any idea to change something to allow more temp in the reaction? We need a mixture that don't create an intermediate product of low boiling temp.
Thanks.
 

btcboss2022

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Ok in all the test I have done sometimes the mixture turns yellowish transparent in one single layer:
And sometimes it get yellowish but not transparent and it has 2 different layers.
Is very strange because nothing different or changed in them.
What is sure is that 20320 in the mixture creates an intermediate product that is Ethyl acetate, this product has a low boiling temp and don't allow the mixture to get more than 80C we are thinking to distill it but not easy to choose in what moment exactly do it because it possibly helps in the reaction in some moments.
Another sure thing is that 20320 turns solid when it turns alkali over 8-9ph so because in the basification step , this solid can be solved in acid again if it appears, is totally different to the solid that appears after add alkali.
We will continue making tests and changes to improve it.
Thanks,
 

SpeeD

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Can simple vacuum distillation be used instead of vacuum distillation?
 

G.Patton

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Do you understand your question? :unsure: Do you mean simple distillation instead of vacuum one? You can, 216 deg C is boiling point at normal conditions.
 

SpeeD

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Can simple distillation+vacuum replace a rotary evaporator?
 
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G.Patton

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Yes, it can. Processes are same.
 

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Hi,

COuld anybody answer some doubts?

1.- the alkalinization with NaOH 20%, which is the ph target?
2.- For the extraccion, could I use dichloromethane instead of diethyl ether?
3.- Which layer do I have to extract with several portions of ether (~3 x 50 mL)?
4.- What is "The combined ethereal extracts" refers to?
 

G.Patton

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Hello, alkaline is pH 12
I think yes
Layer with P2P (oily)
(~3 x 50 mL)? - Each portion of sequential extraction 50 + 50 + 50 mL are combined. Read about Extraction in Lab FAQ section.
 

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Costa

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Thanks! just one more... concerning question 3 (extraction with ether), how is it made? I mean, I have to take off the oily layer (with P2P) and add the ether to the other layer in order to extract from there the interesting compound (P2P), is that correct?
 

G.Patton

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>>>Read about Extraction in Lab FAQ section.
Just add solvent to the reaction mass as described in manual and carry out the extraction.
 

Zetetic

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What are the replacement options?
  • Glacial acetic acid (AcOH) 60 mL;
  • Concentrated sulfuric acid (H2SO4) 7.5 mL;
  • Diethyl ether (Et2O) ~150 mL;
In stock:
acetic acid 70%

hydrochloric acid aqueous solution:
Compound
water, inhibited hydrochloric acid 5% or more, but less than 15%, non-ionic surfactants < 5%.

Isopropyl alcohol
Petroleum ether
Dichloroethane
Benzene
Toluene
Methylamine 38%

Any help please!?
 
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Zetetic

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Ha-ha-h...
I seem to have a more serious problem.
Diethyl 2-phenylmalonate is sold, not Diethyl(phenylacetyl)malonate.
:-(
 
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