Phenylacetone (P2P) synthesis from benzaldehyde with butanone

William Dampier

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Reagents:
  • Benzaldehyde 1000 g;
  • Methyl ethyl ketone (MEK) 1000 ml;
  • Distilled water 14.5 L;
  • Chloroform (CHCl3) 7.6 L;
  • Sodium bicarbonate solution (NaHCO3);
  • Magnesium sulphate (Na2SO4) anhydrous;
  • Glacial acetic acid 10 L;
  • Hydrogen peroxide (H2O2) 1300 g 50 %;
  • Sodium hydroxide (NaOH) 600 g;
Equipment and glassware:
Step 1. 3-Methyl-4-phenyl-3-buten-2-one synthesis (cas 1901-26-4).
1. Benzaldehyde 1000 g and methyl ethyl ketone (MEK) 1000 ml are mixed in 5 L flask, stirred and chilled at 0 °C.
2. HCl gas is bubbled slowly through the mixture for a 1.5 h.
3. The solution is stirred for addition 1.5 h at room temperature.
4. Distilled water 2 L is added. The solution is
extracted with chloroform (CHCl3) 800 ml x2, then the extract is washed with sodium bicarbonate solution (NaHCO3) to neutral pH and dried over magnesium sulphate (MgSO4).
5. Solvent is evaporated
under vacuum and 3-methyl-4-phenyl-3-buten-2-one (cas 1901-26-4) is distilled under vacuum (b.p. 269.6±9.0 °C at 760 mm Hg). Reaction yield is 1000 g.
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Step 2. 2-Acetoxy-1-phenyl-1-propene (cas 24175-87-9) synthesis.
1. 3-Methyl-4-phenyl-3-buten-2-one (cas 1901-26-4) 1 kg from Step 1, glacial acetic acid 10 L and hydrogen peroxide (H2O2) 1300 g 50 % are poured into a 25-30 L batch reactor with reflux condenser, stirred and at 55 °C for 23 h.
2. Next, distilled water 10 L is added.
3. The reaction mixture is
extracted with chloroform 5 L and dried over magnesium sulphate (Na2SO4).
4. Solvent is evaporated
under vacuum. 2-Acetoxy-1-phenyl-1-propene (cas 24175-87-9) yield is 800 g.
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Step 3. 1-Phenyl-2-propanone (P2P; cas 103-79-7).
1. 2-Acetoxy-1-phenyl-1-propene (cas 24175-87-9) 800 g from Step 2 and sodium hydroxide (NaOH) 600 g in distilled water 2500 ml is stirred at 50 °C for 12 h in 10 L flask with reflux condenser.
2. Reaction solution is extracted with chloroform 1000 ml, dried over magnesium sulphate (Na2SO4) and the solvent is evaporated
under vacuum. 1-Phenyl-2-propanone yield is 650 g.
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cyb3r0

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Thank you for the explanation. Please mention the required materials that you knew
benzaldehyde and Methyl Ethyl Ketone ( MEK )
Is this all that is required?
Thank you
 

MadHatter

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Thank you so much for the easy and detailed synth description!
How about the hydrogen peroxide, could that be substituted? It's a really controlled chemical nowadays, and a bitch to synthesize yourself. Its mainly there as a catalyst in the reaction between the glacial acetic acid and the 3-methyl-4-phenyl-3-buten-2-one, right? What could be a good substitute?
 
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Jack

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Its mainly there as a catalyst in the reaction between the glacial acetic acid and the 3-methyl-4-phenyl-3-buten-2-one, right? What could be a good substitute?
It is not a catalyst it is an oxidant please read the link provided, search up baeyer villiger oxidation.
 

MadHatter

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It is not a catalyst it is an oxidant please read the link provided, search up baeyer villiger oxidation.
JackOk, good, an oxidant. And I see the reaction in the link. Thank you! In it they use sodium perborate for the BV- oxidation. That might be more accessible. I guess piranha solution could be used also? What other candidates are there?
 
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MadHatter

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After reading up a bit: how about sodium percarbonate? Would that suffice? Because if it would, this synthesis would become much more OTC. And definately worth the time to calculate the molar ratio.
 

William Dampier

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Approximately 3kg percarbonate for this reaction+water. Find a concentrated peroxide is best choice.
 

MadHatter

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That's perfectly doable. Of course it's second best, but hydrogen peroxide in concentrations above 3% is a strictly controlled substance nowadays in most of EU.
One thought though: wont the carbonate ion react really vividly with the acetic acid? And maybe neutralize it?
 

Jamroz

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Is it necessarliy to make it under vacum destilation or normal pressure destilation will be enought ? Could you expand first step in the reaction hcl gas bubbled in mixture
 

a_king

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is it possible to replace chloroform?
 

MadHatter

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is it possible to replace chloroform?
a_kingWhy would you want to replace chloroform? It's easy to synthesize yourself with acetone and bleach. Check youtube.
But if you really need to for some reason, dichloromethane and chloroform are usually interchangeable.
 

MadHatter

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BTW, why such ENORMOUS quantities of GAA and H2O2? Is it possible to use less? What are their roles in this reaction?
 
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MadHatter

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I guess what I'm really wondering about is the stochiometry of this reaction. In other write-ups of the bayer-williger I can't seem to find this enormous amounts of GAA. Can somebody help me with the rationale? I'm really close to trying this one out, but the amount of GAA is problematic.
 
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