This phenylacetone synthesis (P2P) approach is a simple way to obtain phenylacetone from BMK ethyl glycidate and its synthesis from benzaldehyde. PMK ethyl glycidate can be hydrolyzed to P2P. This reaction is not water sensitive like the synthesis of BMK methyl glycidate. There are advantages such as a fairly high conversion yield (82% of benzaldehyde to P2P). In addition, the reaction does not require any elaborate equipment and can be easily scaled up.
Equipment and glassware:
- 3 L round-bottomed, four-necked, 3 L round-bottomed reaction flask equipped with reflux condenser, overhead stirrer and 250 mL balanced pressure dropping funnel.
- Funnel
- Retort holder and clamp for securing the apparatus
- pH indicator paper
- Water/oil bath
- Retort stand and clamp to secure the apparatus
- Lab grade thermometer (up to 10 - 100 °С)
- Glass rod
- Silicone hoses
- Measuring cylinders for 100 mL and 1 L
- Laboratory balance (1-200 g is suitable)
- Glass rod
- Beakers 3 L; 1 L x2; 500 mL x2
- 2 L separatory funnel
- Dimethylformamide 900 ml
- Benzaldehyde 300 ml
- Ethyl 2-chloropropionate 540 g
- Benzyltriethylammonium chloride (TEBAC) 32 g
- Potassium carbonate 780 g
- Sodium hydroxide (NaOH) 135 g
- Distilled water ~1.9 L
- Concentrated aqueous hydrochloric acid (HCl) (37%) ~250 mL
Synthesis of BMK ethyl glycidate from benzaldehyde.
1. 900 ml of dimethylformamide is poured into a 3-liter four-neck round-bottom reaction flask equipped with a reflux condenser, a top stirrer and a dropping funnel.
2. Then 300 ml of benzaldehyde is added. An upper stirrer is switched on.
3. 540 g of ethyl 2-chloropropionate are poured into the reactor. 32 g of benzyltriethylammonium chloride catalyst (TEBAC) are added. Then, 780 g of potassium carbonate are added to the reaction mixture.
4. The heating of the water or oil bath is set to 40°C.
5. The reaction mixture is stirred for 48 h in the warm bath.
6. A 30% sodium hydroxide (NaOH) solution in water, 450 ml, is prepared beforehand.
7. After 48 h, the stirrer is switched off. The reaction mixture (liquid layer without sediment) is decanted into a large beaker.
8. 1 liter of pure distilled water is poured into the beaker and mixed well.
9. A glycidyl ester layer is separated. The layers are separated with the aid of a separating funnel.
Note: The glycidyl ester is used in the following reactions without purification. If a chemist wants to use it as a product, he has to distill it from the secondary reaction products due to an excess of ethyl 2-chloropropionate.
Synthesis of glycidic acid (sodium salt) of BMK BMK ethylglycidate
10. The glycidyl ester is reloaded back into the clean reaction flask.
11. The previously prepared and cooled NaOH sln. is poured into the dropping funnel.
12. The stirrer is switched on. NaOH 30% ac. 450 ml of solution is slowly added to the reaction mixture. The temperature of the reaction mixture should be kept below <30°C.
13. The reaction mixture is then stirred for 12 h at room temperature.
14. After a while, 500 ml of distilled water is added and the mixture is slightly warmed (not more than 60°C).
15. 500 ml of benzene, toluene or other similar solvent is poured into the heated reaction mixture.
16. The stirrer is switched off. The layers are formed.
17. With the aid of the separating funnel the reaction by-products (not the previously distilled ester by-products) are removed. The water layer with dissolved BMK glycidic acid (sodium salt) is separated again in the flask.
Synthesis of phenylacetone (P2P) from BMK-glycidic acid (sodium salt)
18. Using the dropping funnel, concentrated aqueous hydrochloric acid (HCl) (37 %) is carefully poured into the flask until pH 1 is reached.
19. The mixture is heated to 60°C and decarboxylated with constant stirring for 5 h.
20. Then, the stirrer is turned off and the mixture is separated into two layers. The BMK layer is a top layer.
Note: If the mixture cools down, the BMK layer will remain at the bottom.
21. The BMK layer is separated in a beaker using a separating funnel for further synthesis.
Note: After a while, the remaining water in the beaker is completely separated from the BMK oil.
The yield of BMK is ~300 ml (82%).
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