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 hydrolysed to P2P. This reaction is not water sensitive like the synthesis of BMK methyl glycidate. There are advantages such as a rather 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 reaction flask of 3 L, equipped with reflux condenser, top stirrer and 250 mL balanced pressure dropping funnel.
- Funnel
- Retort holder and clamp for securing the apparatus
- pH indicator paper
- Water/oil bath
- Retort holder and clamp for securing the apparatus
- Laboratory 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
BMK ethyl glycidate synthesis from benzaldehyde.
1. 900 ml of dimethylformamide is poured into a 3-litre four-neck round-bottomed reaction flask equipped with a reflux condenser, an overhead stirrer and a dropping funnel.
2. Then 300 ml of benzaldehyde is added. An overhead stirrer is switched on.
3. 540 g of ethyl 2-chloropropionate is poured into the reactor. Thirty-two g of benzyltriethylammonium chloride catalyst (TEBAC) is added. Then 780 g of potassium carbonate are added to the reaction mixture.
4. The heating of the water or oil bath is set at 40°C.
5. The reaction mixture is stirred for 48 h in the warm bath.
6. A 30 % sodium hydroxide (NaOH) solution in water is prepared in advance, 450 ml.
7. After 48 h, the stirrer is switched off. The reaction mixture (liquid layer without sediment) is decanted into a large beaker.
8. Pour 1 litre of pure distilled water into the beaker and mix thoroughly.
9. Separate a glycidyl ester layer. 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 distil it from the secondary reaction products because of an excess of ethyl 2-chloropropionate.
Synthesis of glycidic acid (sodium salt) of BMK BMK ethylglycidate
10. The glycidyl ester is reloaded 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 must be kept below <30°C.
13. The reaction mixture is then stirred for 12 h at room temperature.
14. After a while, 500 ml 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. Switch off the stirrer. The layers are formed.
17. Using 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. The shaker is then switched 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 some time, 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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