Reaktion #55088

Reaktionsgleichung

HCl

sodium chloroacetate

thiourea

NaOH

p-fluorobenzylchloride

→

said acid

Ausbeute 90.6%

p-Fluorobenzylthioacetic acid

Ausbeute 90.6%

Lösungsmittel

methylene chloride

water

cyclohexane

water

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigeequipped with a magnetic stirrer, a condenser
2. 2
   TemperaturThe mixture is heated
3. 3
   Temperaturto reflux
4. 4
   Temperaturboiling is maintained for about 15 minutes
5. 5
   TemperaturThereafter the mixture is cooled
6. 6
   TemperaturThe whole is heated
7. 7
   Temperaturunder reflux for about 30 minutes
8. 8
   Temperaturcooled
9. 9
   TemperaturThereafter the whole is heated
10. 10
    Temperaturunder reflux for 30 minutes
11. 11
    Temperaturcooled
12. 12
    Sonstigethe oil obtained
13. 13
    Waschenthe solution is washed with a dilute solution of sodium bicarbonate
14. 14
    Filtrationfiltered over charcoal
15. 15
    Sonstigethus precipitates
16. 16
    Filtrationis filtered off

Vorschrift

A solution of 15.2 g (0.2 mol) of thiourea in 100 ml of water is introduced into a 1 liter 3-necked flask equipped with a magnetic stirrer, a condenser and dropping funnel, and 28.9 g (0.2 mol) of p-fluorobenzylchloride are introduced, at 50°-60° C., in a single operation. The mixture is heated to reflux and boiling is maintained for about 15 minutes; the solution becomes limpid. Thereafter the mixture is cooled and a solution of 32 g (0.8 mol) of NaOH in water is added dropwise at about 60° C. The whole is heated under reflux for about 30 minutes and cooled and a solution of about 0.28 mol of sodium chloroacetate (obtained by neutralising 26.46 g of chloroacetic acid in 200 ml of water with 23.52 g of sodium bicarbonate) is added dropwise at 60°-70° C. Thereafter the whole is heated under reflux for 30 minutes, and then cooled. The mixture is acidified with 3 N HCl, the oil obtained is taken up in methylene chloride, the solution is washed with a dilute solution of sodium bicarbonate, filtered over charcoal and acidified once more with 3 N HCl and p-fluorobenzylthioacetic acid thus precipitates and is filtered off. After recrystallisation from cyclohexane, 33.4 g (yield: 83%) of the said acid are collected. Instantaneous melting point: 68°-69° C.

Quelle