Reaktion #56457

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 3N 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-flourobenzylthioacetic 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