SU119185A1 - Method for preparing 2,4-dichlorophenoxyacetic acid gamma chlorochrotyl ester - Google Patents

Description

Sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-DU) is widely used to control weeds in agriculture. Various derivatives of the indicated acid were also synthesized and studied, of which the most active herbicides were its esters, in particular butyl ether. However, the widespread use of the latter is hampered by its significant volatility, etc.

A method is proposed for preparing a 2,4-dichlorophenoxyacetic acid ester not previously described in literature, namely, j-chlorocrotyl ether, suitable as a herbicide for controlling weeds of cereals and the deficient butyl ester of said acid. A distinctive feature of this method is that y-chloro-hydroxy ester is obtained by reacting 2,4-dichloro-phyoxy-acetic acid sodium salt with 1,3-dichlorobutene-2 in the presence of pyridine or the free acid with -chloro-alcohol,

O-CH-C; 4- Н, С.-С С-СНз -С1- / -0-СН, -С

/ O 9 C1 0№

OCH, - С С-СНз + NaCi Н С1

C1H C1

The 2,4-dichlorophenoxy-acetic acid chloro-chloroyl ester is a crystalline substance with mp. 33-34 ° and so on. Kip. 30–35 ° above mt. the corresponding butyl ether; it dissolves in benzene, chloroform, ether, salt and transformer oils, it is difficult to dissolve in alcohol and it does not dissolve in water. Field trials of the ester prepared by the proposed method showed that it is a highly active herbicide.

Example 1. In a 0.5 l round-bottom flask equipped with a mechanical baffle with a mercury shutter and reflux condenser, 145.8 g (0.6 mol) of 2,4-dichlorophenoxyacetic acid sodium salt, 180 ml of 1,3-dichlorobutene, are placed. 2 with t. Kip. 120-127 ° and 0.5 g of pyridine. The mixture is heated with stirring in an oil bath at 130-135 ° for 4-4.5 hours. At the end of the reaction, the reaction mass is filtered off, the excess dichloride is removed by iodine by a weak vacuum (water jet pump), and the residue is distilled in vacuum, collecting the fraction boiling at 186-188 ° (1 g). The yield is 145.2-148.6 g or 78.1-80% of the theoretical; m.p. the resulting ester 32-33 °.

Note. After removing the excess dichloride, the reaction product can be isolated without vacuum distillation. For this purpose, the residue is triturated with cold water, then (to remove traces of acid) it is treated with 2% sodium hydroxide solution or soda. The resulting crystalline mass is filtered from the liquid phase and washed several times with cold water. Air-dried crude ether has an mp. 31-32 ° and is obtained with almost the same yields as with vacuum distillation.

Example 2. In a 0.25 l Würz flask equipped with a thermometer and a descending cooler, 154.7 g (0.7 mol) of 2,4-dichlorophenoxyacetic acid with a melting point are placed. 138-139 ° and 97 g (0.91 mol) of 7 chlorocrotic alcohol with m.p. 150-162 °.

The flask is immersed in an oil bath equipped with a thermometer and slowly heated, bringing the bath temperature to 170 °, after which the heating is stopped. After a few minutes, a boor reaction begins, followed by distilling off the water with a slight admixture of alcohol. Further distillation of the water is carried out at 150-155 ° (oil bath temperature). As soon as the distillation of the main amount of water ends, the temperature inside the flask gradually drops to 85 °. When this stop heating. In total, about 10-II ml of water and 6-7 ml of alcohol are distilled. The residue is taken up in a Claisen flask and distilled in vacuo to collect a fraction boiling at 186-188 ° (1 mm). The yield is 174.5-182 3 or 80-84% of the theoretical; m.p. the resulting ester 33-34 °.

After removal of excess alcohol, the reaction product can be isolated without vacuum distillation, as indicated in the note for Example 1.

C + HOCH-C-C-CH3

oni C1

-c s-sns + nr