US2733257A - Preparation of chlorphenoxy - Google Patents

Description

United States Patent PREPARATION OF CHLORPHENOXY ACETONITRILES Harry James Barber and Maurice Berkeley Green, Degenham, England, assignors to May & Baker Limited, Dagenham, England, a British company No Drawing. Application December 3, 1951, Serial No. 259,716

Claims priority, application Great Britain December 6, 1950 8 Claims. (Cl. 260-465) 2 pounds) are of considerable importance as plant growth regulants and selective herbicides.

Conversion of the chlorphenoxymethyl chloride in chloiphenoxyacetonitrile by mctathetical reaction with an alkali metal cyanide must, as hereinbefore mentioned, be effected in a solvent medium which consists at least predominately of a ketonic solvent with a minor proportion of water if a satisfactory yield is to be obtained. The amount of water employed should be the minimal quantity required to keep the alkali metal cyanide in solution; less water is required, and in consequence a higher yield obtained, in the case of sodium cyanide which is, therefore, the preferred cyanide. The results of some of the experiments carried out for the purpose of determining 1 the conditions necessary for obtaining a satisfactory yield This invention is for improvements in or relating to the of the nitrile in the case of the conversion of 2:4-dichlorproduction of chlorphenoxy compounds, in particular pi y y ch1c1"1dc i p c c chlol-phenoxyacetonitriles d to h production h trile are shown in the following table 1n which is set out from of chlorphenoxyacetic acids and their derivatives. the (EOI ldIHC-HS of react on and th per n y Weight Chlorphenoxyacetonitriles, especially the 2:4-dichloro 29 0f H f f It IS cvldcnt from thls table that c compound, were hitherto available only from the corcclvcnt ccndltlcfls cmplcycd In accordance Wlth the responding substituted acetic acid, or were formed by the ventlon as compared to the other reaction conditions interaction of the corresponding phenol and chloracetoni noted in the table ensure a spectacular increase in yield trile, the latter compound being prepared from chloracetic of the desired nitrile. TABLE Temp. 2:4-Dichlor- Expt. 0 'liine yanlde Solvent dephenoxyaceto- N0 grees (Hours) nitrile 1 KCN, 1.1 moles Dry methanol. 24 2 KCN,1.1 n triles.... Dry acetone... 20 24 very little. 3....-." KCN, 2.0 moles..." Dry methano 65 2 15%. 4 KCN, 2.0 moles. Glycerol 9045 2 intracfable tarry prot not. 5 KCN, 2.0 moles.-... Acetone-l-water 60 234 69%. 6 KCN, 2.0 moles Aietoifieiwater bufiered 60 2% 63%.

0 D 7 KCN, 2.0 moles. MEK +water. 60 2% 71%. 8 NaON, 1.0 mu; Acetcne+water 6O 2% 70%. 9... NaCN, 2.0 moles.-. o 60 2% 82%. 10 KCN, 2.0 moles.-. Dioxan+alittle water. 80-85 2 7%. 11 KON, 2.0 moles o 80-85 5% 24%.

I ME K=methyl ethyl ketono.

acid by the classical sequence of operations to convert the carboxy group into a cyano group i. e. via an ester and amide.

It is the object of the present invention to provide an improved, more specifically a more economic, method of preparing the said nitriles such as to render them convenient intermediates not only for the production of those derivatives of the corresponding substituted acetic acids which cannot easily be obtained from the acids themselves but also for the production of the acids and deriva tives of the type of the esters and salts.

It has been unexpectedly found that chloranisoles obtainable by the chlorination of anisole under conditions favouring nuclear chlorination can be employed as starting materials forthe production of the required nitriles and, provided that various operating conditions hereinafter referred to are observed, that the overall process offers decided commercial advantage over the hitherto known processes for producing the said nitriles.

In accordance with the present invention, a chlorphenoxymethyl monochloride is reacted with an alkali metal cyanide, preferably potassium or sodium cyanide, in a solvent medium consisting predominately of a ketonic solvent and containing a minor proportion of water.

Production of 4-chlor-, 2:4-dichlorand 2:4:6-trichlorphenoxyacetonitriles in this Way followed by alkaline hydrolysis or alcoholysis represents a particularly favourable method of manufacture of the corresponding chlorphenoxyacetic acids and esters respectively as compared with the methods hitherto employed for producing these compounds which (especially the 2:4-dichlor com- Example I Anisole (108 g.) is chlorinated at a temperature not exceeding C. until the weight has increased by 69 g. Phosphorus pentachloride (10.5 g.) is added and chlorination is continued at 190200 C. until the weight has increased by a further 34.5 g. Carbon dioxide is passed through to remove hydrogen chloride and excess chlorine, and the yellow oily product is poured into ice and water, extracted with ether and the ether extract washed twice with ice-cold N caustic soda solution, then twice with ice-water and finally dried over anhydrous magnesium sulphate. The ether is evaporated off and the residual oil is dissolved in 500 cc. acetone.

This solution is added gradually over a period of two hours to a vigorously stirred mixture of 400 cc. acetone and a solution of potassium cyanide g.) in water (300 cc.) heated to 65 C. The resulting dark brown solution is heated under reflux for one hour at 80 C. then poured into a mixture of ice-water (3000 cc.) and 2N caustic soda solution (500 cc.). An oil separates which solidifies'onstanding and is filtered off, washed with water and'pressed as dryas possible.

This solid is boiled under-reflux for two hours with 25% w./v. caustic soda solution (1000 co), the mixture is then cooled in ice and the solid isfilteredofi, washed with successive small amounts of ice-waterand pressed as dry as possible. It is then redissolved in boiling'water (4000 cc.-). An insoluble oil remains which solidifies on coolingto 80 C. and is filtered off at that temperature, washed with warm water and dried, giving bis-(2:4-dichlorphenoxy)-1nethane (42 g.) M. P. 98-l00 C. The filtrate is treated with charcoahfiltered hot and made acid to Congo red with hydrochloric acid. The precipitated solid is filtered ofi, washed with water and dried, giv-ing 2:4-dichlorphenoxyacetic acid (.132 g.), M. P. 140-142 C..in 60% yield.

Example II -A solution of 38.5 g. of sodium cyanide in 57.5 cc. of hot water is added to 192 cc. of acetone stirred at 60 C. A solution of 81.2 g. of 'crude 2:4-dichlorphenoxymethyl chloride in l92 cc. of acetone is added drop-wise during one hour, with vigorous stirring. The brown mixture is refluxed for two hours then poured into a mixture of 1.15 litres of ice-water and 192 cc. of 2N caustic soda solution. The solid is filtered off, washed with water and pressed dry.

The solid is boiled under reflux for two hours with 385 cc. of 25% w./v. caustic soda solution and the mixture cooled somewhat and the solid filtered off, washed with hot water and dried, giving 11.2 g. of bis-(2:4-dichlorphenoxy)-methane. The filtrate is acidified to Congo red and the solid filtered off, washed with water and dried, giving 72 g. of 2:4-dichlorphenoxy acetic acid, M. P. 140- 142 C.

Example Ill 4-chlorphenoxymethyl chloride, M. P. 105-115 C., 15 mm., M. P. 29-30 C. is converted into the corresponding nitrile and thence into the corresponding acid in analogous manner to that described in Example II.

We claim:

1. A process for the preparation of a chlorphenoxyacetonitrile which comprises reacting a chlorphenoxymethyl mono-chloride with an alkali metal cyanide in a solvent medium consisting of a ketonic solvent and a minor proportion of water.

2. A process according to claim 1 in which the ketonic solvent is acetone.

3. A process according to claim 1 in which the ketonic solvent is methyl ethyl ketone.

4. A process forproducing 2:4-dichlorphenoxyacetonitrile which comprises reacting 2:4-dichlorphenoxymethyl chloride with an'alkali metal cyanide in a solvent medium consisting of a ketonic solvent and a minor proportion of Water.

5. A process for the preparation of-a chlorphenoxyacetonitrile which comprises reacting a chlorphenoxymethyl mono-chloride with sodium cyanide in a solvent medium consisting of a ketonic solvent and a minor proportion of water.

6. A process according to claim 5 in which the ketonic solvent isv actone.

7. A process according to claim 5 in which the ketonic solvent is methyl ethyl ketone.

8. A process for producing 2:4-dichlorphenoxyacetonitrile which comprises reacting 2:4-dichlorphenoxymethyl chloride with sodium cyanide in a solvent medium consisting of a ketonic solvent and a minor proportion of water.

References Cited in the file of this patent Marvel et al.: J. Am. Chem. Soc., vol. 44 pgs. 2645-7 (1922).

Plazek: Chem. Abstracts, vol. 25, pgs. 1504-5 (1931).

Weygand et al.: Chem. Abstracts, vol. 35, col. 1773-4 (1941).

Asolkar et al.: Chem. Abstracts, vol. 40, col. 5406 (1946).

Salmi et al., Chem. Abstracts, vol. 40, pgs. 6491-2 (1946).

Claims (1)

1. A PROCESS FOR THE PREPARATION OF A CHLORPHENOXYACETONITRILE WHICH COMPRISES REACTING A CHLORPHENOXYMETHYL MONO-CHLORIDE WITH AN ALKALI METAL CYANIDE IN A SOLVENT MEDIUM CONSISTING OF A KETONIC SOLVENT AND A MINOR PROPORTION OF WATER.