DE1417413A1 - Herbicides - Google Patents

Description

141/4 I O

w 18622/59

Hoyden Newport Chemical Corporation New York, N.Y. (V.St.A.)

Herbicides.

The invention relates to new herbicides and to methods of inhibiting or Preventing vegetation.

It has been found that 2,3-dichloro-6-methylbenzoic acid and 2-methyl-3,6-dlchlorobenzoic acid are effective herbicides that have herbicidal activity against solitary lobed (grass-like) plants and zwelsamenlappige (broad-leaved) plants both before Show rising as well as after rising. While these two compounds are preferred, it should be noted that homologues of these two compounds are herbicides as well, and these homologues are those, at which an ethyl, propyl or butyl group replaces the methyl group in each of these compounds.

These herbicides can be used in the form of the acid or in the form of a derivative of the acid. To the Derivatives of any of these acids that may be used include their salts including their alkali salts, such as the sodium or potassium saltj of their ammonium

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umsalzes, their alkaline earth salts, such as calcium and Barium salts; and their salts of amines, such as the primary, secondary and tertiary alkylamines and the mono-, di- and trialkanolamines including ethanolamine, Dir ethanolamine and triethanolamine. The herbicide can spread also in the form of esters of this acid with aliphatic monohydric alcohols, e.g. the alkyl alcohols, methanol, Ethanol, propanol, butanol, and the monohydric ether alcohols such as ethylene glycol monoethyl ether, diethylene glycol monoethyl ether and triethylene glycol monobutyl ether, are present. Amides of the acid can also be used.

These compounds, either in the form of the acid or the above-mentioned derivatives, can be applied to existing plants, to the soil or other medium normally bearing plant growth, or to both. The herbicide can be applied to an area containing a crop to inhibit the growth of weeds in the area, or it can be applied to an area to keep it free from all plant growth. The herbicide according to the invention is more effective against double-lobed plants than against single-lobed plants, and it can be applied to a stand of single-lobed plants such as maize or wheat to inhibit the growth of double-lobed weeds in the crop area by preventing the growth of existing weeds are inhibited and / or 909836 / U76

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the future growth of weeds from seeds in the area is inhibited. When the herbicide is on a corn or wheat field is applied at the time of sowing or after the seedlings have emerged, then prevents 2,> - Diehlor-6-methyl-benzoic acid the growth of broad-leaved weeds without damaging the crop.

Although the herbicidal compound can be used as such, it is generally used together with a Carrier used. You can use the area in which plant growth is to be controlled in the form of a Solution or emulsion or in the form of a solid, finely divided carrier which is mixed with the herbicide or on which the herbicide has been deposited.

The concentration of dichloromonoalkybenzoic acid in the pffence killer can be used to a large extent vary and depends on a number of factors, the most important of which is the amount of per unit to be treated Area to be applied agent and the type of

That
plants to be treated. It can also contain other herbicides.

2,3-dichloro-6-methylbenzoic acid and 2-methyl-3,6-dichlorobenzoic acid can be made by any suitable process. The process which is used for the manufacture is preferred by 2,3-dichloro-6-methylbenzoic acid,

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U17413

comprises the nuclear dichlorination of o-xylene and the separation of the dichloro-o-xylene from the mono-o-xylene and trichloro ^ -oxylene formed by fractional distillation. It should be noted that the calibration chloro-xylene fraction is a mixture of isomeric compounds and that their subsequent reactions lead to products that are also mixtures of isomers. The dichloro-oxylene is reacted with a sufficient amount of chlorine at an elevated temperature to convert one of its methyl groups into a chloromethyl group. That I The resulting methyl dichlorobenzyl chloride is then treated with an alkali salt of a saturated monocarboxylic acid, e.g. Sodium formate, potassium acetate or sodium butyrate, reacted to form a methyl dichlorobenzyl ester, the is then oxidized to methyldichlorobenzoic acid. The "pro-

product is a mixture of isomers including 2,3-dichloro-6-methy! benzoic acid. This isomer can be derived from the Mixture are separated for example by a procedure which comprises a selective esterification, or the mixture of isomers of the 2,3-diochloro-6-methyl isomer can be used as such in plant destroying agents.

While o-xylene is the preferred source material in this process for making 2,3-di-methyl-6-methylbenzoic acid, any mixture of xylenes containing a significant amount of o-xylene can be used. For example, technical grade xylene, which is a

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Mixture of o-xylene, m-xylene, p-xylene and ethylbenzene is used in the method according to the invention. When using a mixture of xylenes the herbicidally active isomer can be separated from the other products, or it can be the resulting one Mixture of products to be used in herbicides. In the latter case, however, is the herbicidal activity of the product depending on the o-xylene content of the Xylene deletion with products obtained from Xy! Oil mixtures which contain a small amount of relatively inactive o-xylene, and those made from xylene mix " genes are obtained which contain larger amounts of o-xylene and approach the activity of products made from pure o-xylene.

That from o-xylene according to the procedure described here The product produced is a mixture of isomeric methyldiochlorobenzoic acids including 2,3-dichloro-6-me thy! benzoic acid, 2-methyl-j5,4-dichlorobenzoic acid and 2-methyl-4,5-dichlorobenzoic acid. It has been found that, if a given amount of this Iaomeregemisohes in one Vegetables are used, the obtained Results are roughly equivalent to those obtained with an agent containing the same amount of pure 2, ^ - Diohlor-o-Methy! Benzoic acid contains. the other isomers than 2, jJ-dichloro-6-methy! benzoic acid show herbicidal activity neither alone nor in combination, with the exception of 2-methyl-15,6-diochlorobenzoic acid, and whether

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even a small amount of this last-mentioned isomer is present, the amount is not sufficient for taking into account the unexpected effectiveness of the mixture of isomers get. The inner mixture therefore provides a synergistic one Effect by showing herbicidal activity greater than the sum of the activities of the individual Isomers in the amounts present in the mixture. The relative amount of 2,3-dichloro-6-methylbenzoic acid, that in the mixture of isomers of dichloromethylbenzoic acid present can vary widely; However, if the percentage of this particular isomer is very low it is generally preferable to use somewhat larger amounts of the mixture.

Example 1.

This example includes the preparation of a mixture of isomeric methyldiochlorobenzoic acids des 2, J-Dlchlor-o-methyl isomers described.

Chlorine gas was bubbled through a mixture of 500 g of o-xylene and 5 g of iron filings at -15 ° to -10 ° C. for 5 hours. By the end of that time, the weight of the mixture had increased by $ 2J> g. The chlorinated o-xylene mixture was washed with five 1000 ml aliquots of water and then distilled under reduced pressure. The dichloro-o-xylene fraction, which boiled at 104 to 108 ° C. / 12-14 mm, weighed 331.3 g and contained 40.1 % Cl (calculated for dichloroxylene, 40.6 % Cl).

200 g of dichloro-o-xylene were at for 3 hours

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205 to 210 ° C chlorinated. At the end of that time it had the weight of the reaction mixture increased by 39s, accordingly the calculated weight increase for the addition of 1 gram atom of chlorine per gram of molecular weight of the dichloro-o-xylene. This results from the side chain chlorination described above resulting methyldichlorobenzyl biloride was used with 18, 15 g sodium formate and 600 ml acetic acid for 8 hours heated at reflux temperature. After removing the acetic acid by distillation under reduced pressure and washing of the product with 500 ml of water became 215.4 g of crude Obtained methyl dichlorobenzyl formate. An oxidation to the corresponding acid was brought about that 105 g of the ester with 61.7> 5 g of 70% nitric acid during 3 hours were heated at reflux temperature. That Oxidation product was cooled, poured into 1000 ml of water

three
poured and then extracted with * 300 ml portions of benzene.

The combined benzene extracts were extracted with 410 g of a 5 # strength sodium hydroxide solution. After the addition of 15 ml of 36% hydrochloric acid, the sodium hydroxide extract was treated with 3 g of activated charcoal and filtered. The filtrate was acidified with 100 g of 36% hydrochloric acid, and the precipitated product was isolated by filtration and dried at 55 to 60.degree. Approximately 5.8 g of a product were obtained which was mainly composed of a mixture of 2,3-diehlor-6-methylbenzoic acid, 2-methyl-3,4-dichlorobenzoic acid and 2-methyl-4,5-dichlorobenzoic acid with a small amount present Amount of 2-methyl-3,6-dichloro

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benzoic acid.

Example 2.

75 g of an isomer mixture prepared according to the procedure described in Example 1 were heated for 8 hours at reflux temperature with 750 ml of methanol and 20 ml of concentrated sulfuric acid. After the unreacted methanol was removed by distillation under reduced pressure, the residue was dissolved in benzene. This solution was washed with three 100 ml aliquots of water and then extracted with 320 g of 5% sodium hydroxide solution. The subsequent treatment of the benzene solution is described in Example 3. The alkaline extract was treated with activated charcoal at 50 ° C., filtered, cooled to 20 ° C. and acidified with 56% hydrochloric acid. The precipitated acid was isolated by filtration and then dissolved in 150 ml of dry ether. The ether solution was dried over sodium salad and then evaporated to dryness to give 21.6 g of crude 2,3-dichloro-6-methylbenzoic acid. The crude product was recrystallized twice from cyclohexane, twice from ligroin and then from nlfcromethane. The pure 2,3-dichloro-6-methylbenzoic acid resulting from this procedure had a melting point of 91 to 92 ° C. and an acid number of 274 (calculated for CgH ₆ O ₂ Cl ₂ , acid number 274).

Example 3.

The benzene solution of the methyl esters of methyldichlorobenzoic acid, from which 2,3-dichloro-6-methylbenxoic acid

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had been extracted (see Example 2), it was evaporated to dryness. The obtained crude methyl esters were heated with 11.8% of nafcrium hydroxide, 23.6 g of water and 200 ml of ethanol for 8 hours at reflux temperature. After removing the ethanol and water by distillation under reduced pressure, the residue was dissolved in 100 ml of water and the resulting solution was clarified by filtration, acidified to pH 1 and filtered again. After drying at 55-60 ° C, the crude product weighed 28.5 %. This material, which consisted of a mixture of 2-methyl-3,4-dichlorobenzoic acid and 2-methyl-4,5-dichlorobenzoic acid, was recrystallized purified from benzene.

Example 4.

A series of experiments was carried out in which groups of soil-containing bowls with canola, Gansefus8, alfalfa, Wioken or timothy grass seeds sown became. Each tray contained one type of seed and was treated with only one herbicide at one dose. The herbicide was in the form of an aqueous solution of the sodium salt of pure 2,3 * Dlohlor-6-methy! benzoic acid applied. The solution used was that of the sodium salt was applied in an amount that corresponds to that in the following table I in the column! {Dosage " specified amount of 2,3-dichloro-6-methylbenzoic acid was equivalent. For comparison purposes, sohales have been added to each

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Group treated with aqueous solutions containing the sodium salt of "2,4-D" (2,4-dichlorophenoxyacetic acid). In each case the herbicide was applied to the soil in the trays on the same day that the seeds were brought in. The results of the experiments were observed 10 days after sowing.

In Tables I, II and III below, the letters ¹¹ D "," S ^H and "i" relate to the density of the plants, the size of the plants and the damage to the plants. The effectiveness of the herbicides, which was determined by comparison with untreated seeds, is indicated by the numbers 0 to 5 in increasing order of effectiveness. The value 0 means no herbicidal activity and the value 5 means maximum herbicidal activity.

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Tabel I. S. 3 I. D. 4-D " I. 1 2 plants dosage 3 4th 2 0 1 3 art kg / ha 5 2 1 S. 1 3 2 3 3 1 1 0 Rapeseed 0.285 2,3-dichloro-6-methyl- "2, 3 ui 4th 3 4th 1 0.570 benzoic acid 3 1 0 3 1 1 i, l4o D. 3 2 0 4th 1 3 2.280 1 2 Previous year 0 0 1 Goosefoot 0.285 2 4th 3 2 0 2 0.570 4th 1 0 2 1 i, i4o 4th 4th 3 1 2 2 2.280 0 2 4th 2 1 4th alfalfa 0.285 1 3 4th 3 3 4th 0.570 1 3 3 0 4th l, i4o 3 3 3 1 4th 2.280 0 3 4th 2 0 Vetch 0.285 - 1 3 4th 3 1 0.570 j5 3 2 0 2 1,140 3 4th 2 1 3 2.280 1 3 2 1 Timothy grass 0.285 2 4th 3 2 0.570 3 2 l, i4o 4th 3 2.280 1 2 2 4th

From Table I it can be seen that 2,3-Diohlor-6-methyl-benzoic acid as a herbicide somewhat more effective than ^M 2,4-D ^w is, if, before the rising of both zweisamenlapplgen plants (rape, goosefoot, alfalfa and vetch) as well as solitary lobed plants (timothy grass) is used.

Example 5,

Groups of bowls containing soil were mixed with rape, Goosefoot, millet and / or “oak grass seeds sown. Every bowl

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contains seeds of only one species and was made with only one Herbicide treated at one dosage. The herbicides came in the form of a water-based solution of their sodium eels applied, wherein the amount of solution used was such that the amount of salt was applied that with was equivalent to the amount of acid indicated in Table II in the "Dosage" column. The herbicidal solutions were made applied to the soil in the bowls on the day the seeds were brought in. Di · results were sown on the specified number of days after sowing observed.

Table II

Plant species

dosage

kg / ha

Mixture of isomeric methyldichlorobenzoic acids derived from o-xylene

2,> dichloro-6-methylbenzoic acid

r Ta «· P. 4th I. Days p β I. Rapeseed 1.14 19th 3 4th 4th 24 3 4th 3 2.28 19th 3 3 k 24 5 4th 4th Goosefoot 1.14 19th I. 3 2 27 1 2 1 2.28 19th 2 2 3 27 2 2 1 Timothy grass 1.14 7th 4th 4th 2 24 4th 4th 4th 2.28 7th 0 2 3 24 5 - - millet 1.14 19th 0 2 1 24 2 4th 1 2.28 19th 1 24 1 4th 1

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Plant dosage 2-Methyl-4,5- Qemisoh of 2-Methylart kg / ha diohlorbenzoe- 3 * 4-dichlor- and 2-

acid ethyl-4,5-dichlorobenzoic acid

1 * 1 * Days D. S. I. Days D. S. I. Rapeseed 2.28 1.14 4th O 1 O 12th O 1 O Qänsefuss 2.28 _ 1.14 4th O 1 O 12th 1 1 1 Timothy grass 2.28 12th O O O 1.14 12th O O O millet 2.28 _ mm mm 4th O O O - - -

The values in Table II show that the herbicide Activity of the mixture of acids derived from o-xylene, which 2,> - Diohlor-6-methylbenzoic acid, 2-methyl-3,4-dichlorobenzoic acid and 2-methyl-4,5-dichlorobenzoic acid contains, which is obviously equivalent to pure 2,3-dichloro-6-methyl isomers. Since the 2-methyl-4,5-dichloro isomer and the Gemisoh these isomers with the 2-methyl-3,4-dichloro isomer have a low herbicidal activity, the Oemlsoh the isomeric acids a-Bchliesslioh 2, ^ - Diohlor-o-methylbenzoic acid has a synergistic herbicidal effect by increasing its activity is as the sum of the activities of the individual acids based on the amounts of each present in the oeraisoh Acid.

Example 6. Soups of bowls, dl «« it rape- »Oänsewfues-, resp.

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Timothy-grass seeds were sown with watery fro bidden loun ten sprayed 14 days after sowing. the The amount of solution used was in each case such that 3 the amount of salt applied was the same as the amount of acid specified in Table III in the "Dosage" column was equivalent. In each case, the results were observed days after application of the herbicidal solution.

Table III.

Plant dosage mixture derived from xylene from oart kg / ha

isomeric methyldichlorobenzoic acids

• 2.4-11 "

1.14 D. S. I. D. S. I. Rapeseed 2.28 0 2 2 0 2 I. 0.57 0 2 2 1 3 2 Osseous foot 1.14 2 2 2 2 2 3 2.28 3 3 3 3 3 3 0.57 3 4th 4th 3 4th 0 millet 1.14 0 1 0 0 2 1 0 1 0 0 2

While 2,3-diochloro-6-methylbenzoic acid and 2-methyl-3,6-diohlobenzoic acid have been considered in more detail Homologues of these two acids are also effective herbicides for the same purposes. All of these compounds are represented by the formula

JOOH
R.

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B / \ D

In this formula, R or R denotes an alkyl radical having 1 to 4 carbon atoms, ie the alkyl radical can be methyl, ethyl, propyl or butyl. R and R i comprise one and only one alkyl radical, and either R or R ₁ represents a chlorine atom. These 2,3-dichloro-6-alkylbenzoic acids and 2-alkyl-3,6-dichlorobenzoic acids can be prepared in any convenient manner.

For example, 2-propyl-15,6-dichlorobenzoic acid be prepared from o-bromotoluene. If this material is nucleus dichlorinated, one of the isomers formed is 2-bromo-3,6-dichlorotoluene. The methyl group can through Oxidation with nitrogen oxide and air into a carboxyl group being transformed. By the Fittig reaction, in which propyl bromide in the presence of sodium metal is used, the bromine of 2-bromo - ^, 6-dichlorobenzoic acid is replaced by a propyl group to make 2-propyl-3,6-dichlorobenzoic acid to build. When using methyl, ethyl or butyl bromide instead of propyl bromide can use the corresponding methyl, ethyl or butyl compounds be generated.

Propylbenzene can be monobrominated to form a mixture of o- and p-bromopropylbenzene. These isomers can be separated by distillation. Nuclear dichlorination of the o-bromine compound produces a mixture of 2-γοπι-; 5 * 4- <11ο1ι1ογ- and 2-bromo-j5,6-dichloropropybenzene. Through the Grignard reaction, in which magnesium is used and on which treatment with

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COp gas in the presence of water follows, the bromine atoms replaced by carboxyl groups. The resulting reaction mixture contains 2-propyl-15,6-dichlorobenzoic acid and 2,3-DiChIOr-O-PrOPyIbCnZOeSaUrC. These acids can if desired separately or as such as Herbicide can be used. If toluene, ethylbenzene or butylbenzene is used as the starting point, the corresponding Dichloromonoalkylbenzoic acids are formed.

8Oδ £ 36/147 8

Claims (10)

H17413 claims. 1.) Plant killers, characterized by the content of a carrier uad a herbioid active Amount of a herbioid consisting of monoalkyldichlorobenzoic acid and the salts or amides of this acid, which the formula COOH Cl in which one of the constituents R and R _{1 is} chlorine and the other v; in the alkyl radical rait I denotes up to 4 carbon atoms. ' 2.) Plant killing agent according to claim 1, characterized in that the herbioid consists of 2,3-diohlor-6-methy! Benzoic acid or a salt of this acid. j5.) Plant killing agent naoh claim 1, characterized in that the herbioid from a mixture of methyldiochlorobenzoic acid isomers exists 2,3-chloro-6-methylbenaoic acid or its sodium salts contains. 4.) Plant fertilizers naoh Claim 1, characterized by the fact that the herbioid is a mixture of methyl-diohlorbenatoevKuren consists, dlt aioh from , the conversion of a methyl group of diohloroxylene into a carboxyl group « 909836 / U76 BATH 5.) plant killing agent according to claim 1, characterized characterized in that the herbicide is made up of a mixture of methyldichloroboitzoic acid isomers including 2,3-dichloro-6-methylbenzoic acid, 2-methyl-3,4-dichlorobenzoic acid, 2-methyl-4,5-dichlorobenzoic acid and 2-methyl-3,6-dlchlorobenzoic acid consists. 6,) Process for the preparation of a mixture of methyldichlorobenzoic acids including 2, j5-dichloro-6-methylbenzoic acid, characterized in that o-xylene is chlorinated to form a mixture of isomeric dichloro-o-xylenes, the dichloro-o- heated xylenes with chlorine and about 1 gram-atom of chlorine per gram molecule dichloro-o-xylene to form a mixture of MethyldlchlorbenzylchlorId isomers reacted to form these Methyldichlorbenzylchlorld isomers with an alkali salt of a saturated Monooarbonsäureverestert to give a mixture of isomeric Methyldichlorbenzylestern this 3äure, and Ester oxidized to form a mixture of isomeric methyldichlorobenzoic acids. 7.) Process for the preparation of 2,3-diehlor-6-methy! Benzoic acid, characterized in that o-xylene is chlorinated to form a mixture of isomers of dichloro-o-xylenes, the dichloro-o-xylene isomers of the separates other chlorination products by fractional distillation under reduced pressure, heated the Diohlor-o-eylene isomer fraction with chlorine in the amount of about 1 gram atom of chlorine per gram molecule of dichloro-o-xylene , vem such a 909836 / U76 BATH Mixture of isomeric methyldichlorobenzyl chlorides too form, these isomeric methyl dichlorobenzyl chlorides with an alkali salt of a saturated monocarboxylic acid with 1 to 5 carbon atoms esterified to give a mixture of isomeric Methy_ldiehlorbenzylestern this acid form the esters to the corresponding isomeric methyldichlorobenzoic acids oxidized and 2,3-dichloro-6-methylbenzoic acid from the mixture of isomeric methyldichlorobenzoic acids separates. 8.) Process according to claim 6 or J, characterized in that the alkali salt used in the esterification stage is sodium formate. 9 ·) Plant killers, characterized by the content of a mixture of methyldlchlorobenzoic acids resulting from the conversion of a methyl group of dichloroxylene are obtained into a carboxyl group. 10.) Plant killers, characterized by the content of a mixture of MethyldiehlorbenzoesMure isomers including 2,> - dichloro-6-ethylbenzoic acid, 2-methyl, 3,4-dichlorobenzoic acid, 2-methyl-4,5-dichlorobenzoic acid and ^ -ß 909836 / U78 BATH