IL28850A - Herbicidal compositions containing n-alkoxy phenoxyalkanamide derivatives - Google Patents

Description

HERBICIDAL COMPOSITIONS CONTAINING N-ALKOXY PHENOXYALKAN AMIDE DERIVATIVES B9 ¾aiS3iS ^S'»0S?l«3S 28850/2 This invention concerns new herbicidal compositions which are effective in the control of a broad spectrum of weeds.

Many organic and inorganic substances have previously been proposed and used in attempts to control weeds. While some of these substances are partially successful, the problem of controlling the vast number of species of undesirable plant life still exists. The previously proposed substances are effective n the control of certain weeds, but no compound or composition has been discovered which caii effectively control all the species of weed without being excessively toxic and indiscriminately destroying both desirable and undesirable plant life.

In particular, herbicidally active compounds of the following Group I have been found to be useful against certain weed species, but a © relatively ineffective against others.

Group I - Compounds of the formula: 28850/2 wherein Xt, X , X_, X and X are independently 1 Δ ^ 0 selected from the group consisting of halogen, lower alkyl, lower alkoxy, and hydrogen provided a maximum of two of X., X„, X¾, X . and X are hydrogen; and Y is selected from the group consisting of ~^^2^nCOOH and -COOH wherein n is an integer from one to three; and the salts, amides and esters thereof.

The compounds of Group I, have been found to be generally effective in the control of certain weeds such as dock, mustard, pigweed, velvet leaf, spike rush and the like but generally fail to destroy other/ weeds. Various of these herbicides have been tried in an attempt to control the entire wide spectrum of wedds at rates which are non-injurious to crops, but the attempts have failed and the weeds continue to thrive, causing substantial economic losses through competition with crops, harvesting problems, low yield, and the 28850/2 like.

The object of the present invention is to provide herbicidal compositions for the control of a broad spectrum of weeds and which are capable of being applied to crops at rates compatible to the crops.

More particularly, the present invention provides a herbicidal composition which comprises a first compound selected from compounds of the formula wherein A and D are independently selected from the group consisting of hydrogen, chlorine and lower alkyl groups, provided that a maximum of one of A and D is hydrogen, A is chlorine only when D is chlorine, R' is selected from the group consisting of hydrogen and alkyl groups; R is an alkyl group; and Z is an unsubstituted alkylene group containing from one to four carbon atoms; and the alkali metal salts of the said compounds wherein R' is hydrogen; and at least one second compound selected from the compounds of Group I defined hereinabove.

Though generally, the herbicidal compositions of the present invention include combinations of two compounds, it is within the scope of this Invention to Include more than two compounds and/or an inert carrier in the compositions.

This invention also provides a method of destroying undesirable plants which comprises contacting said plants with a herbicldal composition as defined above, in a quantity which is injurious to said plants.

Unexpectedly, it has been found that the use of combinations of a first compound selected from Group (A) with one or more compounds selected from Group^ I to VII, provide herbi-cidal compositions which are effective in the control of a broad spectrum of weeds and which give results which often are unattainable at comparable rates with separate compositions of the individual herbicides.

For example, these combinations often set more rapid-ly in the control of weeds in crop areas and yet have residual herbicldal effectiveness over a longer period of time than the individual herbicldal components at equivalent rates. Also, crops are unexpectedly tolerant to these combinations.

The following exemplified compounds of Group Α· which are suitable for use as a component in the compositions of the present invention: N-Methoxy 2-methyl-4-chlorophenoxyacetamide N-Methoxy- -methyl 2-methyl-4-chlorophenoxyacetamide N-Methoxy 2,4-dichlorophenoxyacetamide N-Methoxy-N-methyl 2,4-dichlorophenoxyacetamide N-Methoxy 2,4,5-trlchlorophenoxyacetamide N-Methoxy-N-methyl 2>4 5-trichlorophenoxyacetamide N-Methoxy 4-chlorophenoxyace amide N-Methoxy 4-bromophenoxyacetamide N-Methoxy-N-methyl 4-chlorophenoxyacetamide a- (N-Methoxy-N-methyl 2-methyl 4-chlorophenoxy) , proplonamide N-Ethoxy 2-methyl-4-chlorophenoxyacetamide N-Ethoxy-N-methyl 2-methyl- -chlorophenoxyacetamide N-Ethoxy-2, 4-dichlorophenoxyacetamlde N-Ethoxy-N-methyl 2,4-dichlorophenoxyacetamide N-Ethoxy 2,4,5-trichlorophenoxyacetamide N-Ethoxy-N-methyl 2, 4, 5-trlchlorophenoxyacetamlde N-Ethoxy-N-methyl 4-chlorophenoxyacetamide N- ethoxy 2-methylphenoxyacetamide N-Methoxy-N-methyl 2-methylphenoxyacetamlde N-Methoxy-4-methylphenoxyacetamide N-Methoxy-N-methyl 4-methylphenoxyacetamide N-Methoxy 2,4-dimetbylphenoxyacetamide N-Methoxy-N-methyl 2, 4-dlmethylphenoxyacetamide N-Methoxy-N-methyl 2-ethylphenoxyacetamide N-Methoxy-N-methyl 2-lsopropylphenoxyacetamlde N-Isopropoxy 2-methylphenoxyacetamide and N-Methoxy-N-methyl 2-allylphenoxyacetamide .

The alkali metal salts of the compounds of Group (A) wherein R 1 in the formula (A) is hydrogen, are particularly useful in ,the compositions of the present invention since they are relatively soluble in water.

Exemplary of the suitable alkali metal salts are: the potassium salt of N-methoxy-2-methyl-4-chlorophenoxyacet-amlde, the sodium salt of N-ethoxy-2-methyl-4-chlorophenoxy-acetamide, the potassium salt of N-methoxy-2,4-dichlorophenoxy-acetamlde, the potassium salt of N-methoxy-4-chlorophenoxyacet-amide, the sodium salt of N-ethoxy-2,4-dichlorophenoxyacetamide, the potassium salt of N-methoxy-2,4-dimethyl-phenoxyacetamlde, Exemplary of the herbicides of Group I which are suitable for use in combination with the compounds of Group A to form the compositions of the present invention are: 2,3,6-trlchlorobenzoic acid, 2,3, ,6-tetrachlorobenzoic acid, 2-methoxy-3, 6-dichlorobenzolc acid, 2-methoxy-3,5,6-trlchloro-benzolc acid, 3 -amino-2, 5-dlchlorobenzoic acid, 3-nltro-2,5-dichlorobenzolc acid, 2-methoxy-3-nitro-5-chlorobenzoic acid, 2, · di-iitro-6-ooc-butylphcnol, g, -dinl ro-6 act omylphcnol, 2J, h-dinltro-6-me hylphenol, 2-methoxy-3,6-dichlorophenylacetlc acid, 2-methoxy-3,5,6-trichlorophenylacetlc acid, 2,3,6-tri-Chlorophenylacetlc acid, 3-mefchoxy-2,6-dichlorophenylacetic acid, 2-methoxy-5-chloro-6-methylphenylacetlc acid, 2-methoxy-3-nltro-5-chlorobenzolc acid.

Salts of the compounds of the formula of Group I, are quite suitable for use in this invention, particularly the alkali metal salts, the ammonium salts, the alk l-amlne salts in which the amine component is an unsubstituted alkyl amine of up to six carbon atoms and the alkanol amine salts in which the amine component is an unsubstituted alkanol amine of up to six carbon atoms; and where Y is other than -OH, the amides thereof, particularly the unsubstituted amides and the N-alkyl, N-alkoxy and N-alkoxy-N-alkyl amides in which the N-alkoxy and N-alkyl components contain up to ten carbon atoms, and the esters thereof, particularly esters in which the esterifylng group is an unsubstituted alkyl group of from one to ten carbon atoms.

For ease of formulation, the compounds of Group I are often employed in the form of their alkali metal salts, amine salts and ammonium salts, and in the case of the acids, in the form of their amides and esters, because these salts, 28850/ 2 in the form of their acids. These salts, amides and esters generally have activity equivalent to the corresponding acids or phenols. Examples of suitable alkali metal salts, ammonium salts, amine salts, amides and esters useful in the formulation of the herbicidal compositions of the present invention are: potassium 2-methoxy-3, 6-dichlorobenzoate, sodium 2-methoxy-3, 6-dichlorobenzoate, ammonium 2 -methoxy- 3, 6 -dichlorobenzoate, dim ethylarrine salt of 2-methoxy-3, 6-dichlorobenzoic acid, triethylamine salt of 2-methoxy-3, 6-dichlorobenzoic acid, ethanolamine salt of 2-methoxy 3,- 6-dichlorobenzoic ac id, diethanolamine salt of 2-ir ethoxy-3, 6-dichlorobenzoic acid, sodium 2 -methoxy- 3, 5, 6-trichlorobenzoate, potassium 2, 3, 6-tri-chlorobenzoate, sodium 2-methoxy-3, 6-dichlorophenylacetate, triethgtnolamine salt of 2, 3, 5, 6-tetrachlorobenzoic acid, N-alkoxy-2-methoxy-3, 6 -dichlorobenzamide, 2-methoxy-3, 6-dichloro benzamide, n-propyl 2-methoxy-3, 6-dichlorobenzoate, isopropyl 2-methoxy-3, 6-dichlorobenzoate, n-butyl 2-methoxy-3, 6-dichlorobenzoate, isooctyl 2 -m ethoxy-3, 6-dichlorobenzoate, potassium 2, 4-dinitro-6 -sec-butylphenoxide, sodium 2, 4-dinitro-6 -sec-butylphenoxide, ammonium 2, 4-dinitro-6-sec-butylphenoxide, ethanolamine 2, 4-dinitro-6-sec-butylphenoxide, isopropanol-amine 2, 4-dinitro-6 -sec-butylphenoxide, potassium 2, 4-dinitro-6 -sec-amylphenoxide, sodium 2, 4-dinitro-6-sec-amylphenoxide, ammonium 2, 4-dinitro-6-sec-amylphenoxide, ethanolamine 2, 4-dinitro-6-sec-amylphenoxide, isopropanol, 2, 4-dini tro-6-sec-amylphenoxide and the like. 28850/ 2 In a preferred embodiment of this invention the first compound is selected from the group consisting of compounds of formula (A) wherein A is selected from the group consisting of chlorine and unsubstituted lower alkyl groups, D is chlorine, E ia hydrogen, and R1, R and Z are as described above, and the alkali metal salts of the said compounds wherein R' is hydrogen.

In another preferred embodiment the second com pound is a compound of formula (I) wherein Y is COOH, Xg is hydrogen and X^, X^, X4 and X^ are independently selected from the group consisting of chlorine, bromine, methoxy, nitro, amino and two X3 hydrogen, provided a maximum of ©»€ Χ^, Χ^, Χ^ are and Xg e hydrogen; and the salts, amides and esters thereof. More preferably, the second com pound is selected from the group consisting of 2-methoxy-3, 6-dichlorobenzoic acid, 2-methoxy-3, 5, 6-trichlorobenzoic acid, their esters in which the esterifying group contains up to ten carbon atoms.their alkali metal salts, their amine salts in which the amino component contains up to ten carbon atoms, and their amices in which the amine component contains up to ten carbon atoms For practical use as herbicides, the combinations of active ingredients of this invention are generally incorporated into herbicidal compositions which comprise an inert carrier and a herbicidally toxic amount of the combination. Such herbicidal compositions, which can also be called formulations, enable the combination to be applied conveniently to the site of the weed infestation in any desired quantity. These compositions can be solids such as dusts, granules, or wettable powders; or they can be liquids such as solutions, aerosols, or emulsiflable concentrates.

For example, dusts can be prepared by grinding and blending the active compounds with a solid inert carrier suc as the talcs, clays, silicas, pyrophyllite, and the like.

Granular formulations can be prepared by impregnating the active compounds in the combination, usually dissolved in a suitable solvent, onto and into granulated carriers such as the attapulgites or the vermiculites, usually of a particle size range of from about 0.3 to 1.5 mm. or by coating an inert carrier with a wettable powder formulation of the combination. Wettable powders, which can be dispersed in water or oil to any desired concentration of the combination, can be prepared by incorporating wetting agents into concentrated dust compositions or by mixing the ingredients as in the case of the alkali metal salts of the active ingredients.

In some cases the active compounds in the combinations are sufficiently soluble in water or the common organic solvents such as kerosene or xylene so that they can be used tions of herbicides can be dispersed under superatmospheric pressure as aerosols. However, preferred liquid herbicidal compositions are emulsifiable concentrates, which comprise the combination according to this invention and as the inert car- rier, a solvent, and, in the case of an emulsifiable concentrate, an emulsifier. Such concentrates can be extended with water and/or oil to any desired concentration of the combination for application as sprays to the site of the weed infestation. The emulsifiers most commonly used in these concen-trates are nonionic or mixtures. of nonionic with anionic surface-active agents. With the use of some emulsifier systems an inverted emulsion (water in-oil) can be prepared for direct application to weed infestations.

The compositions of this invention can be applied as herbicides in any manner recognized by the art. One method for the control of weeds comprises contacting the locus of said weeds with a herbicidal composition comprising an inert carrier and as an essential active ingredient, in a quantity which is herbicidally toxic to said we,eds, a composition of the present invention. The concentration of the new compositions of this invention in the formulation will vary greatly with the type of formulation and the purpose for which it is designed, but generally the herbicidal compositions will comprise from about 0.05 to about 95 percent by weight of the ac-tive combinations of this invention. In a preferred embodiment of this invention, the herbicidal compositions will comprise from about 5 to about 75 percent by weight of the active combinations. The compositions can also comprise such additional substances as other pesticides, such as insecticides, nematocides, fungicides, and the like; stabilizers; spreaders; synergists; and the like.

Weeds are undesirable plants in their growing where they are not wanted, having' no economic value, and interfering with the production of cultivated crops or with the welfare of livestock. Many types of weeds are known, including annuals such as pigweed, lambsquarters, foxtail, crabgrass, wild mustard, field pennycress, ryegrass, goose-grass, chickweed, wild oats, velvet leaf, purselane, barnyard grass, knotweed, cocklebur, wild buckwheat, kochia, medic and smartweed, bi- ennials such as wild carrot, great burdock, mullien, round- leaved mallow, blue thistle, bull thistle, hounds -tongue, moth mullein, matricarla and purple star thistle; or perennials such as white cockle, dandelion, campanula, perennial ryegrass, quackgrass, Johnson grass, Canada thistle, hedge bind- weed, Bermuda grass, sheep sorrel, curly dock, nutgrass, field chickweed, and winter-cress. Similarly, such weeds can be classified as broadleaf or grassy weeds. It is economically desirable to control the growth of such weeds without damaging beneficial plants or livestock.

The new compositions of this invention are particularly valuable for weed control because they are toxic to many species and groups of weeds while they are relatively nontoxic to many beneficial plants. The exact amount of composition required will depend on a variety of factors, including the - hardiness of the particular weed species, weather, type of soil, method of application, the kind of beneficial plants in the same area, and the like. Thus, while the application of up to only about one or two ounces (about 28 or 56 grams) of the combination of active compounds per acre may be sufficient for good control of a- light infestation of weeds growing under ad or more of the combination of active compounds per acre may be required for good control of a dense infestation of hardy perennial weeds growing under favorable conditions.

Some typical herbicldal compositions of this inven-tion are shown in the following examples, in which all quantities given: are in parts by weight.

Example 1 Preparation of a Wettable Powder The following Ingredients are mixed thoroughly until a homogenous mixture is obtained. This powder is mixed with water immediately before application to give an aqueous solution containing the desired concentration of the combination of active compounds for use as a spray.

Potassium salt of N-methoxy-4-chloro-2- methylphenoxyacetamide 80 Potassium 2-methoxy-3 , 6-dichlorobenzoate 20 Example 2 Preparation of a Wettable Powder The foljlowing components are mixed intimately in con-ventional mixing or blending equipment and are then ground to a powder having an average particle size of Is ss than about 50 microns. The finished powder is dispersed in water to give the desired concentration of the combination of active compounds.

Sodium 2, 3 , 6-trichlorobenzoate 35 N-Methoxy -2-methy 1phenoxy/acetamide 40 Fuller's earth 22.75 Sodium lauryl sulfate 2 Methyl cellulose .25 Example 3 Preparation of a ettable Powder , The following components are mixed intimately in conventional mixing or blending equipment and are then ground to a desired particle size. Immediately prior to application the finished powder is dispersed in water to give the desired concentration of the combination of active compounds: N-methoxy - -methy 1 -4 - chlorophenoxyacetamlde 50 ' Dimethylamine salt of 2-methoxy-3, 6-dlchloro- benzoic acid 20 Puller's earth 25 Sodium lauryl sulfate 3 Methyl cellulose 2 Example 4 Preparation of a Wettable Powder The following components are mixed Intimately in conventional mixing or blending equipment and are then ground to a powder having an average particle size of less than about 50 microns. The finished powder is dispersed in water to give the desired concentration of the combination of active compounds .

Methyl S-methyl 2, 3, 5, 6-tetrachloro- monothioterephthalate 10 N-Methoxy-N-methy 1 -2-methy 1-4- chlorophenoxyacetamlde 15 Attapulgite 70.5 Colloidal silica 0.5 Oleic acid ester of sodium isethionate 2 Sulfonates of pine wood llgnln 2 Example 5 Preparation of an 011-dlspersible Powder The following components are blended and ground as described in the previous example to give a powder which. can be dispersed in oil to form a spray containing the desired concentration of the combination of active compounds.

N-Methoxy-N-methyl-4-chloro- 40 phenoxyacetamide 3,4-Dichloropropionanilide 30 Condensation product of diamyl- phenol with ethylene oxide , 4 Fuller 1 s- earth 26 Example 6 Preparation of a Dust The following ingredients are mixed thoroughly and then ground to an average particle size of less than about 50 microns to give a dust suitable for application with conventional dusting equipment.

-Methoxy -2-methy 1-4-chioro phenoxyacetamide 5 2-Methoxy-3 , 6-dichlorobenzolc acid 5 Talc 90 Example 7 Preparation of a Granular Formulation The following ingredients are mixed with sufficient water to form a paste, which is then extruded, dried, and ground to give granules, preferably from about 1/32 to £ inch ( .79 to 6.35 mm.) in diameter. The granules are applied with fertilizer spreader equipment or other conventional apparatus. The dextrin in this formulation serves as a binding agent.

Dimethylamine salt of 2-methoxy 3 , 6-dichlorobenzoic acid 5 N-Methoxy-N-methyl -2-methyl - - chiorophenoxyacetamide 5 Puller's earth 66 Dextrin 20 Sodium lignin sulfonate 3 Kerosene 1 The unexpected herbicldal activity of the comblna-tions of this invention was demonstrated by experiments carried out for the pre-emergence control of crabgrass. In these experiments small plastic greenhouse pots filled with dry soil were seeded with crabgrass. Twenty-four hours or less after seeding the pots were sprayed with water until the soil was wet and the test compounds formulated as aqueous emulsions of acetone solutions containing emulsifiers were sprayed at the indicated concentrations on the surface of the soil. After spraying, the soil containers were placed in the greenhouse and provided with supplementary heat as required and daily or more frequent watering. The plants were maintained under these conditions for a period of from 15 to 21 days at which time the condition of the plants and the degree of injury to the plants were rated on a scale of from 0 to 10, as follows: 0 - no injury, 1, 2 = slight injury, 3 ,4 = moderate injury, * 6 = moderately severe injury, 7* 8, 9 = severe injury and = death. The unusual effectiveness of these combinations as compared to the individual components are demonstrated by the results of these experiments as follows: Dosage Concn.

Test Actual Chemical Injury Compounds Compound Per Acre Rating DMA 1/5 J 8 Compound A 1/4 ) DMA 1/5 2 Compound A 1/4 3 .5 DMA = Dlmethylamlne salt of 2-methoxy-3, 6-dichlorobenzoic acid. Compound A = N-Methoxy'-2-methyl-4-chlorophenoxyacetamlde .

The combinations of the present invention are also unusually effective as herbicides as compared to other combinations of well known herbicides. For example in one experiment field tests were conducted for the control of campanula. In these tests the combinations listed below, in the form of aque-ous emulsions of acetone solutions containing emulsiflers, were sprayed at the indicated dosage on several plots containing the turf weed. Forty-two days after application, the plots were observed and the weed control as compared to untreated plots was recorded. Some of the results of these ex-periments are as follows: Test Dosage Percent Combinations Pounds/aere Control DMA 1/2 ) Compound A 1 ) 100 DMA 1 ) Compound A 1 ) 100 DMA 1/2 ) 2, 4-D 1 ) 0 2, 4-D 1 ) 2, 4, - 1 ) 0 2 , 4-D 2 50 DMA = Dlmethylamine salt of 2-methoxy-3 , 6-dichlorobenzolc acid. Compound A = N-Methoxy-2-methyl-4-chlorophenoxyacetamide .

The above test was repeated on plots containing sheep sorrel. The combinations of compounds listed below, formulated fiers, were sprayed st the Indicated concentrations on the plots. Thirty-two days after application, the plots were observed and the control of sheep sorrel rated on the scale: excellent control, slight control or no control. Presented in the table below are some of the results of these experiments; Test Dosage Combinations Pounds/acre Control DMA 1/4 Compound 1 Excellent DMA 1/2 Compound 1 DMA 1/2 2, 4-D 1 none 2, 4-D ■1 2 , , 5-T 1 none 2, 4-D slight DMA = Dimethylamlne salt of 2-methoxy-3 , 6-dichlorobenzoic acid. Compound A.= N-Methoxy-2-methyl-4-chlorophenoxyacetamide .

The compounds of Group A having formula A can be prepared by the reaction of the appropriate acyl halldes b the procedures detailed in United States Patents 3, 027, 407, 3, 166, 589, 3, 166, 591 and 3 , 168, 561.

The alkali metal salts of the compounds of Group A wherein R' in formula (A) is hydrogen and which are partlcular-ly useful as noted above, can be prepared from the corresponding N-alkoxy-appropriately ring substituted phenoxy alkylene amide by treating with an equimolar amount of alkali metal hydroxide and heating, if required. The reaction can be performed by heating, if required, in a solvent such as an alcohol or an alcohol-ketone mixture, for example, an ethanol and dl-oxane mixture. The desired salt can be recovered from the reaction mixture by evaporating the solvent, if used, by extraction, and the like. ft prepared is illustrated in the following examples: Preparation of o-Methylphenoxyacetyl Chloride A mixture of o-methylphenoxyacetic acid (27. g.;. 0.17 mole), thionyl chloride (13.8 ml.; 0.19 mole), and 125 ml. benzene was stirred and refluxed for about 7 hours in a 300-ml., ■ 3-neck flask fitted with a stirrer and condenser. An additional 5 ml. of thionyl chloride was added, and the mixture was stirred and refluxed for another 7 hours. The reaction mixture was filtered, and the filtrate was dried over magnesium sulfate. The drying agent was filtered off, and the solvent and excess thionyl chloride were distilled off under reduced pressure. The residue was distilled in vacuo to give 21.2 g. (70.6 of theory) of light yellow o-methylphenoxyacetyl chloride, b.p. 62°/0.1 mm.

Preparation of N- ethoxy-N-methyl-2-methylphenoxyacetamide A 300-ml., 3-neck flask fitted with a stirrer, reflux condenser, and addition funnel was charged with potassium carbonate (l4.9 g.; 0.108 mole), Ο,Ν-dimethylhydroxylamine hydrochloride (9.6 g.; Ο.Ο98 jnole), and 100 ml. benzene. Water (10 ml.) was added slowly, after which o-methylphenoxyacetyl chloride (18 g.j Ο.Ο98 mole) was added slowly as the effervescence permitted. The reaction mixture was stirred and refluxed for about 7 hours and filtered. The filter cake was washed thrice with benzene, and the combined filtrate and washings were dried over magnesium sulfate and filtered. The benzene was distilled off under reduced pressure. The residue was distilled in vacuo to give 14.9 ,g.. (72. $ of theory) of colorless N-methoxy- -methyl-2-methylphenoxyacetamide, b.p. 115-ll8°/0.4 mm.: A cut b.p. 117°/0.4 mm. was taken for analysis: Analysis for C-^H-^NO^: Preparation of the Potassium Salt of N-methoxy-4-chloro- 2-methylphenoxyacetamide A solution of N-methoxy-4-chloro-2-methylphenoxy--1 acetamide (15.2 g. j 0.066 mole) in dioxan (50 ml.) and 90 potassium hydroxide (4.1 g. j 0.066 mole) in absolute ethanol (30 ml.) was placed in a 250 ml. three-necked flask fitted with a stirrer and condenser with a calcium chloride tube.

The reaction mixture was stirred and heated ar reflux temperature for 6½ hours. The mixture was then evaporated in a rotary evaporator to yield a yellow-brown amorphous ^olld. This solid was taken up in ether. The ether solution was dried over magnesium sulfate, filtered and evaporated on a steam bath to yield a solid which was air-dried, jand again treated with ether. The solid did not dissolve and the suspension was filtered. The white solid obtained was the potassium salt of N-methoxy -4-chloro-2-methylphenoxyacetamide .

The compounds of Formula I used in this invention as described above, can be readily prepared for example, by the reaction of the appropriately substituted phenoxy alkanoyl halide with an appropriate N-alkoxyamine or N-alkyl-N-alkoxy- amine. The acyl halides suitable as starting materials are either known in the art or can be prepared readily from the corresponding carboxylic acids by reaction with halogenating agents such as thionyl chloride or phosphorus pentachloride .

Dimethyl 2, 3., 5j 6-tetrachloroterephthalate is known to the art, while the other compounds of Group V can be readily prepared by reacting a half alkyl ester-half acid or half alkyl ester acyl halide of 2 ,3 , , 6-tetrahaloterephthalate wherein the alkyl group contains from 1 to 3 carbon atoms, with an alcohol containing 1 to 3 carbon atoms selected so that the said compound contains exactly only one carbomethoxy t group.

More particularly the half acid, end preferably the acyl halide thereof, is heated with the desired alcohol preferably at reflux and in the presence of a base such as pyridine for at least several hours. Alternatively, the half alkyl ester-half acid or a salt thereof, preferably dissolved in a suitable solvent, can be reacted with an alkylating agent, such as an alkyl halide or an alkyl sulfate, such as dimethyl sulfate, diethyl sulfate or dipropyl sulfate, to obtain the desired product. Thei salt of the half alkyl ester-half acid can be prepared by dissolving the half ester-half acid in an aqueous solution of base.

The half-ester-half acyl halide can be obtained by halogenating the half ester-half acid, conveniently with a chlorinating agent such as thlonyl chloride at the reflux temperature of the solvent, if a solvent is used. The acyl chloride can be recovered from the reaction mixture by removing the chlorinating agent, for example by heating in vacuo. The half alkyl ester-half acid can be prepared by partial hydrol-ysls of the corresponding dlalkyl 2,3,5,6-tetrahaloterephthal-ate with an alkali metal hydroxide such as potassium hydroxide.

Claims (6)

1. 28850/2 1. A herbicidal composition which comprises a first compound selected from compounds of the formula: wherein A and D are independently selected from the group consisting of hydrogen, chlorine, and lower alkyl groups; provided that a maximum of one of A and D is hydrogen, A is chlorine only when D is chlorine; R' is selected from the group consisting of hydrogen and alkyl groups; R is an alkyl group; and Z is an unsubstituted alkylene group containing from one to four carbon atoms; and the alkali me tal salts of the said compounds wherein R1 is hydrogen; and at least one second compound selected from the group consisting of {I) compounds of the formula: Y wherein Xj, X2, X3, X4 and Xg are independently selected from the group consisting of halogen, lower alkyl, lower alkoxy, and hydrogen provided a maximum of two of Xj, Xg, X3, X4 and Xg are hydrogen; and Y is selected from the group consisting of (CH2)nCOOH and -COOH wherein n-is an integer from one to three; and the salts, amides and esters thereof.

2. The composition of claim 1, wherein A is selected from the group consisting of chlorine and lower alkyl groups and D is chlorine.

3. The composition of claim 1 or 2, wherein the second compound is a herbicidally active compound of the formula of group I wherein Y is -COOH, Xg is H and Xi, X2, X4 and X& are independently selected from 28850/2 the group consisting of chlorine, bromine, methoxy and hydrogen provided a maximum of one of Xj^ Xg» X4 and Xg is hydrogen and the salts, amides and esters thereof.

4. The composition of claim 1, wherein the second compound is selected from the group consisting of 2-methoxy-3, 6-dichlorobenzoic acid, 2-methoxy-3, 5, 6-trichlorobenzoic acid, their esters in which the esterifying group contains up to ten carbon atoms; their alkali metal salts, their amine salts in which the amine component contains up to ten carbon atoms, and their amides in which the amine component contains up to ten carbon atoms.

5. The composition of claim 1, wherein the first compound is an alkali metal salt of N-methoxy-2-methyl-4-chlorophenoxyaeetamide and the second compound is an alkali metal salt of 2-methoxy-3, 6-dichlorobenzoic acid. the first compound is N- and the second compound or the dimethylamine salt of 2-methoxy-3, -dichlorobenzo c aci . 7. A herbicidal composition comprising an inert carrier and a herbicidally toxic amount of a composition of any of claims 1 to

6. 8. A herbicidal composition according to claim 1 substantially s herein described with particular reference to any one of the specific examples. 9. A method of destroying undesirable plants Which comprises, contacting said plants with a herbicidal composition as defined in any of claims 1 to 8, in a quantity which is injurious to said plants. Agents for Applicants