CA1183149A - Herbicidal compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Compounds of the formula (I) wherein R is halogen, (C1-C4)alkyl, halo-(C1-C4)alkyl, (C1-C4)alkoxy, halo(C1-C4)alkoxy, phenyl, -NO2, -NH2 or -CN;
R' is (C1-C4)alkyl or halogen;
n is an integer of from 1 to 3 with the proviso that, if R is halogen and n is 1, R occupies the ortho- or meta- position in the phenyl ring;
n1 is zero or an integer of from 1 to 3;
Y is (C1-C6)alkylene and X is -COOH, -COO-(C1-C8)alkyl, -CONH2, -CONH-NH2, -CN or -COO-Cat, "Cat" being the cation of an inorganic or organic base, are useful as selective grass herbicides.

Description

s~

This invention relates to novel benzyl-phenoxyalk~lecarboxylic acids useful as herbicides. Related compounds are the subject of our copending application Serial No. 22~,168, filed April 9, 1975, of which the present application is a divisional.
The present invention provides benzyl-phenoxyaLkanecarboxylic acids and the derivatives thereof corresponding to the formula ~ I
R~n) (nl) wherein R is halogen, ~Cl-C4)alkyl, halo-~Cl-C4)alkyl, (Cl-C4)alkoxy, halo-(Cl-C4)alkoxy, phenyl, -N02, -NH2 or -CN;
R' is (Cl-C4)alkyl or halogen;
n is an integer of from l to 3 with the proviso that, if R is halogen and n is 1, R occupies the ortho- or meta- position in the phenyl ring;
nl is zero or an integer of from 1 to 3;
Y is (Cl-C6)alkylene and X is -COOH, -COO-(Cl-C8)alkyl, -CONH2, -CONH-NH2, -CN or -COO-Cat, "Cat" being the cation of an inorganic or organic base.
In the above formula I, R is preferably halogen, especially chlorine or bromine in the 2,4-position, nl is preferably zero, that is, the right hand benzene ring is preferably unsubstituted, but may also be substituted by Cl or CH3, nl in this case preferably being 1. The radical -O-Y-X is preferably in ortho- or para-position, and especially in para-position, to the benzyl radical. Y represents a`bove all the radical -CH(CH3)-. In the case where X

- 1 - ~

is a carboxylic ester group, this group contains prefe-rably from 1 to ~ carbon atoms. "Cat" stands preferably for an alkali or alkaline ear-th metal ca-tion, especially Na , K or Ca /2.
The benzylphenoxy-alkanecarboxylic acids and the derivatives thereof corresponding to the formula I are prepared according to known rnethods J for example by reacting benzylphenols of the formula - C~2 - ~ OH II

(nl) with halocarboxylic acid derivatives of the formula Hal-Y-X III
where Hal is chlorine or bromine and X is -COO-(Cl-C8)alkyl, -CONH2, -CONH-Nll2 or -CN.
The reaction is generally carried out in an inert organic solvent such as methanol, ethanol, benzene, petroleum ether, diethylketone, dioxan, DMF or DMSO in the presence of an approximately stoichiometric amount of an inorganic or organic base such as NaOH, KOH, K2CO3, Na2CO3, pyridine or triethylamine, at temperatures of from 50 to 150C, preferably from 80 to 120C.
Subsequently, the free carboxylic acids or the salts thereof may be prepared also in known manner from the reaction products obtained, preferably by saponification of the esters or nitriles.
The starting products of formula II are obtained according to known methods, for example by reaction of a correspondingly substituted benzyl chloride with a phenol in the presence of a condensation agent such as AlC13 or ZnC13 (Ind. Eng. Chem. 28 505 (1936)). In this reaction, benzyl phenols substituted both in o- and p-position are obtained, which may be separated by Eractional dis~:illation.
The compoullds of formula I have an excellent selective activity against weed grasses. In pre-emergence as well as in post-emergence treatment, such weed grasses are destroyed at low doses, while even considerable overdoses do not or only insigniflcantly damage broad-leaved (dicotyledonous) crop plants and broad-leaved weeds.
Surprisingly, various crop plants from the botanic species of grasses, for example rice, barley, wheat, sorghum, are not damaged by the compounds of the invention at a dosage sufficient to destroy weed grasses.
The compounds may therefore be used for combating weed grasses in cereals as wel] as in dicotyledonous crop plants such as sugar beet, leguminosae, cotton, vegetables, cucumber species, tomatoes/ tobacco etc.
The herbicidal activi.ty is especially pronolmced against foxtail grass, wild oat, barnyard grass, foxtail millet, and crabgrass. The compounds may be used before or after the emergence of the plants which is not possible with known herbicides for the selective destruction of weed grasses. Trichloro-acetic acid, alachlor ~2-chloro-2,6-diethyl-N-(methoxymethyl)-acetanilide) and trifluralin (N,N-di-(n-propyl)-2,6-dinitro-4-trifluoromethylaniline) for example can be used only in pre-emergence treatment; barban (4-chloro-2-butinyl-N-(3-chlorophenyl)-carbama~e) or chlorophenpropmethyl (2-chloro-3-(4-chloro-phenyl)-propionic acid methyl ester) only in post-emergence treatment.
Furthermore, the concentrations required for complete destruction of the weed grasses are considerably lower than with the cited herbicides.
The compounds of the invention may be used in usual formulations, for example as wettable powders, emulsifiable concentrates, sprayable solutions, dusting powders or granules.
Wettable powders are preparations which are homogeneously dispersible in water, and which, in addition to the active ingredient and a diluent or :iner-t substance, contain also wetting agents, for example yolyoxethylated alkylphenols, polyoxethylated oleyl or stearyl amines, or alkyl or alkylphenyl-sulfonates, and dispersing agents, for example the sodium salts of lignin-sulfonic acid, 2,2'-dinaphthyl-methane-6,6'-disulfonic acid, dibutyl-naphthalene-sulfonic acid.
Emulsifiable concentrates may be obtained by dissolving the active ingredient in an organic solvent, for example cyclohexanone, xylene, or higher boiling aromatics. In order to obtain a good emulsion in water, further emulsifiers may be added.
Dusting powders are obtained by grinding the active ingredient with finely divided solid substances, for example talcum or natural aluminates, for example kaolin, bentonite, pyrophyllite or diatomaceuous earth.
Spraying solutions, commercially available as aerosol sprays, contain the ac~ive ingredient dissolved in an organic solvent, and a propellant, for example a mixture of hydrocarbon fluorides.
Granules may be obtained either by atomi~ing the active ingredient through a nozzle onto an absorptive granulated inert materical, or by applying a concentrate of the active ingredient by means of an adhesive, for example polyvinyl alcohol, the sodium salt of polyacrylic acid or mineral oils, onto the surface of a carrier, for example, sand, kaolinites or granulated inert materials. The active substances may also be granulated by the methods used in the preparation of fertilizer granulated material, if desired in admixture with one or more fertilizers.
The concentration of the active substances of the present invention in commercial herbicidal formulations may vary considerably. For example, in wettable powders, the concentration of active ingredient may vary within the range of from about lO % to 50 % the remaining amount consisting of the above mentioned Formulation additives. In emulsifiable concentrates, the concentra-tion of active ingredient may vary in the range of from about 10 % to 50 %. Dusting powders generally contain from 5 to 20 % and spray solutions from about 3 to 20 % of active ingredient. In the case of granules, the content of active ingredient par~ially depends on whether the active compound is liquid or solid and on what granulating agents, fillers and other additives are used. It is generally from 3 to 10 %.
For practical applications, the commercial concen~rates are optionally diluted in usual manner~ for example, in the case of wettable powders and emulsifiable concentrates, by means of water. Dust formulations, granulated preparations and spray solutions are not diluted any more before their application. The amount of active ingredient required for application varies within wide limits in accordance with the external conditions, for example temperature and moisture; generally from 0.1 to 10.0 kg/ha, preferably from 0.2 to 2.5 kg/ha, of active substances are used.
Examples of formulation:
Wettable powder consisting of 10 - 40 weight % of active substance 30 - 40 weight % of finely dispersed adsorptive silicic acid 8 " " " sodium salt of dinaphthylmethane-disulfonic acid (TamolR NNO)

2 t, I~ 1l sodium salt of alkylnaphthalenesulfonic acid (LeonilR DB) 0.5 " " " sodium salt of oleylmethyltauride ~HostaponR T) remainder kieselguhr.
Emulsifiable concentrate consisting of .. . . .. _ _ 20 - 50 weight % of active substance, 5 weight % of calcium salt of dodecylbenzenesulfonic acid 7 " " " nonylphenol-polyglycol ether

3 " " " oleylalcohol-polyglycol ether remainder xylene.
Granwled material consisting of 3 - 5 weight % of active substance 2 " " " emulsifier mixture of calci~n salt of dodecylbenzenesulfonic acid and castor oil-polyglycol ether / or ester " " " kieselguhr or finely dispersed silicic acid remainder quartz sand (0.3 to 1 mm 0).
The novel herbicides may also be combined with known herbicides, for example with the following substances cited by their common names:
Urea derivatives: linuron, monolinuron, chlorotoluron, ipuron, diuron, metoxuron, fluo-meturon, methabenzthiazuron;
Triazine derivatives: simazine, atrazine, ametryne, prometryne, desmetryne, methopro-tryne, metribuzine;
Uracil derivatives: lenacil, bromacil;
Pyrazon derivatives: pyrazone;
Phenoxy-alkanecarboxylic acids: 2,4-D, MCPA, dichloroprop, meco-prop, 2,~-DP, TBA;
Carbamic acid derivatives: barban, phenmedipham, diallate, triallate, vernolate, benthiocarb, Swep;
Dinitrophenol derivatives: dinitro-o-cresol, dinoseb, ~DNBP), dinoterb, and the esters or salts thereof;

Chlorinated allphatic acids: TCA, dalapon;
Amides: diphenamide, isocarbamide;
Dipyridilium derivatives: paraquat, diquat;
Anilides: propanil, solane, monalide, alachlor, propachlor, bentachlor;
Anilines: trifluraline, nitral:ine, oryzaline, dinitramine;
Other active substances: dichlobenil, ioxynil, cyanazine, pyrazone, bromofenoximJ chloro-thalmethyl, benzoylpropethyl, chlorophenpropmethyl, MSMA, DSMA, nitrofen, flurenol, bentazol, fluorodifen.
The following examples illustrate the invention and related compounds.
Examples of~ ion E X A M P L E 1:
_ . _ 2rp-~4-chlorobenzyl)-phenoxi~-propionic acid ethyl ester.
A solution of 22 g of 4-(4-chlorobenzyl)-phenol and 18.5 g of ~-bromopropionic acid ethyl ester in 100 ml of dimethyl formamide was stirred for 2 hours at 100C together with 16 g of potassium carbonate. After cooling, the reaction mixture was poured into 1 liter of water. ~n oil precipitated which was separated and dried over sodium sulfate. By means of vacuum distillation, 23.3 g of 2-rp-(4-chlorobenzyl)-phenoxi7-propionic acid ethyl ester were obtained.
b.p.: 146 - 151C/0.1 mm Hg/nD22: 1.5527 Cl ~ CH2 { O ~ O-IH-COOC2H5 3i E X A M P L E 2:
.
2-~-(2,4-dichlorobenzyl)-phenoxi7-propionic acid amide.
A solution of 25.3 g of 4-(2,4-dichlorobenzyl)-phenol and 15.2 g of ~-bromopropion:i.c acid amide in 100 ml of dimethyl formamide was stirred for 2 hours at 100C together with 16 g of potassium carbonate. After cooling, the reaction mixture was poured into 1 liter of water. A viscous oil precipitated which was absorbed in methylene chlorlde and washed with water.
~:Eter drying over sodium sultate, the solvent was distilled aff under reduced pressure. The remaining colorless crystals were recrystallized from methanol.
Yield: 25.8 g; melting point 148 - 149C.

Cl ~ CH2 ~ O-CH-CON~I~

E X ~ M P L E 3:
Sodium salt of 2-~ 2,4-dichlorobenzyl)-phenox~7-propionic acid.
- 17.5 g of 2- E-(2,4-dichlorobenzyl)-phenox_7-propionic acid ethyl ester were stirred with 100 ml of methanol and a solution of 2.5 g of caustic soda in 100 ml of water for 3.5 hours at 50C, and then abandoned overnight at room temperature. The solvent was distilled off under reduced pressure, and the remaining sodium salt was dried at 60C under reduced pressure.
19.6 g of sodium salt of 2- ~ -(2,4-dichlorobenzyl)-phenoxi7-propionic acid were obtained.

Cl ~ ~- CH2 ~ O-CII-COONa Cl CH3 E X A M P L_E 4:
2- ~ -(2,4-dichlorohenzyl)-phenoxi~7-butyric acid ethyl ester.

:llB3~ 91 A sol~t:ion of 25.3 g of ~-(2,4-dichlorobenzyl)-phenol and 15 g of ~--chlorobutyric acid ethyl ester in 100 ml of dimethyl formamide were stirred for 2 hours at 100C with 16 g of potassium carbonate. After cooling, the reaction mixture was poured into 1 liter of water. An oil precipitated which was separated and dried over sodium sulfate. By vacuum distillation, 16.8 g of 2-L~-(2,4-diclllorobenzyl)-phenoxV-butyric acid ethyl ester were obtained.
b.p.: 180 - lS3C/0.8 mm Hg/nD21: 1.5912 Cl ~ Cll2 _ ~ _ O-CH-COOC2H5 The following compounds were prepared according to the methods described in the a~ove Examples.

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E X A M P L, E 33:
-2-Lp-~2,4-clichloroberl~yl~-phenoxi7-propionic acid.
17.5 g of 2- ~-(2,4-dichlorobenæyl)-phenox_7-propionic acid ethyl ester were refluxed for 2 hours with a soliltion of 2.5 g of caustic soda in 100 ml of methanol. After cooling, 100 ml of water were added and the mixture was acid-ified with 2n hydrochloric acid. The propionic acid liberated precipitated in the form of a colorless oil which, on cooling in icewater, solidified to become a colorless wax-like mass. The yield is 15.3 g.

~ ~ } CH3 Biological Examples E X A M P L E I:

-Seeds of ~eeds belonglng to different botanic families were sown in po~s and covered with earth. The same day, the earth was sprayed with wettable powder formulations ~uspended in water of the compound of Example 5; in similar manner, the known substance dichloropropL~-(2',4'-dichlorophenoxy)-propionic acid7 was used as comparative agent. In a further test, both the cited sub-stances were sprayed onto plants already emerged and having developed 2 to 3 leaves.
The results Cand also the results of all following tables~ were evaluated according to the following scheme in degree of damage in per cent:

p rlumber weeds c~op plants _ ~_ .... ... __ _ _ 2 97.5 to 100 0 to 2.5 3 95.0 ~o 97.5 2.5 to 5.0

4 90.0 to 95.0 5.0 to10.0 85.0 to go.o 10.0 to15.0 6 75.0 to 85.0 15.0 to25.0 7 65.0 to 75.0 25.0 to35.0 8 32.5 to 65.0 35.0 to67.5 9 ~ 0 to 32.5 67.5 to lO0 ln this schema number 4 is still considered an acceptable herbicidal effect tn weeds and satisfactory preserving effect in crop plan-ts (cf. Bolle ~achrichten-blatt des Deutschen Pflanæenschut~dienstes 16 1964, pages 92 - 94).
The results o~ t~e following Table I show~that the compound of the invention, contrary to dichloroprop, is not or nearly not active against broad-leaved weeds, even at a high dosage rate of 2.5 kg/ha. Its special activity is limited to species of the family of grasses~ as demonstrated by the example Lolium, Alopecurus and Echinochloa. Dichloroprop, Oll the other hand, shows no actlvîty against the cited species and other grasses, which proves that the substanres ~ the invention have a completely different activity spectrum than the known growth herbicides of the dichloroprop type, although being of similar chemical structllre.
Table I
Activity against ~eeds and weed grasses; pot test in a greenhouse; dosage rate:
2,5 kg/ha of A.S. (=active substance) plant species pre~emergence treatment, post-emergence treatment product of dichloroprop product of dichloroprop Example 5 Example 5 _ _ . _ ,.. ~
A. ~eeds ~dicotyledonous species~
Galium ;~ 2 9 Matricaria 8 5 8 ~
Ipomoea 9 2 9 3 Sinapis 9 1 8 Amaranthus 6 l 7 B. Weed grasses (monocotyledonous species) Lolium 1 9 4 9 Alopecurus 2 9 2 9 Echinochloa 1 E X A M P L E II:
Seeds of w~eat, barley, Eoxtail grass (Alopecurus myosuroides~ and wild oat ~avena fa~ua~ were sown in pots and allowed to emerge in a greenhouse;
after having developed 3 to 4 leaves they were sprayed with aqueous suspensions o~ substances of the invention. As comparative agent, the commercially avail-able compound chlorophenpropmethyl was used.
~ \ CH
Cl ~ ~ CH2-C~-COOCH3 The resu.lts listed in Table II sllow that 4 weeks after the treatment, foxtail grass and wild oat were substantlally destroyed by the compounds of the inventlon, alread~ at lo~ dosage rates o~, for examp].e, 0.62 kg/ha, whi.le the crop plants were not or onl~ very slightly damaged. Chlorophenpropmethyl, on the other hand, damaged wild oat only slightly at the high dosage rate of 1.25 kg~ha~ while Eoxtail grass remaîned entirely undamaged.
Table II
Pot test ~n t~e greenhouse; yost-emergence treatment dosage rates in kg/ha of A.S.

plant spec~es Chlorophenpropm~ethyl product according to Example 1.25 0.62 . No- 5 No. 7 1.25 0.62 1.25 0.62 ~ __ _ _ A. ~ed grasses Alopecurus 9 9 1 1 1 myosuraides Avena fatua 4 8 1 2 3 4 B. Crop plants ~eat 1 1 1 1 1 Barley _ __ 4 2 2 The compounds of Examples 18, 1~, 30 and 31 had a similar activity as those of Examples 5 and 7.
E X A M P L E_ ~II
Barnyard grass (Echinochloa) is one of the most important weeds in rice cultures of rice cultivating countries, both when the rice is directly sown as well as when it i5 reared in plant nurseries and then transplanted. The two following te~ts A and B prove that the substances of the invention are most suitable for combating barnyard grass in rice planted according to both culti-vating methods.

~JL~

In tes~ A, barnyard grass and rice were sown in pots simultaneously.
AEter the plants had developed 3 to ~ leaves, the in~ention compounds in the form of aqueous suspensions were sprayed onto the plants. The result indicated in Table III (4 weeks after the treatment~ shows that the lowest dosage rate (0.31 kg/ha of active substance2 of all substances is sufficient ~o combat the barnyard grass; a double dosage of substances oE the invention does not seriously damage the rice.
In test B, 3 weeks old rice plants were transplanted into pots and simultaneously, barnyard grass was sown. A few days later, when the barnyard grass began to emerge, the pots were ~looded, and the invention compounds were added to the stagnant water. The results obtained 4 weeks after the treatment are shown in Table III.
Table III
Test in flooded pots in the greenhouse; dosage rates in kglha of A.S.

plant species products of Examples No. 5 No. 7 0.~20.31 0.62 0.31 Test A
Simultaneous sowing of Echinochloa and rice, Treatment: spraying after emer&ence Echinochloa 1 3 1 2 rice 2 1 2 Test B

Sowing of Echinochloa at the time of transplanting the rice Treatment: Addition of the products to the stagnant water Echinochloa 2 2 1 4 rice _ _ i 1 _ I 1 1 E ~ ~ M P L E IV
~ _ . . . _.
In regions where there i8 a crop rotation of soybeans after corn (~or example în wide areas of the United States of America~, volunteer corn in soy-beans îs a serious problem. In order to test ~hether substances of the inven-tion are suitable for combating corn in soybeans, corn and soybeans were sown in pots and, after emergence, treated with aqueous suspensions of substances of the inventionO (See Table IV). The results listed in Table IV show that the compounds of the învention used for this purpose destroy the undesirable corn plants without damaging the soybeans.

lo Table IV
Pot test in the greenhouse; post-emergence treatment dosage rate: 2,5 kg/ha of A.S.

Plant species product of Exa~ples No. 5 No. 19 No. 18 No. 7 _ A. ~eed grasses Zea mays 1 ` 3 3 4 B. Crop plant S`~ybean E X A M P L E V:
In a further test, seeds of the barnyard grass CEchinochloa~ and fox-tail millet CSetarla) as well as of sorghum and cotton were sown. After emergence, the plants were sprayed with aqueous suspensions of substances of the invention Csee Table V~.
The results show that substances of the învention, at dosage rates of 0.31 and 0.62 kg/ha, have a good to very good destructive effect on the cited weed grasses withou~ da~aglng sorghum and COttOII.

Table V

Pot test in the greenhouse; post-emergence treatment dosage rates in kg/ha of A.S.

Plant species product of Rxamples No. 5 No. 7 0.62 ~.31 0.62 0.31 ~ __ A. ~eed grasses Echinochloa 1 2 1 Setaria 1 3 1 5 B. Crop plant Sorghum vulgare 2 1 2 .. 1 1 1 .

E X A M P L E Va:
Compounds 5 and 7 were sprayed in form of a~ueous suspensions at a dosage rate oE 2.5 kg/ha of active substance onto a number of crop plants in the stage of 2 to 3 leaves. The following species were not damaged: sugar beet, common beet, spinach, cucumber, sugar melon, water melon, red clover, lucerne, lQ peanut9 soybean, dwarf-bush bean, pea, horse bean, ~lax, carrot, celery, rape, cabbage, tomatoe, tobacco, potatoe, cotton. This test proves that substances of the invention may be used in dicotyledonous crop plants even at high dosage rates without a risk for the crop plants.
_ X A M P L E Vl:
Seeds of crabgrass ~Digitarla~, wild oat (Echinochloa~ and ~oxtail millet (Setaria~, as well as oE sorghum were sown in pots. The same day, sub-stances oE the invention in the form of aqueous suspensions were sprayed at different dosage rates on the soil surface (pre-emergence treatment). The result indicated in Table VI shows that substances o~ the lnvention, at dosage rates oE
0.31 or 0.62 kg/ha, destroy the cited weed grasses, and that they do not damage substantially the sorghum at the same time, nor when they are used in a high concentratlon oE 1.25 kg/ha. The comparative agent, that i5, commer~ial alachlor N ~ 2 3 \,~( C-cH

generally used in the agricultral practice for combating grasses in the pre-emergence treatment with very good success damaged the sorghum to such an extent that it practically cannot be used in this crop plant. The comparative agent propachlor 1~ ~ CH~CH312 C-CH2Cl o also a kno~n commercial herbicide, had to be used at a much higher dosage rate;
e~en at 1.25 kg/ha, the weed grasses ~ere not completely destroyed.
E X A_M P L E VII:
In a similar test, two substances of the invention were examined ~or their action against foxtail grass (Alopecurus2 in cereals. The result indicated in Table VII proves that both these substances are suitable for selectively combating foxtail grass in cereals.

E X A ~I P L E VIII:
In further tests, seeds o~ the weed grasses listed in Table VIII were sown in pots, and subsequently, the earth was sprayed with an aqueous suspension of the compound o~ Example 1. The damage values cited in Table VIII were obtained 4 weeks after the application. 'Che data show that the subs~ances of th~
invention have a good herbicidal activity against the weed grasses used in the test, that is, foxtail grass (Alopecurus), foxtail millet (Setaria), meadow-grass (Poa spec.), ray-grass (Lolium) and barnyard grass.

Table VI
Pot test in the greenhouse; pre-emergence treatment; dosage rates in kg/ha of A.S.

plant specîesPropachlor Alachlor product of Example ~o. 5 1.25 1.25 0.62 0.31 1.25 0.620.31 A. ~eed grasses Digitaria 4 1 1 1 1 1 2 Echînochloa 2 1 1 2 1 3 4 Setaria 6 3 5 7 1 1 4 B. Crop plant Sorghum 8 7 ~ 2 Table UII
Pot test in the greenhous; pre-emergence treatment; dosage rates in kg/ha of A.S.
Plant species product of Example - No. 5 1.250.62 0.31 .____ A. Weed grass Alopecurus ~L 2 4 B. Crop plant Autumn wheat 2 1 Autumn barley 3 1 Table VIII
Pot test in th~ greenhouse; pre-emergence treatment; dosage rate 2,5 kg/ha of A.S.
Weed grasses product of Example 1 . . _ _ Alopecurus 3 Setaria 3 Poa spec. 2 Lolium 4 Echinochloa The compounds of Examples (62, (82, (13~, C232, C22, ~32, ~262 a~d (292 had a similar effect.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A benzyl-phenoxyalkanecarboxylic acid or a derivative thereof corres-ponding to the formula:
(I) wherein R is halogen, (C1-C4)alkyl, halo-(C1-C4)alkyl, (C1-C4)alkoxy, halo-(C1-C4)alkoxy, phenyl, -NO2, -NH2 or -CN;
R' is (C1-C4)alkyl or halogen;
n is an integer of from 1 to 3, with the proviso that, if R is halogen and n is 1, R occupies the ortho- or meta- position of the phenyl ring;
n1 is zero or an integer of from 1 to 3;
Y is (C1-C6)alkylene and X is -COOH- -COO-(C1-C8)alkyl, -CONH2, -CONH-NH2, -CN or -COO-Cat, "Cat" being the cation of an inorganic or organic base.

2. A compound of claim 1, in which the group -O-Y-X is in the para-position on the benzyl group.

3. The compound

4. The compound

5. The compound

6. The compound

7. The compound

8. A process for the preparation of a compound of formula I as defined in claim 1, which comprises reacting a benzylphenol of the formula (II) wherein R, R1, n and n1 are as defined in claim 1, with a halocarboxylic acid derivative of the formula Hal-Y-X (III) where Hal is chlorine or bromine, X is -COO-(C1-C8)-alkyl, -CONH2, -CONH-NH2 or -CN, and Y is as defined in claim 1; and if desired converting a resulting ester to a corresponding acid or salt.

9. A process for selectively combating weed grasses in crop plants, which comprises applying to the crop plant to be treated an active amount of a compound of the formula (I) wherein R is halogen, (C1-C4)alkyl, halo-(C1-C42alkyl, (C1-C4)alkoxy, halo-(C1-C4)alkoxy, phenyl, -NO2, NH2 or -CN;
R' is (C1-C4)alkyl or halogen;
n is an integer of from 1 to 3, with the proviso that, if R is halogen and n is 1, R occupies the ortho- or meta- position of the phenyl ring;
Y is (C1-C6)alkylene and X is -COOH, -COO-(C1-C8)alkyl, -CONH2, -CONH-NH2, -CN or -COO-Cat, "Cat" being the cation of an inorganic or organic base.