the compounds of formula ( i ) may be prepared by reacting a substituted alkylnitrile of the formula ## str3 ## wherein r and n are as defined above , and a can be halogen , mesylate , tosylate or other aryl sulfonates , with a quinoxalinyloxyphenol of the formula ## str4 ## wherein r 1 is as defined above . the reaction is typically conducted in nonaqueous solution in the presence of an inorganic base ( such as sodium carbonate , potassium carbonate or potassium hydroxide ) at suitable temperature . according to the present process , the compounds may be applied in the form of agriculturally effective compositions . the compositions are comprised of ( a ) an herbicidally effective amount of a compound of formula ( i ) as an active ingredient , and ( b ) an agriculturally acceptable carrier such compositions may comprise one or more active compounds to prepare the compositions , the active compound may be mixed with an adjuvant to provide compositions in the form of finely - divided particulate solids , granules , pellets , wettable powders , flowable liquids , soluble powders , solutions , and aqueous or organic solvent dispersions or emulsions . such formulations may be of several different physical and chemical types , and of which could be made by one familiar with the art . for instance , the agriculturally active compound may be impregnated on finely - divided or granular inorganic or organic carriers such as appapulgite clay , sand , vermiculite , corn cob , activated carbon or other granular carriers known to the art . the impregnated granules may then be spread on the soil or incorporated into the soil . alternatively , the chemical may be formulated as a wettable powder by grinding it into a fine powder and mixing it with an inactive powdered carrier to which a surface active dispersing agent has been added . typical powdered solid carriers are the various mineral silicates ( such as mica , talc , pyrophyllite , clays and the like ) or powdered organic materials ( e . g ., corn cob ). the wettable powder may then be dispersed in water and sprayed on the soil surface , or on crop or weed plants . similarly , an emulsifiable concentrate may be prepared by dissolving the chemical in a solvent such as naphtha , toluene , or other aromatic or aliphatic hydrocarbon to which a surface active dispersing agent generally has been added the emulsifiable concentrate may then be dispersed in water and applied by spraying . the concentration of active chemical in the composition may vary widely typically ranging from about 1 % to about 95 % by weight . the concentration of active chemical in dispersions applied to the soil or foliage is typically between about 0 . 002 % and about 80 % by weight . formulations containing the active ingredient ( s ) may be dispersed in water or an organic liquid ( such as oil ) and applied to target plants . surface active agents may be added to the applied solution to increase its qualitative or quantitive range of activity . suitable surface active agents are well known to those skilled in the art . reference may be made to mccutcheon &# 39 ; s detergents and emulsifiers ( 1980 , allured publ . co ., ridgewood , n . j .) for examples of appropriate surface active agents . similarly , such formulations may be applied to the soil either as a liquid or a granule . for use as a preemergence herbicide the active compounds are typically applied at a rate of from about 0 . 01 to about 10 pounds per acre ( about 0 . 01 to about 11 kg / ha ) to soil which contains weed and crop seed . such application is made either to the surface of the soil or into the upper one to three inches ( 2 . 5 to 7 . 5 cm .) of soil . when employed as a postemergence herbicide , the compounds are typically applied at a rate of from about 0 . 01 to about 10 pounds per acre ( about 0 . 01 to about 11 kg / ha ) to the aerial portions of weeds . the most suitable rate of application in any given case may depend on such factors as soil type , soil ph , soil organic matter content , the quantity and intensity of rainfall before and after treatment , the air and soil temperature , light intensity and light duration per day . all of these factors can have an influence on the efficacy of the chemicals for a given weed control use . however , one skilled in the art can , by routine experimentation , readily determine optimum conditions for employment of any particular compound . it is particularly important in the practice of the present invention that the compounds be applied during the natural corn growing season , i . e ., conditions of sunlight intensity , day length and temperature typically found in the so - called &# 34 ; corn belt &# 34 ; states , for example iowa or illinois , during may or june . it has been found that when applied for postemergent use under artificial light in a controlled environment chamber , the present compounds generally do not exhibit selectivity and tend to cause substantial injury to corn crops . particularly good selectivity is present when the compounds are used under greenhouse conditions of natural sunlight of more than 11 - 12 hours per day , or in the field with natural sunlight of more than 10 - 11 hours per day . the herbicidal use may include control of vegetation at industrial sites or selective weed control in crop fields . the following examples are intended to further illustrate the invention and are not intended to limit the scope of the invention in any manner whatsoever . to a one liter three - necked flask equipped with mechanical stirrer , thermometer , and connecting tube were added 29 . 0929 grams ( 0 . 1462 mol ) of 2 , 6 - dichloroquinoxaline , 58 . 1404 grams ( 0 . 5280 mol ) of hydroquinone , and a solution of 28 . 3859 grams ( 0 . 5059 mol ) of potassium hydroxide in 400 milliliters of water . the mixture was heated at 88 ° c . for 2 . 5 hours , cooled to 40 ° c ., and 300 milliliters of water added . the slurry was filtered on a buchner funnel , and the solid washed with water until a clear filtrate was achieved the product was dried under vacuum for 20 hours , resulting in 36 . 5000 grams of 2 -( 4 - hydroxyphenoxy )- 6 - chloroquinoxaline , a 92 % yield . to a 100 milliliter roundbottom flask equipped with reflux condenser , connecting tube , stir bar , and nitrogen atmosphere were added 2 . 0000 grams ( 7 . 334 × 10 - 3 mol ) of 2 -( 4 - hydroxyphenoxy )- 6 - chloroquinoxaline , 0 . 8797 grams ( 7 . 3343 × 10 - 3 mol ) of bromoacetonitrile , 2 . 0272 grams ( 0 . 0147 mole ) of anhydrous potassium carbonate , and 40 milliliters of acetonitrile . the mixture was refluxed for 20 hours , filtered hot through a buchner funnel , and the acetonitrile removed by rotary evaporation . the combined residue of solvent removal and dichloromethane washings of potassium carbonate were plug filtered through a column of alumina with 150 milliliters of dichlormethane . removal of dichloromethane by rotary evaporation resulted in 1 . 8291 grams of white solid 2 -[ 4 -( 6 - chloro - 2 - quinoxalinyloxy ) phenoxy ] acetonitrile ( melting point 145 °- 146 . 5 ° c . ), an 80 % yield . nmr and ir spectra of the final products and intermediates , were consistent with theoretical values . the nmr spectrum ( cdc1 3 ) was as follows : 4 . 81 ( s , 2h ), 7 . 08 ( d , 2h ), 7 . 28 ( d , 2h ), 7 . 64 ( m , 2h ), 8 . 50 ( s , 1h ), 68 ( s , 1h ). ( note : s = singlet , d = doublet , t = triplet , q = quartet and m = multiplet .) 2 -[ 4 -( 6 - chloro - 2 - quinoxalinyloxy ) phenoxy ] propionitrile ( compound no . 2 ) was prepared essentially according to the scheme set forth in example 1 , except that 1 . 9695 grams of 2 - bromopropionitrile were substituted for the bromoacetonitrile . 3 . 6921 grams of product ( melting point 126 °- 128 ° c .) were obtained , a 77 % yield . the nmr spectrum ( cdc1hd 3 ) was as follows : 1 . 83 ( d , 3h ), 4 . 92 ( q , 1h ), 7 . 08 - 7 . 28 ( q , 4h ), 7 . 63 ( m , 2h ), 8 . 05 ( s , 1h ), 8 . 69 ( s , 1h ). to illustrate the effectiveness of the compounds 1 and 2 of this invention as preemergence herbicides , 300 mg of each compound were dissolved in 10 ml acetone to which 30 mg of an emulsifying agent , ethoxylated sorbitan monolaurate , were added . the solution was diluted to 100 ml with distilled water . ten milliliters of the 3000 ppm solution were diluted to 250 ppm with distilled water . the chemical was applied at the rate of 10 lb / a ( 11 . 2 kg / ha ) by drenching 46 ml of the 250 ppm solution on the surface of soil in 41 / 2inch ( 11 . 25 cm ) plastic pots wherein seeds of the following weeds had been planted : velvet leaf ( abutilon theoohrasti medic .) ( vl ), prickly sida ( sida soinosa l .) ( ps ), tall morningglory ( ioomea purourea l . roth ) ( tm ), switchgrass ( panicum viroatum l .) ( sg ), barnyard grass ( echinolchloa crus - oalli ( l .) beauv .) ( bg ), and green foxtail ( setaria viridis ) ( l .) beauv .) ( gf ). the percent control of the weeds compared to untreated checks was determined two weeks after treatment . the results of such testing are summarized in table i . the data presented indicates the good to excellent herbicidal efficacy exhibited by the compounds . table i______________________________________preemergence activity (% control at 11 . 2 kg / ha ) compound vl ps tm bg sg gf______________________________________1 0 0 0 100 50 902 0 0 0 50 100 25______________________________________ to test the effectiveness of compounds 1 and 2 of this invention as postemergence herbicides , a 3000 ppm solution of each compound ( produced in accordance with the process described under example 3 ) was atomized employing a devilbiss [ trademark ] sprayer , wetting the foliage to the drip point . the remainder of the procedure was the same as described under example 3 . the weeds , which were the same species as described under example 3 , were treated six days after emergence . the percent weed control was evaluated two weeks after treatment . the results of such testing are summarized in table ii . table ii______________________________________postemergence activity (% control at 3000 ppmcompound vl ps tm bg sg gf______________________________________1 0 0 0 100 100 92 95 75 55 65 35 95______________________________________ the above data demonstrate the desirable postemergent herbicidal control exhibited by compounds 1 and 2 . to illustrate the effectiveness of compound 1 of this invention as a corn - safe selective postemergence herbicide , the 3000 ppm solution prepared as described in example 3 was diluted with distilled water to 250 ppm and applied to foliage as described in example 3 . the commercial product hoelon 3ec ® ( hoechst ) was included as a standard . the foliage included weedy grasses described in example 3 in addition to the crops corn , soybeans and cotton . the foliage was planted in a connecticut greenhouse on may 16 , and was treated on may 26 . the percent weed control and crop injury was determined on jun . 12 . the results are set forth in table iii , and establish the desirable selectivity of compound 1 as it gives good control of several grass weeds but is substantially innocuous to corn at the dose rates tested . table iii______________________________________ percent weed control or crop injurycom - soy - pound sg bg gf corn bean cotton______________________________________1 100 100 90 0 0 0hoelon 100 100 60 100 0 03ec * ______________________________________ * 2 , 4 - dichlorophenoxyphenoxy acetic acid to further illustrate the effectiveness of compound 1 of this invention as a corn - safe selective postemergence herbicide , field tests were run in which five corn hybrids ( designated c9979 , c6114 , c8004 and c1914 by the independent professional seedsmans association , and pioneer 3295 ) along with two grass weeds ( giant foxtail , &# 34 ; gf &# 34 ;; and barnyard grass , &# 34 ; bg &# 34 ;) were planted in an illinois field on april 24 . the crops were treated with various amounts of compound 1 in early jun ., and the amount of crop control was evaluated 33 days after treatment compared to an untreated control . the active ingredient was formulated as follows : ______________________________________compound 1 ( 90 % active ) 11 . 25 % by weightsolvent ( exxon aromatic 150 ) 38 . 75 % by weightsolvent ( 1 - methyl - 2 - pyroll - 40 % by weightidinone ) emulsifier ( witco sponto n500b ) 10 % by weight______________________________________ that produces a formulation containing 10 % active ingredient by weight . the required amount of formulation to produce the indicated rate per acre is added to water , mixed with one quart of an adjuvant containing 83 % mineral oil and 17 % emulsifiers , then brought up to a total spray volume of 20 gallons per acre with water . the results are set forth in table iv , and establish the desirable selectivity of compound 1 as it gives good control of several grass weeds but is substantially innocuous to corn at the dose rates tested . table iv______________________________________rate percent weed control1b / a gf bg 3295 c9979 c6114 c8004 c1914______________________________________0 . 50 100 90 . 0 0 0 0 0 00 . 25 100 43 . 3 0 0 0 0 0 0 . 125 99 . 3 30 . 0 0 0 0 0 0______________________________________ to illustrate the effectiveness of compound 2 of this invention as a corn - safe selective postemergence herbicide , various concentrations of the compound were prepared and applied as in example 5 to the following weeds and crops : velvet leaf ( abutilon theoohrasti medic .) ( vl ), prickly sida ( sida spinosa l .) ( ps ), wild morningglory ( ipomopa sp .) ( wm ), barnyard grass ( echinolchloa crus - galli ( l .) beauv .) ( bg ), green foxtail ( setaria viridis ) ( l .) beauv .) ( gf ), wild oat ( avena fatua l .) ( wo ), corn ( cr ), soybean ( so ), cotton ( ct ) and rice ( rc ). the weeds and crops were planted in mid - september in a connecticut greenhouse and were treated eight days later . the percent weed control and crop injury was determined 2 weeks after treatment . the results are set forth in table iv , and establish the desirable selectivity of compound 2 as it gives good control of several grass weeds but is substantially innocuous to corn at the dose rates tested . table v______________________________________rate percent weed controlppm vl ps wm wo gf bg cr so ct rc______________________________________3000 90 0 20 10 100 95 0 20 20 502000 90 0 10 0 100 85 0 20 20 501000 90 0 10 0 100 85 0 20 20 50______________________________________
herbicidal methods utilizing compounds having the structure ## str1 ## wherein : n is 0 , 1 , 2 , or 3 ; r is h or alkyl ; and r 1 is halogen , nitro , methyl , halomethyl , methoxy , halomethoxy or ethoxy are disclosed which control the growth of undesirable weeds but are substantially innocuous to corn . herbicidal compositions comprising the compounds and a carrier are also disclosed .