Acifluorfen is the

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

for an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

used as an

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

. It acts by inhibiting the enzyme

protoporphyrinogen oxidase Protoporphyrinogen oxidase or protox is an enzyme that in humans is encoded by the ''PPOX'' gene. Protoporphyrinogen oxidase is responsible for the seventh step in biosynthesis of protoporphyrin IX. This porphyrin is the precursor to hemoglobin, ...

which is necessary for

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

synthesis Synthesis or synthesize may refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors ** Organic synthesis, the chemical synthesis of organ ...

Soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...

s naturally have a high tolerance to acifluorfen and its

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...

, via metabolic disposal by glutathione ''S''-transferase. It is effective against

broadleaf weed Broadleaf weeds are unwanted tough plants that may grow in lawns, gardens or yards. They can be easy to spot when growing among grasses. They multiply with ease and can be very hard to eradicate. Basic characteristics Dicotyledon, Broadleaf Weed, w ...

s and grasses and is used agriculturally on fields growing soybeans, peanuts, peas, and rice.

History

The nitrophenyl ethers are a well-known class of herbicides, the oldest member of which was

nitrofen Nitrofen is an herbicide of the diphenyl ether class. Because of concerns about its carcinogenicity, the use of nitrofen has been banned in the European Union and in the United States since 1996. It has been superseded by related protoporphyrino ...

, invented by Rohm & Haas and first registered for sale in 1964. This area of chemistry became very competitive, with the Mobil Oil Corporation's filing in 1969 and grant in 1974 of a patent to the

structural analog A structural analog (analogue in modern traditional English; Commonwealth English), also known as a chemical analog or simply an analog, is a compound having a structure similar to that of another compound, but differing from it in respect to a ce ...

with a COOCH₃ group adjacent to the nitro group of nitrofen. This product, bifenox, was launched with the

brand name A brand is a name, term, design, symbol or any other feature that distinguishes one seller's good or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create an ...

Mowdown in 1981. Meanwhile Rohm & Haas introduced acifluorfen (as its sodium salt with brand name Blazer) in 1980, having developed it under the code number RH-6201. It had much improved properties including a wider spectrum of herbicidal effect and good safety to soybean crops. The first patent for the material was published in December 1975, although an earlier Belgian patent published in September 1973 had described related chemistry.

Synthesis

The preparation of acifluorfen first described in the Rohm & Haas patent includes as its final steps an

Ullmann condensation The Ullmann condensation or Ullmann-type reaction is the copper-promoted conversion of aryl halides to aryl ethers, aryl thioethers, aryl nitriles, and aryl amines. These reactions are examples of cross-coupling reactions. Ullmann-type reactions ...

between 2-chloro-4-trifluoromethylphenol and 2-nitro-5-fluorobenzonitrile. The intermediate is then

hydrolysed Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

using

hydrobromic acid Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains 47.6% HBr by mass, which is 8.77 mol/L. H ...

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...

as solvent. : Acifluorfen synthesis

Mechanism of action

The detailed mechanism of action for

, acifluorfen and related diphenyl ether herbicides such as

fomesafen Fomesafen is the ISO common name for an organic compound used as an herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase which is necessary for chlorophyll synthesis. Soybeans naturally have a high tolerance to fomesafen, via ...

was unknown at the time they were invented. The effects visible on whole plants are

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

and

desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

: several hypotheses were advanced regarding the molecular-level interactions which might explain these symptoms. The now-accepted explanation for the damage is that these compounds inhibit the enzyme

, which leads to an accumulation of

protoporphyrin IX Protoporphyrin IX is an organic compound, classified as a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like heme (hemoglobin) and chlorophyll. It is a deeply colored solid that is not sol ...

in the plant cells. This is a potent

photosensitizer Photosensitizers produce a physicochemical change in a neighboring molecule by either donating an electron to the substrate or by abstracting a hydrogen atom from the substrate. At the end of this process, the photosensitizer eventually returns to ...

which activates oxygen, leading to

lipid peroxidation Lipid peroxidation is the chain of reactions of oxidative degradation of lipids. It is the process in which radical (chemistry), free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by ...

. Both light and oxygen are required for this process to kill the plant.

Usage

In the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, the

Environmental Protection Agency A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...

(EPA) is responsible for regulating pesticides under the

Federal Insecticide, Fungicide, and Rodenticide Act The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) is a United States federal law that set up the basic U.S. system of pesticide regulation to protect applicators, consumers, and the environment. It is administered and regulated by t ...

(FIFRA), the

Food Quality Protection Act The Food Quality Protection Act (FQPA), or H.R.1627, was passed unanimously by Congress in 1996 and was signed into law by President Bill Clinton on August 3, 1996. The FQPA standardized the way the Environmental Protection Agency (EPA) would man ...

(FQPA) and the Pesticide Registration Improvement Act (PRIA). A pesticide can only be used legally according to the directions on the label that is included at the time of the sale of the pesticide. The purpose of the label is "to provide clear directions for effective product performance while minimizing risks to human health and the environment". A label is a legally binding document that mandates how the pesticide can and must be used and failure to follow the label as written when using the pesticide is a federal offence. Acifluorfen sodium is normally applied postemergence (when weeds are visible in the crop). It controls or suppresses broadleaf weeds, grasses and sedges and is effective on a very wide range of species including ''

Abutilon theophrasti ''Abutilon theophrasti'' (velvetleaf, velvet plant, velvetweed, Chinese jute, China jute, crown weed, buttonweed, lantern mallow, butterprint, pie-marker, or Indian mallow) is an annual plant in the family Malvaceae, native to southern Asia. It' ...

'', '' Acalypha ostryifolia'', '' Acanthospermum hispidum'', '' Amaranthus palmeri'', ''

Ambrosia artemisiifolia ''Ambrosia artemisiifolia'', with the common names common ragweed, annual ragweed, and low ragweed, is a species of the genus '' Ambrosia'' native to regions of the Americas. Taxonomy The species name, ''artemisiifolia'', is given because the le ...

'', ''

Anoda cristata ''Anoda cristata'' is a species of flowering plant in the Malvaceae, mallow family known by many common names, including spurred anoda, crested anoda, and violettas. It is native to North and South America. It is known throughout the rest of th ...

'', ''

Barbarea vulgaris ''Barbarea vulgaris'', also called wintercress (usual common name), or alternatively herb barbara, rocketcress, yellow rocketcress, winter rocket, yellow rocket, and wound rocket, is a biennial herb of the genus ''Barbarea'', belonging to the fam ...

'', '' Brassica kaber'', ''

Calystegia sepium ''Calystegia sepium'' (hedge bindweed, Rutland beauty, bugle vine, heavenly trumpets, bellbind, granny-pop-out-of-bed and many others) is a species of flowering plant in the family Convolvulaceae. It has a cosmopolitan distribution, subcosmopolit ...

'', ''

Cannabis sativa ''Cannabis sativa'' is an annual Herbaceous plant, herbaceous flowering plant indigenous to East Asia, Eastern Asia, but now of cosmopolitan distribution due to widespread cultivation. It has been cultivated throughout recorded history, used as ...

'', ''

Cardiospermum halicacabum ''Cardiospermum halicacabum'', known as the lesser balloon vine, balloon plant or love in a puff, is a climbing plant widely distributed across tropical and subtropical areas of Africa, Australia, and North America that is often found as a weed a ...

'', '' Cassia obtusifolia'', ''

Chenopodium album ''Chenopodium album'' is a fast-growing weedy annual plant in the genus ''Chenopodium''. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb's quarters, melde, goosefoot, wild spinach and fat-h ...

'', ''

Citrullus lanatus Watermelon (''Citrullus lanatus'') is a flowering plant species of the Cucurbitaceae family and the name of its edible fruit. A scrambling and trailing vine-like plant, it is a highly cultivated fruit worldwide, with more than 1,000 varieti ...

'', ''

Convolvulus arvensis ''Convolvulus arvensis'', the field bindweed, is a species of bindweed that is rhizomatous and is in the morning glory family (Convolvulaceae), native to Europe and Asia. It is a climbing or creeping herbaceous perennial plant with stems growing ...

'', '' Croton glandulosus'', ''

Cyperus esculentus ''Cyperus esculentus'' (also called chufa, tiger nut, atadwe, yellow nutsedge, and earth almond) is a species of plant in the Cyperaceae, sedge family widespread across much of the world. It is found in most of the Eastern Hemisphere, including S ...

'', ''

Datura stramonium ''Datura stramonium'', known by the common names thorn apple, jimsonweed (jimson weed), devil's snare, or devil's trumpet, is a poisonous flowering plant of the nightshade family Solanaceae. It is a species belonging to the ''Datura'' genus a ...

'', ''

Digitaria ''Digitaria'' is a genus of plants in the Poaceae, grass family native to tropical and warm temperate regions but can occur in tropical, subtropical, and cooler temperate regions as well. Common names include crabgrass, finger-grass, and fonio. ...

'', ''

Echinochloa crus-galli ''Echinochloa crus-galli'' is a type of wild grass originating from tropical Asia that was formerly classified as a type of panicum grass. It is commonly known as cockspur (or cockspur grass), barnyard millet, Japanese millet, water grass, common ...

'', ''

Eleusine indica ''Eleusine indica'', the Indian goosegrass, yard-grass, goosegrass, wiregrass, or crowfootgrass, is a species of grass in the family Poaceae. It is a small annual grass distributed throughout the warmer areas of the world to about 50 degrees lat ...

'', '' Euphorbia heterophylla'', ''

Helianthus annuus The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), as b ...

'', ''

Hibiscus trionum ''Hibiscus trionum'', commonly called flower-of-an-hour, bladder hibiscus, bladder ketmia, bladder weed, modesty, puarangi, shoofly, and venice mallow, is an annual plant native to the Old World tropics and subtropics. It has spread throughout s ...

'', ''

Ipomoea quamoclit ''Ipomoea quamoclit'', commonly known as cypress vine, cypress vine morning glory, cardinal creeper, cardinal vine, star glory, star of Bethlehem or hummingbird vine, is a species of vine in the family Convolvulaceae native to tropical regions o ...

'', '' Melochia corchorifolia'', ''

Mollugo verticillata ''Mollugo verticillata'', the green carpetweed (also known as Indian chickweed), is a rapidly spreading annual plant from tropical Americas, America. In eastern North America, it is a common weed growing in disturbed areas. It forms a prostrate ...

'', '' Polygonum convolvulus'', ''

Portulaca oleracea ''Portulaca oleracea'' (common purslane, also known as little hogweed, or pursley) is an annual (actually tropical perennial in USDA growing zones 10–11) succulent in the family Portulacaceae. Description The plant may reach in height. It ...

'', '' Richardia scabra'', '' Sesbania exaltata'', ''

Setaria faberi ''Setaria faberi'', the Japanese bristlegrass, nodding bristle-grass, Chinese foxtail, Chinese millet, giant bristlegrass, giant foxtail or nodding foxtail, is an Asian grass. It is a summer annual, with plants emerging from seeds in the spring, ...

'', '' Solanum rostratum'', ''

Sorghum halepense Johnson grass or Johnsongrass, ''Sorghum halepense'', is a plant in the grass family, Poaceae, native to Asia and northern Africa. The plant has been introduced to all continents except Antarctica, and most larger islands and archipelagos. It re ...

'', ''

Striga asiatica ''Striga asiatica'', the Asiatic witchweed or the red witchweed, is a hemiparasitic plant in the family Orobanchaceae. It is native to Asia and sub-Saharan Africa, but has been introduced into other parts of the world including Australia and th ...

'' and ''

Xanthium strumarium ''Xanthium strumarium'' (rough cocklebur, clotbur, common cocklebur, large cocklebur, woolgarie bur) is a species of annual plants of the family Asteraceae. Some sources claim it originates in southern Europe and Asia, but has been extensively na ...

''. The product is typically used at application rates of 0.375 lb a.i. per acre. The estimated annual use of acifluorfen in US agriculture is mapped by the US Geological Service and shows that in 2017, the latest date for which figures are available, approximately were applied — mainly in soybean. The compound is not registered for use in the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...

, although a closely related nitrophenyl ether, bifenox, is available there.

Safety

In California, acifluorfen is listed as "known to the state to cause cancer or reproductive toxicity" according to

Proposition 65 Proposition 65 (formally titled The Safe Drinking Water and Toxic Enforcement Act of 1986, and also referred to as Prop 65) is a California law passed by direct voter initiative in 1986 by a 63%–37% vote. Its goals are to protect drinking water s ...

.The Proposition 65 List
/ref>

References

{{commons category, Acifluorfen PPO herbicides Benzoic acids Nitro compounds Chloroarenes Trifluoromethyl compounds

History

Synthesis

Mechanism of action

Usage

Safety

See also

References