Acifluorfen is the

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

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 con ...

for an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

used as an

herbicide Herbicides (, ), also commonly known as weed killers, 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 f ...

. 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 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 allows plants to absorb energy ...

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 organi ...

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. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

s naturally have a high tolerance to acifluorfen and its

salts In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions (anions), which results in a compound with no net electric charge (electrically neutral). ...

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

broadleaf weed Broadleaf weeds are dicotyledonous weeds that may grow in lawns, gardens or yards. They can be easy to spot when growing among grasses. They are tougher than grassy monocot weeds, multiply with ease, and can be very hard to eradicate. Basic charact ...

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, invented by

Rohm & Haas Rohm and Haas Company is a US manufacturer of specialty chemicals for end use markets such as building and construction, electronic devices, packaging, household and personal care products. Headquartered in Philadelphia, the company is organize ...

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, also known as a chemical analog or simply an analog, is a chemical compound, compound having a chemical structure, structure similar to that of another compound, but differing from it in respect to a certain component. It can ...

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 goods or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create and ...

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 reaction ...

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 an aqueous solution of hydrogen bromide. It 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 ...

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 compone ...

as solvent. : Acifluorfen synthesis

Mechanism of action

The detailed mechanism of action for nitrofen, acifluorfen and related diphenyl ether herbicides such as fomesafen 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. The ...

: 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 are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms; sometimes they abstract an electron from the substrate, and sometimes they abstract a hydro ...

which activates oxygen, leading to

lipid peroxidation Lipid peroxidation, or lipid oxidation, is a complex chemical process that leads to oxidative degradation of lipids, resulting in the formation of peroxide and hydroperoxide derivatives.{{Cite journal , last1=Ayala , first1=Antonio , last2=Muñoz ...

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

Usage

In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, the

Environmental Protection Agency Environmental Protection Agency may refer to the following government organizations: * Environmental Protection Agency (Queensland), Australia * Environmental Protection Agency (Ghana) * Environmental Protection Agency (Ireland) * Environmenta ...

(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 ...

(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,'' also known as velvetleaf, velvet plant, velvetweed and the Chinese jute is an annual plant in the Family (biology), family Malvaceae that is native to South Asia, southern Asia and it serves as a type species of the genu ...

'', '' Acalypha ostryifolia'', ''

Acanthospermum hispidum ''Acanthospermum hispidum'' (bristly starbur, goat's head, hispid starburr, starbur) is an annual plant in the family Asteraceae, which is native to Central and South America. This plant is cited as a weed in cotton culture in Brazil, and it is ...

'', ''

Amaranthus palmeri ''Amaranthus palmeri'' is a species of edible flowering plant in the amaranth genus. It has several common names, including carelessweed, dioecious amaranth, Palmer's amaranth, Palmer amaranth, and Palmer's pigweed. It is native to most of the s ...

'', ''

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 lea ...

'', ''

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 winter rocket, rocketcress, yellow rocketcress, yellow rocket, wound rocket, herb barbara, creases, or creasy greens, is a Biennial plant, biennial herb of the ...

'', '' 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. The species was first classified by Carl Linnaeus in 1753. The specific epithet ''Sativum, sativa'' means 'cultivated'. Indigenous to East Asia, Eastern Asia, the pla ...

'', ''

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, South Asia and North America that is often found ...

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

Chenopodium album ''Chenopodium album'' is a fast-growing annual plant in the flowering plant family Amaranthaceae. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb's quarters, melde, goosefoot, wild spinach a ...

'', ''

Citrullus lanatus The watermelon (''Citrullus lanatus'') is a species of flowering plant in the family Cucurbitaceae, that has a large, edible fruit. It is a scrambling and trailing vine-like plant, and is widely cultivated worldwide, with more than 1,000 ...

'', ''

Convolvulus arvensis ''Convolvulus arvensis'', or field bindweed, is a species of bindweed in the Convolvulaceae native to Europe and Asia. It is a rhizomatous and climbing or creeping herbaceous perennial plant with stems growing to in length. It is usually found a ...

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

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

'', ''

Datura stramonium ''Datura stramonium'', known by the common names thornapple, jimsonweed (jimson weed), or devil's trumpet, is a poisonous flowering plant in the ''Datureae, Daturae'' Tribe (botany), tribe of the nightshade family Solanaceae. Its likely origi ...

'', ''

Digitaria ''Digitaria'' is a genus of plants in the 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. They ar ...

'', ''

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, commo ...

'', ''

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 lati ...

'', ''

Euphorbia heterophylla ''Euphorbia heterophylla'', also known under the common names of Mexican fireplant, painted euphorbia, Japanese poinsettia, paintedleaf, painted spurge and milkweed, is a plant belonging to the Euphorbiaceae or spurge family. Distribution ''Euph ...

'', ''

Helianthus annuus The common sunflower (''Helianthus annuus'') is a species of large annual forb of the daisy family Asteraceae. The common sunflower is harvested for its edible oily seeds, which are often eaten as a snack food. They are also used in the pro ...

'', ''

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

'', '' Ipomoea quamoclit'', ''

Melochia corchorifolia ''Melochia corchorifolia'', the chocolateweed, is a weedy tropical plant that is typically seen in the wastelands. It has been most frequently observed to grow in open areas, such as highways.Mohlenbrock, R. (1982) The Illustrated Flora of Illino ...

'', '' Mollugo verticillata'', '' Polygonum convolvulus'', ''

Portulaca oleracea ''Portulaca oleracea'' (common purslane, also known as little hogweed, or pursley) is a succulent plant in the family Portulacaceae. Description The plant may reach in height. It has smooth, reddish, mostly prostrate stems, and the leaves, w ...

'', '' Richardia scabra'', '' Sesbania exaltata'', '' Setaria faberi'', ''

Solanum rostratum ''Solanum rostratum'' is a species of nightshade (genus ''Solanum'') that is native to the United States and northern and central Mexico. Common names include buffalobur nightshade, buffalo-bur, spiny nightshade, Colorado bur, Kansas thistle, ba ...

'', ''

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, Noogoora burr, 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 ...

''. 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 approximately were applied — mainly in soybean. The compound is not registered for use in the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

, 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 wate ...

.The Proposition 65 List
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References

{{commons category PPO herbicides Benzoic acids Nitrobenzene derivatives Chloroarenes Trifluoromethyl compounds Group 14 herbicides

History

Synthesis

Mechanism of action

Usage

Safety

See also

References