Bifenox 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 ...

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 It has been superseded by related protoporphyrino ...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. 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 had patented and developed

acifluorfen Acifluorfen 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 acifluorfen ...

(as its sodium salt with brand name Blazer) in 1980. Both compounds had much improved properties including a wider spectrum of herbicidal effect and good safety to some crops, including

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 ...

Synthesis

The preparation of bifenox first described in the Mobil patent includes as its final step 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 the potassium salt of 2,4-dichlorophenol and methyl 2-nitro-5-chlorobenzoic acid.

Mechanism of action

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

Uses

Bifenox is not currently used in the United States although in 1981 it had been subject to a full regulatory review, under the then-new "Registration Standard" process. Within the European Union, a 2-tiered approach is used for the approval and authorisation of pesticides. Firstly, before a formulated product can be developed for market, the active substance must be approved for the European Union. After this has been achieved, authorisation for the specific product must be sought from every Member State that the applicant wants to sell it to. Afterwards, there is a monitoring programme to make sure the pesticide residues in food are below the limits set by the

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

. Bifenox is registered for use against weeds in crops including cereals, soybeans, sugarbeet and rice. In Switzerland, some of its

formulations Formulation is a term used in various senses in various applications, both the material and the abstract or formal. Its fundamental meaning is the putting together of components in appropriate relationships or structures, according to a formul ...

can be used in lawns and orchards. Bifenox is normally applied postemergence (when weeds are visible in the crop). It controls or suppresses a wide range of species including ''

Capsella bursa-pastoris ''Capsella bursa-pastoris'', known as shepherd's purse because of its triangular flat fruits, which are purse-like, is a small annual and ruderal flowering plant in the mustard family (Brassicaceae). It is native to eastern Europe and Asia minor, ...

'', ''

Galium aparine ''Galium aparine'', with common names including cleavers, clivers, catchweed and sticky willy among others, is an annual, herbaceous plant of the family Rubiaceae. Names ''Galium aparine'' is known by a variety of common names in English. They ...

'', ''

Lamium purpureum ''Lamium purpureum'', known as red dead-nettle, purple dead-nettle, or purple archangel, is an annual herbaceous flowering plant native to Europe and Asia. Varieties: * ''Lamium purpureum'' var. ''hybridum'' (Vill.) Vill. (synonym: ''Lamium hybr ...

'', ''

Myosotis arvensis ''Myosotis arvensis'' or field forget-me-not is a herbaceous annual to short lived perennial flowering plant in the family Boraginaceae. Clive Stace describes this plant as having the following characteristics: * Upright, to ; softly hairy, wi ...

'', ''

Papaver rhoeas ''Papaver rhoeas'', with common names including common poppy, corn poppy, corn rose, field poppy, Flanders poppy, and red poppy, is an annual herbaceous species of flowering plant in the poppy family Papaveraceae. It is a temperate native with ...

'', '' Veronica hederifolia'', ''

Veronica persica ''Veronica persica'' is a flowering plant in the family Plantaginaceae. Common names include birdeye speedwell, common field-speedwell, Persian speedwell, large field speedwell, bird's-eye, or winter speedwell. It is native to Eurasia and is wide ...

'' and ''

Viola arvensis left, flower and leaves ''Viola arvensis'' is a species of violet known by the common name field pansy. It is native to Europe, western Asia, and North Africa, and it is known on other continents as an introduced species and a weed A weed i ...

''. The product is typically used at application rates of 720 g a.i. per hectare.

References

External links

* {{commons category, Bifenox PPO herbicides Nitro compounds Methyl esters Chlorobenzenes