Misplaced Pages

#336663

63-633: O -Ethyl methylphosphonothioic acid (EMPTA) is an organophosphate compound . A dual-use chemical, it has constructive uses in the synthesis of pesticides and pharmaceuticals, and it is also a precursor in the synthesis of nerve agents such as Agent VM and Agent VX . The detection of EMPTA is cited as a major influence in the United States' 1998 decision to destroy the Al-Shifa pharmaceutical factory in Sudan. This article about an organic compound

126-401: A carboxylic acid is an organic acid that contains a carboxyl group ( −C(=O)−OH ) attached to an R-group . The general formula of a carboxylic acid is often written as R−COOH or R−CO 2 H , sometimes as R−C(O)OH with R referring to an organyl group (e.g., alkyl , alkenyl , aryl ), or hydrogen , or other groups. Carboxylic acids occur widely. Important examples include

189-407: A of acetic acid is 4.76 whereas trifluoroacetic acid, with a trifluoromethyl substituent , has a p K a of 0.23). Electron-donating substituents give weaker acids (the p K a of formic acid is 3.75 whereas acetic acid, with a methyl substituent , has a p K a of 4.76) Deprotonation of carboxylic acids gives carboxylate anions; these are resonance stabilized , because the negative charge

252-437: A base and deprotonates the acid. A second equivalent will attack the carbonyl group to create a geminal alkoxide dianion, which is protonated upon workup to give the hydrate of a ketone. Because most ketone hydrates are unstable relative to their corresponding ketones, the equilibrium between the two is shifted heavily in favor of the ketone. For example, the equilibrium constant for the formation of acetone hydrate from acetone

315-428: A carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents , such as 3-chloropropanoic acid . Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another parent structure, such as 2-carboxyfuran . The carboxylate anion ( R−COO or R−CO − 2 ) of a carboxylic acid is usually named with the suffix -ate , in keeping with

378-426: A chlorine atom using thionyl chloride to give acyl chlorides . In nature, carboxylic acids are converted to thioesters . Thionyl chloride can be used to convert carboxylic acids to their corresponding acyl chlorides. First, carboxylic acid 1 attacks thionyl chloride, and chloride ion leaves. The resulting oxonium ion 2 is activated towards nucleophilic attack and has a good leaving group, setting it apart from

441-456: A high salt tolerance allows co-spraying of pesticides and inorganic fertilisers. Low-levels of phosphate mono-esters, such as potassium cetyl phosphate , find use in cosmetic creams and lotions. These in oil-in-water formulations are primarily based on non-ionic surfactants, with the anionic phosphate acting as emulsion-stabilisers. Phosphate tri-esters such as tributyl phosphate are used as anti-foaming agent in paints and concrete. Although

504-873: A large scale. They are also frequently found in nature. Esters of fatty acids are the main components of lipids and polyamides of aminocarboxylic acids are the main components of proteins . Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (component of vinegar, precursor to solvents and coatings), acrylic and methacrylic acids (precursors to polymers, adhesives), adipic acid (polymers), citric acid (a flavor and preservative in food and beverages), ethylenediaminetetraacetic acid (chelating agent), fatty acids (coatings), maleic acid (polymers), propionic acid (food preservative), terephthalic acid (polymers). Important carboxylate salts are soaps. In general, industrial routes to carboxylic acids differ from those used on

567-531: A low solubility in water (0.2 g/L), but its sodium salt is very soluble in water. Carboxylic acids tend to have higher boiling points than water, because of their greater surface areas and their tendency to form stabilized dimers through hydrogen bonds . For boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be vaporized, increasing the enthalpy of vaporization requirements significantly. Carboxylic acids are Brønsted–Lowry acids because they are proton (H ) donors. They are

630-422: A matter of prolonged debate; the phosphorus atom is classically hypervalent , as it possesses more bonds than the octet rule should allow. The focus of debate is usually on the nature of the phosphoryl P=O bond, which displays (in spite of the common depiction) non-classical bonding, with a bond order somewhere between 1 and 2. Early papers explained the hypervalence in terms of d- orbital hybridisation , with

693-523: A normal carboxylic acid. In the next step, 2 is attacked by chloride ion to give tetrahedral intermediate 3 , a chlorosulfite. The tetrahedral intermediate collapses with the loss of sulfur dioxide and chloride ion, giving protonated acyl chloride 4 . Chloride ion can remove the proton on the carbonyl group, giving the acyl chloride 5 with a loss of HCl . [REDACTED] Phosphorus(III) chloride (PCl 3 ) and phosphorus(V) chloride (PCl 5 ) will also convert carboxylic acids to acid chlorides, by

SECTION 10

#1732802042337

756-455: A practical one, as many cellular processes involve the mono- di and tri- phosphates of the same compound. For instance, the phosphates of adenosine ( AMP , ADP , ATP ) play a key role in many metabolic processes. [REDACTED] Phosphorus oxychloride reacts readily with alcohols to give organophosphates. This is the dominant industrial route and is responsible for almost all organophosphate production. When aliphatic alcohols are used

819-483: A sharp band associated with vibration of the C=O carbonyl bond ( ν C=O ) between 1680 and 1725 cm . A characteristic ν O–H band appears as a broad peak in the 2500 to 3000 cm region. By H NMR spectrometry, the hydroxyl hydrogen appears in the 10–13 ppm region, although it is often either broadened or not observed owing to exchange with traces of water. Many carboxylic acids are produced industrially on

882-474: A similar mechanism. One equivalent of PCl 3 can react with three equivalents of acid, producing one equivalent of H 3 PO 3 , or phosphorus acid , in addition to the desired acid chloride. PCl 5 reacts with carboxylic acids in a 1:1 ratio, and produces phosphorus(V) oxychloride (POCl 3 ) and hydrogen chloride (HCl) as byproducts. Carboxylic acids react with Grignard reagents and organolithiums to form ketones. The first equivalent of nucleophile acts as

945-406: A smaller scale because they require specialized equipment. Preparative methods for small scale reactions for research or for production of fine chemicals often employ expensive consumable reagents. Many reactions produce carboxylic acids but are used only in specific cases or are mainly of academic interest. Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of

1008-418: A softer more easily deformable material. In this way brittle polymers can be made more durable. The most frequently plasticised polymers are the vinyls ( PVC , PVB , PVA and PVCA ), as well as cellulose plastics ( cellulose acetate , nitrocellulose and cellulose acetate butyrate ). PVC dominates the market, consuming 80-90% of global plasticiser production. PVC can accept large amounts of plasticiser; it

1071-681: Is a stub . You can help Misplaced Pages by expanding it . Organophosphate compound Like most functional groups , organophosphates occur in a diverse range of forms, with important examples including key biomolecules such as DNA , RNA and ATP , as well as many insecticides , herbicides , nerve agents and flame retardants . OPEs have been widely used in various products as flame retardants, plasticizers , and performance additives to engine oil. The low cost of production and compatibility to diverse polymers made OPEs to be widely used in industry including textile, furniture, electronics as plasticizers and flame retardants. These compounds are added to

1134-511: Is a highly chemoselective agent for carboxylic acid reduction. It selectively activates the carboxylic acid to give the carboxymethyleneammonium salt, which can be reduced by a mild reductant like lithium tris( t -butoxy)aluminum hydride to afford an aldehyde in a one pot procedure. This procedure is known to tolerate reactive carbonyl functionalities such as ketone as well as moderately reactive ester, olefin, nitrile, and halide moieties. The hydroxyl group on carboxylic acids may be replaced with

1197-916: Is an important factor in biological, industrial and environmental settings. The wide variety of substitutes used in organophosphate esters results in great variations in physical properties. OPEs exhibit a wide range of octanol/water partition coefficients where log Kow values range from -0.98 up to 10.6. Mono- and di- esters are usually water soluble, particularity biomolecules. Tri-esters such as flame retardants and plasticisers have positive log Kow values ranging between 1.44 and 9.49, signifying hydrophobicity . Hydrophobic OPEs are more likely to be bioaccumulated and biomagnified in aquatic ecosystems. Halogenated organophosphates tend to be denser than water and sink, causing them to accumulate in sediments. Organophosphates are best known for their use as pesticides. The vast majority are insecticides and are used either to protect crops, or as vector control agents to reduce

1260-537: Is an important part of biochemistry and living systems achieve this using a variety of enzymes . Phosphorylation is essential to the processes of both anaerobic and aerobic respiration , which involve the production of adenosine triphosphate (ATP), the "high-energy" exchange medium in the cell. Protein phosphorylation is the most abundant post-translational modification in eukaryotes. Many enzymes and receptors are switched "on" or "off" by phosphorylation and dephosphorylation. The bonding in organophosphates has been

1323-404: Is associated with a number of heath risks, including organophosphate-induced delayed neuropathy (muscle weakness) and developmental neurotoxicity . There is limited evidence that certain compounds cause cancer, including malathion and diazinon . Children and farmworkers are considered to be at greater risk. Pesticide regulation in the United States and the regulation of pesticides in

SECTION 20

#1732802042337

1386-1043: Is common for products to be 0-50% plasticiser by mass, but loadings can be as high as 70-80% in the case of plastisols . Pure PVC is more than 60% chlorine by mass and is difficult to burn, but its flammability increases the more it is plasticised. Organophosphates find use because they are multifunctional; primarily plasticising but also imparting flame resistance. Compounds are typically triaryl or alkyl diaryl phosphates, with cresyl diphenyl phosphate and 2-ethylhexyl diphenyl phosphate being important examples respectively. These are both liquids with high boiling points. Organophosphates are more expensive than traditional plasticisers and so tend be used in combination with other plasticisers and flame retardants. Similar to their use as plastisiers, organophosphates are well suited to use as hydraulic fluids due to their low freezing points and high boiling points, fire-resistance, non-corrosiveness, excellent boundary lubrication properties and good general chemical stability. The triaryl phosphates are

1449-533: Is delocalized over the two oxygen atoms, increasing the stability of the anion. Each of the carbon–oxygen bonds in the carboxylate anion has a partial double-bond character. The carbonyl carbon's partial positive charge is also weakened by the - / 2 negative charges on the 2 oxygen atoms. Carboxylic acids often have strong sour odours. Esters of carboxylic acids tend to have fruity, pleasant odours, and many are used in perfume . Carboxylic acids are readily identified as such by infrared spectroscopy . They exhibit

1512-554: Is largely limited to certain niche areas. Compared to the more common sulfur-based anionic surfactants (such as LAS or SLES ), phosphate ester surfactants are more expensive and generate less foam. Benefits include high stability at extremes of pH, low skin irritation and a high tolerance to dissolved salts. In agricultural settings monoesters of fatty alcohol ethoxylates are used, which are able to disperse poorly miscible or insoluble pesticides into water. As they are low-foaming these mixtures can be sprayed effectively onto fields, while

1575-521: Is not a common industrial route, however large quantities of organophosphites are manufactured as antioxidant stabilisers for plastics. The gradual oxidation these generates organophosphates in the human environment. A more specialised alternative is the Atherton-Todd reaction, which converts a dialkyl phosphite to a phosphoryl chloride. This can then react with an alcohol to give an organophosphate and HCl. The formation of organophosphates

1638-496: Is only useful for forming methyl esters. Like esters , most carboxylic acids can be reduced to alcohols by hydrogenation , or using hydride transferring agents such as lithium aluminium hydride . Strong alkyl transferring agents, such as organolithium compounds but not Grignard reagents , will reduce carboxylic acids to ketones along with transfer of the alkyl group. The Vilsmaier reagent ( N , N -Dimethyl(chloromethylene)ammonium chloride; [ClHC=N (CH 3 ) 2 ]Cl )

1701-606: Is perhaps the most important. They are used in polyurethane (insulation, soft furnishings), PVC (wire and cable) phenolic resins and epoxy resins (varnishes, coatings and adhesives). The most important of the diphosphates is bisphenol-A bis(diphenyl phosphate) , with related analogues based around resorcinol and hydroquinone . These are used in polymer blends of engineering plastics , such as PPO / HIPS and PC / ABS , which are commonly used to make casing for electrical items like TVs, computers and home appliances. Organophosphates act multifunctionally to retard fire in both

1764-439: Is the low cost of phosphoric acid compared to phosphorus oxychloride. P 2 O 5 is the anhydride of phosphoric acid and acts similarly. The reaction yields equimolar amounts of di- and monoesters with no phosphoric acid. The process is mostly limited to primary alcohols, as secondary alcohols are prone to undesirable side reactions such as dehydration. Organophosphites can be easily oxidised to give organophosphates. This

1827-635: Is typically between 1-2, while the second OH deprotonates at a pKa between 6-7. As such, phosphate mono- and di-esters are negatively charged at physiological pH . This is of great practical importance, as it makes these compounds far more resistant to degradation by hydrolysis or other forms of nucleophilic attack, due to electrostatic repulsion between negative charges. This effects nearly all organophosphate biomolecules, such as DNA and RNA and accounts in-part for their high stability. The presence of this negative charge also makes these compounds much more water soluble. The water solubility of organophosphates

1890-542: Is under significant scrutiny as potential endocrine-disrupting chemical . Although their names imply that they are a single chemical, some (but not all) are produced as complex mixtures. For instance, commercial grade TCPP can contain 7 different isomers , while tricresyl phosphate can contain up to 10. This makes their safety profiles harder to ascertain, as material from different producers can have different compositions. Plasticisers are added to polymers and plastics to improve their flexibility and processability, giving

1953-905: The Novichok agents . Some of these can be considered organophosphates (in a broad sense), being derivatives of fluorophosphoric acid . Examples include A-232 , A-234 , A-262 , C01-A035 and C01-A039 . The most notable of these is A-234, which was claimed to be responsible for the poisoning of Sergei and Yulia Skripal in Salisbury (UK) 2018. The detection of OPEs in the air as far away as Antarctica at concentrations around 1 ng/m suggests their persistence in air, and their potential for long-range transport. OPEs were measured in high frequency in air and water and widely distributed in northern hemisphere. The chlorinated OPEs (TCEP, TCIPP, TDCIPP) in urban sampling sites and non-halogenated like TBOEP in rural areas respectively were frequently measured in

O-Ethyl methylphosphonothioic acid - Misplaced Pages Continue

2016-464: The amino acids and fatty acids . Deprotonation of a carboxylic acid gives a carboxylate anion . Carboxylic acids are commonly identified by their trivial names . They often have the suffix -ic acid . IUPAC -recommended names also exist; in this system, carboxylic acids have an -oic acid suffix. For example, butyric acid ( CH 3 CH 2 CH 2 CO 2 H ) is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing

2079-552: The hydroxyl (–OH) group is replaced with a metal cation . For example, acetic acid found in vinegar reacts with sodium bicarbonate (baking soda) to form sodium acetate , carbon dioxide , and water: Widely practiced reactions convert carboxylic acids into esters , amides , carboxylate salts , acid chlorides , and alcohols . Their conversion to esters is widely used, e.g. in the production of polyesters . Likewise, carboxylic acids are converted into amides , but this conversion typically does not occur by direct reaction of

2142-525: The 1930s and is generally credited to Gerhard Schrader . At the time pesticides were largely limited to arsenic salts ( calcium arsenate , lead arsenate and Paris green ) or pyrethrin plant extracts, all of which had major problems. Schrader was seeking more effective agents, however while some organophosphates were found to be far more dangerous to insects than higher animals, the potential effectiveness of others as chemical weapons did not go unnoticed. The development of organophosphate insecticides and

2205-538: The European Union have both been increasing restrictions on organophosphate pesticides since the 1990s, particularly when used for crop protection. The use of organophosphates has decreased considerably since that time, having been replaced by pyrethroids and neonicotinoids , which are effective a much lower levels. Reported cases of organophosphate poisoning in the US have reduced during this period. Regulation in

2268-458: The HCl by-product can react with the phosphate esters to give organochlorides and a lower ester. This reaction is usually undesirable and is exacerbated by high reaction temperatures. It can be inhibited by the use of a base or the removal of HCl through sparging . Esterifications of phosphoric acid with alcohols proceed less readily than the more common carboxylic acid esterifications, with

2331-422: The carboxylic acid and the amine. Instead esters are typical precursors to amides. The conversion of amino acids into peptides is a significant biochemical process that requires ATP . Converting a carboxylic acid to an amide is possible, but not straightforward. Instead of acting as a nucleophile, an amine will react as a base in the presence of a carboxylic acid to give the ammonium carboxylate salt. Heating

2394-405: The context of pesticides, derivatives of organophosphates such as organothiophosphates (P=S) or phosphorodiamidates (P-N) are included as being organophosphates. The reason is that these compound are converted into organophosphates biologically. [REDACTED] In biology the esters of diphosphoric acid and triphosphoric acid are generally included as organophosphates. The reason is again

2457-459: The earliest nerve agents was conjoined, with Schrader also developing the nerve agents tabun and sarin . Organophosphate pesticides were not commercialised until after WWII. Parathion was among the first marketed, followed by malathion and azinphosmethyl . Although organophosphates were used in considerable qualities they were originally less important than organochlorine insecticides such as DDT , dieldrin , and heptachlor . When many of

2520-454: The energy penalty of promoting electrons into the higher energy orbitals being off-set by the stabilisation of additional bonding. Later advances in computational chemistry showed that d-orbitals played little significant role in bonding. Current models rely on either negative hyperconjugation , or a more complex arraignment with a dative -type bond from P to O, combined with back-donation from an oxygen 2p orbital. These models agree with

2583-815: The environment across multiple sites. In the Laurentian Great Lakes total OPEs concentrations were found to be 2–3 orders of magnitude higher than concentrations of brominated flame retardants measured in similar air. Waters from rivers in Germany, Austria, and Spain have been consistently recorded for TBOEP and TCIPP at highest concentrations. From these studies, it is clear that OPE concentrations in both air and water samples are often orders of magnitude higher than other flame retardants, and that concentrations are largely dependent on sampling location, with higher concentrations in more urban, polluted locations. Carboxylic acid In organic chemistry ,

O-Ethyl methylphosphonothioic acid - Misplaced Pages Continue

2646-407: The experimental observations of the phosphoryl as being shorter than P-OR bonds and much more polarised. It has been argued that a more accurate depiction is dipolar (i.e. (RO) 3 P -O ), which is similar to the depiction of phosphorus ylides such as methylenetriphenylphosphorane . However in contrast to ylides, the phosphoryl group is unreactive and organophosphates are poor nucleophiles, despite

2709-622: The field of extractive metallurgy to liberate valuable rare earth metals from their ores . Di(2-ethylhexyl)phosphoric acid and tributyl phosphate are used for the liquid–liquid extraction of these elements from the acidic mixtures form by the leaching of mineral deposits. The same compounds are also used in nuclear reprocessing , as part of the PUREX process. Mono- and di- phosphate esters of alcohols (or alcohol ethoxylates ) act as surfactants (detergents). Although they are very common in biology as phospholipids , their industrial use

2772-399: The final product physically rather than by chemical bond. Due to this, OPEs leak into the environment more readily through volatilization, leaching, and abrasion. OPEs have been detected in diverse environmental compartments such as air, dust, water, sediment, soil and biota samples at higher frequency and concentration. The popularity of OPEs as flame retardants came as a substitution for

2835-562: The first half of the twentieth century in the from of triphenyl phosphate , tricresyl phosphate and tributyl phosphate for use in plastics like cellulose nitrate and cellulose acetate . Use in cellulose products is still significant, but the largest area of application is now in plasticized vinyl polymers, primarily PVC . The more modern organophosphate flame retardants come in 2 major types; chlorinated aliphatic compounds or aromatic diphosphates. The chlorinated compounds TDCPP , TCPP and TCEP are all involatile liquids, of which TCPP

2898-493: The first phosphorus compounds observed to act as cholinesterase inhibitors were organophosphates, the vast majority of nerve agents are instead phosphonates containing a P-C bond. Only a handful of organophosphate nerve agents were developed between the 1930s and 1960s, including diisopropylfluorophosphate , VG and NPF . Between 1971 and 1993 the Soviet Union developed many new potential nerve agents, commonly known as

2961-471: The formation of the anhydride via condensation is an equilibrium process. Under acid-catalyzed conditions, carboxylic acids will react with alcohols to form esters via the Fischer esterification reaction, which is also an equilibrium process. Alternatively, diazomethane can be used to convert an acid to an ester. While esterification reactions with diazomethane often give quantitative yields, diazomethane

3024-740: The gas phase and condensed (solid) phase. Halogenated organophosphates are more active overall as their degradation products interfere with combustion directly in the gas phase. All organophosphates have activity in the condensed phase, by forming phosphorus acids which promote char formation, insulating the surface from heat and air. Organophosphates were originally thought to be a safe replacements for brominated flame retardants, however many are now coming under regulatory pressure due to their apparent health risks. The chlorinated organophosphates may be carcinogenic, while others such as tricresyl phosphate have necrotoxic properties. Bisphenol-A bis(diphenyl phosphate) can hydrolyse to form Bisphenol-A which

3087-576: The general pattern of -ic acid and -ate for a conjugate acid and its conjugate base, respectively. For example, the conjugate base of acetic acid is acetate . Carbonic acid , which occurs in bicarbonate buffer systems in nature, is not generally classed as one of the carboxylic acids, despite that it has a moiety that looks like a COOH group. Carboxylic acids are polar . Because they are both hydrogen-bond acceptors (the carbonyl −C(=O)− ) and hydrogen-bond donors (the hydroxyl −OH ), they also participate in hydrogen bonding . Together,

3150-407: The global south can be less extensive. In 2015, only 3 of the 50 most common crop-specific pesticides used in the US were organophosphates ( Chlorpyrifos , Bensulide , Acephate ), of these Chlorpyrifos was banned in 2021. No new organophosphate pesticides have been commercialised in the 21st century. The situation in vector control is fairly similar, despite different risk trade-offs, with

3213-468: The global use of organophosphate insecticides falling by nearly half between 2010 and 2019. Pirimiphos-methyl , Malathion and Temefos are still important, primarily for the control of malaria in the Asia-Pacific region. The continued use of these agents is being challenged by the emergence of insecticide resistance . Flame retardants are added to materials to prevent combustion and to delay

SECTION 50

#1732802042337

3276-406: The high concentration of charge on the phosphoryl oxygen. The polarisation accounts in part for the higher melting points of phosphates when compared to their corresponding phosphites . The bonding in penta-coordinate phosphoranes (i.e. P(OR) 5 ) is entirely different and involves three-center four-electron bonds . Phosphate esters bearing P-OH groups are acidic . The pKa of the first OH group

3339-582: The highly regulated brominated flame retardants . Organophosphates are a class of compounds encompassing a number of distinct but closely related function groups . These are primarily the esters of phosphoric acid and can be mono‑esters, di‑esters or tri‑esters depending on the number of attached organic groups (abbreviated as 'R' in the image below). In general man‑made organophosphates are most often triesters, while biological organophosphates are usually mono- or di-esters. The hydolysis of triesters can form diesters and monoesters. [REDACTED] In

3402-593: The hydroxyl and carbonyl group form the functional group carboxyl. Carboxylic acids usually exist as dimers in nonpolar media due to their tendency to "self-associate". Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas bigger carboxylic acids have limited solubility due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be soluble in less-polar solvents such as ethers and alcohols. Aqueous sodium hydroxide and carboxylic acids, even hydrophobic ones, react to yield water-soluble sodium salts. For example, enanthic acid has

3465-584: The liver, while in insects they take place in the gut and fat body . As the transformations are handled by different enzymes in different classes of organism it is possible to find compounds which activate more rapidly and completely in insects, and thus display more targeted lethal action. This selectivity is far from perfect and organophosphate insecticides remain acutely toxic to humans, with many thousands estimated to be killed each year due to intentional (suicide) or unintentional poisoning. Beyond their acute toxicity, long-term exposure to organophosphates

3528-476: The most common type of organic acid . Carboxylic acids are typically weak acids , meaning that they only partially dissociate into [H 3 O] cations and R−CO − 2 anions in neutral aqueous solution. For example, at room temperature, in a 1- molar solution of acetic acid , only 0.001% of the acid are dissociated (i.e. 10 moles out of 1 mol). Electron-withdrawing substituents, such as -CF 3 group , give stronger acids (the p K

3591-587: The most important group, with tricresyl phosphate being the first to be commercialised in the 1940s, with trixylyl phosphate following shortly after. Butylphenyl diphenyl phosphate and propylphenyl diphenyl phosphate became available after 1960. In addition to their use as hydraulic base-stock, organophosphates (tricresyl phosphate) and metal organothiophosphates ( zinc dithiophosphate ) are used as both an antiwear additives and extreme pressure additives in lubricants , where they remain effective even at high temperatures. Organophosphates have long been used in

3654-462: The organochlorines were banned in the 1970s, following the publishing of Silent Spring , organophosphates became the most important class of insecticides globally. Nearly 100 were commercialised, with the following being a varied selection: Organophosphate insecticides are acetylcholinesterase inhibitors , which disrupt the transmission of nerve signals in exposed organisms, with fatal results. The risk of human death through organophosphate poisoning

3717-479: The reactions rarely proceeding much further than the phosphate mono-ester. The reaction requires high temperatures, under which the phosphoric acid can dehydrate to form poly-phosphoric acids. These are exceedingly viscous and their linear polymeric structure renders them less reactive than phosphoric acid. Despite these limitations the reaction does see industrial use for the formation of monoalkyl phosphates, which are used as surfactants . A major appeal of this route

3780-415: The salt to above 100 °C will drive off water and lead to the formation of the amide. This method of synthesizing amides is industrially important, and has laboratory applications as well. In the presence of a strong acid catalyst, carboxylic acids can condense to form acid anhydrides. The condensation produces water, however, which can hydrolyze the anhydride back to the starting carboxylic acids. Thus,

3843-674: The spread of fire after ignition. Organophosphate flame retardants are part of a wider family of phosphorus-based agents which include organic phosphonate and phosphinate esters, in addition to inorganic salts. When some prominent brominated flame retardant were banned in the early 2000s phosphorus-based agents were promoted as safer replacements. This has led to a large increase in their use, with an estimated 1 million tonnes of organophosphate flame retardants produced in 2018. Safety concerns have subsequently been raised about some of these reagents, with several under regulatory scrutiny. Organophosphate flame retardants were first developed in

SECTION 60

#1732802042337

3906-425: The transmission of diseases spread by insects, such as mosquitoes. Health concerns have seen their use significantly decrease since the turn of the century. Glyphosate is sometimes called an organophosphate, but is in-fact a phosphonate . Its chemistry, mechanism of toxicity and end-use as a herbicide are different from the organophosphate insecticides. The development of organophosphate insecticides dates back to

3969-605: Was obvious from the start and led to efforts to lower toxicity against mammals while not reducing efficacy against insects. The majority of organophosphate insecticides are organothiophosphates (P=S) or phosphorodiamidates (P-N), both of which are significantly weaker acetylcholinesterase inhibitors than the corresponding phosphates (P=O). They are 'activated' biologically by the exposed organism, via oxidative conversion of P=S to P=O, hydroxylation, or other related process which see them transformed into organophosphates. In mammals these transformations occur almost exclusively in

#336663