Phosphates, esters

D-Ribulose 5-phosphate is found together with D-ribose 5-phosphate as an oxidation product of n-gluconic acid 6-phosphate with a purified yeast enzyme (221-223). The D-ribulose 5-phosphate was identified as the o-nitrophenylhydrazone derivative, having a specific rotation in methanol of 50 5°. D-Ribulose 5-phosphate appears to be the precursor of D-ribose in yeast and rat liver. A D-ribulose diphosphate was detected in the products formed during the first few seconds of photosynthesis (224)  

An extract has been prepared from spinach leaves which catalyzes the formation of D-ribulose diphosphate from adenosine triphosphate and D-ribose 5-phosphate (225). The D-ribulose diphosphate appears to be an intermediate in a carbon dioxide fixation system in which D-ribose 5-phosphate was the added substrate (226). 

The action of an enzyme, transketolase, from rat liver or from spinach, on pentose 5-phosphate results in the formation of a triose phosphate and an ester of sedoheptulose, which is presumably sedoheptulose 7-phosphate. The heptulose has been identified by the preparation of sedoheptulosan tetrabenzoate (227). 

Sedoheptulose diphosphate is formed from sedoheptulose 7-phosphate and D-fructose 1,6-diphosphate in the presence of the enzymes aldolase and transaldolase (228). One of its two phosphate groups is relatively labile 

D-Erythrose 4-phosphate has been synthesized and shown to condense with dihydroxyacetone phosphate in the presence of aldolase to give a heptulose diphosphate with properties similar to the one described above 229 ), The synthetic tetrose phosphate is optically inactive, and is decomposed by acid at a rate similar to glyceraldehyde 3-phosphate. 

The most important thiophosphate esters can be separated through TLC on various types of layer, using various solvents. 

Batjmlbr and Rippstbin [6] have chromatographed on silica gel G, using solvent I (Table 140). They detected with a palladium chloride solution (Rgt. No. 193). Salo [79] has developed with toluene. 

Fischbr and Klingblhollbr [31] describe the toxicological detection and the necessary isolation from organs and body fluids. They chromatographed also on silica gel G layers, using the standard method with chamber saturation but at higher temperature (30—31° C). The length of run was 12 cm and solvents were methylene dichloride-methanol-10% ammonium hydroxide solution (60+ 35 + 5) and (80 + 20 + 3), i. e., solvent II of Table 140. 

The analysis of breakdown products and metabolites of insecticides is also important. With the help of TLC, ELalTZ [44] has identifled the products of degradation (e. g., benzamide) of phosphate esters. Kovac [50] has utilised preparative TLC to detect some contaminants of 

Sumithion (Bayer 41831) (see also Petschik [72]). Blinn [9] has midertaken the identification of oxidation products of phorate (in the Thimet mixture) in plant residues he chromatographed on silica gel G layers, using chloroform-methanol (98.2 + 1.8) and toluene-acetonitrile-nitromethane (45 + 40 + 15)- 

Known phosphoric esters, particularly orthophosphate esters, are extremely numerous. Many of these esters play a central role in life processes, although not all are naturally occurring or of direct biological interest. When life cells synthesise or transform an organic compound, frequently, the first step is to convert it into its phosphate ester. 

The first laboratory synthesis of a phosphate ester was carried out by Lassaigne in 1820 [8]. Phosphate esters find numerous applications as plasticisers, flame retardants, reagents for the preparation of organophosphorus polymers, in solvent extraction of heavy metal cations, as insecticides, and in nerve gases (Chapter 12). 

Esters of phosphoric acid are classified according to the number of ester groups present. 

Triesters are entirely covalent compounds which do not occur naturally. Mono- and diesters contain ionizable hydrogen atoms which can be replaced by metallic or non-metallic cations (5.288). Many biological substances are mono- or diesters where R can be very complex. 

Instead of forming salts, mono- and diesters can undergo an internal transfer of protons to form zwitterions. 

Currently there is considerable interest in developing artificial esterases and peptidases that hydrolyse esters and amides. The first nonenzymatic, catalytic hydrolysis of methyl acetate and acetylcholine in neutral water at 25 has now been described. The complex [Co(trpn)(OH)(OH2)] (10) catalyzes the hydrolysis of methyl acetate at pH 7.6. The reaction is believed to involve the steps shown 

The hydrolysis of 2,4-dinitrophenylphosphate (DNPP) to orthophosphate and 2,4-dinitrophenolate is accelerated in the presence of excess [Co(pn)2(OH2)2] or [Co(trpn)(OH2)2] at rates which vary with pH in a manner suggesting that the hydroxoaquatetraamine cobalt(III) complex is the active catalyst (pn = trimethylenediamine trpn = 3,3, 3 -triaminotripropylamine). Detailed mechanistic schemes are proposed. For the trpn complex at pH 6.0 and a 25 1 cobalt-to-DNPP ratio (5 x 10 M DNPP) the observed rate enhancement is - 3 x 10 -fold. The calculated specific rate constant for hydrolysis in the reactive 1 1 complex (k 0.2 s ) represents a rate acceleration of some 3 x lO -fold. 

The nickel(II)-containing enzyme jack bean urease catalyzes the hydrolysis of urea to ammonia and carbon dioxide [Eq. (3)] by a factor of lO at pH 7.0 and 38 °C. As it is believed that coordination of urea to Ni(II) is fundamental to 

They are a versatile surfactant type, with some properties analogous to those of ether sulphates. Unlike sulphate (which is a sulphuric acid mono alkyl ester), phosphate can form di- and triester, giving a wider range of structures and, with them, the ability to tailor the product to a greater number of application areas. 

The esters can be used as acids, but are also often used as sodium or potassium salts. With such a wide potential for structure and properties, it is difficult to draw general properties for the whole class. They are more stable to hydrolysis than are sulphates and can be used across a wide range of pH and temperatures, but other properties are highly dependent on the degree of esterification and the alcohol used. 

Raw materials. The alcohols used in PE manufacture are typically detergent alcohols but shorter chains may also be used. Ethoxylated alcohols, used as non-ionic surfactants in their own right, can also be phosphated to give a surfactant with properties intermediate between non-ionic and sulphated anionic. The provenance of the alcohols has already been covered in detail in the Section 4.2. 

Applications. As medium foaming/hydrotropic surfactants, PEs can be used in detergent cleansing applications with the short chain alkyl esters being effective hydrotropes for nonionic surfactants. Application of PEs in detergents is relatively limited, due to their cost compared to a sulphate/sulphonate, or non-ionic but long chain diesters can be used as effective de-foamers in anionic systems. 

Phosphate esters are widely used in metalworking and lubricants. A C12 h with 6 mol of ethylene oxide (diester) can be used as an emulsifier but also as an extreme pressure additive - it can reduce wear where there is high pressure metal to metal contact. PEs can also show corrosion inhibiting properties, as with petroleum sulphonates and the emulsifying power of PEs with low foam is used in agrochemical formulations. PEs can act as dispersants or hydrotropes in plant protection formulations, allowing the development of easy-to-handle and dilute formulations of both poorly miscible and insoluble herbicides. 

Application Dedusting agent for dry cleaning detergent, alkaline powders, water-repellent fabric finishes. Used in emulsion polymerization for formation of polyvinyl acetate and acrylic films. 

Application Imparts hard-surface detergency, retardation of corrosion, and moderate foaming when used in detergent concentrates. Useful dry cleaning detergent. Compatible with electrolyte solutions. Antistat for textiles. 

Application Used as a softener and antistatic agent in textile finishing. Useful in lubricants for filament yarns, synthetic fibers, and wool. May be used to emulsify cosmetic oils and creams, and for the polymerization of latices. 

Application Used as a textile wetting agent, and in alkaline scouring operations. Used in dry cleaning detergents as potassium or sodium salts. Good antistat properties. 

Application Higher electrolyte tolerance than DESOPHOS 3DP. May be used as a dry cleaning detergent, penetrant, and antistatic agent. 

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Perhaps the most extensively studied catalytic reaction in acpreous solutions is the metal-ion catalysed hydrolysis of carboxylate esters, phosphate esters , phosphate diesters, amides and nittiles". Inspired by hydrolytic metalloenzymes, a multitude of different metal-ion complexes have been prepared and analysed with respect to their hydrolytic activity. Unfortunately, the exact mechanism by which these complexes operate is not completely clarified. The most important role of the catalyst is coordination of a hydroxide ion that is acting as a nucleophile. The extent of activation of tire substrate througji coordination to the Lewis-acidic metal centre is still unclear and probably varies from one substrate to another. For monodentate substrates this interaction is not very efficient. Only a few quantitative studies have been published. Chan et al. reported an equilibrium constant for coordination of the amide carbonyl group of... 

Inspired by the many hydrolytically-active metallo enzymes encountered in nature, extensive studies have been performed on so-called metallo micelles. These investigations usually focus on mixed micelles of a common surfactant together with a special chelating surfactant that exhibits a high affinity for transition-metal ions. These aggregates can have remarkable catalytic effects on the hydrolysis of activated carboxylic acid esters, phosphate esters and amides. In these reactions the exact role of the metal ion is not clear and may vary from one system to another. However, there are strong indications that the major function of the metal ion is the coordination of hydroxide anion in the Stem region of the micelle where it is in the proximity of the micelle-bound substrate. The first report of catalysis of a hydrolysis reaction by me tall omi cell es stems from 1978. In the years that... 

If alkyl groups are attached to the ylide carbon atom, cis-olefins are formed at low temperatures with stereoselectivity up to 98Vo. Sodium bis(trimethylsilyl)amide is a recommended base for this purpose. Electron withdrawing groups at the ylide carbon atom give rise to trans-stereoselectivity. If the carbon atom is connected with a polyene, mixtures of cis- and rrans-alkenes are formed. The trans-olefin is also stereoseiectively produced when phosphonate diester a-carbanions are used, because the elimination of a phosphate ester anion is slow (W.S. Wadsworth, 1977). 

We shall shortly discuss methods i, ii, and iii, which cover the chemistry of phosphate esters, and then describe in more detail methods iv, v, and vi, which are routinely used today. 

Step 2 The ketone carbonyl of the acetoacetyl group is reduced to an alcohol function This reduction requires NADPH as a coenzyme (NADPH is the phosphate ester of NADH and reacts similarly to it)... 

Hydrolysis of the phosphate ester function of the phosphatidic acid gives a diacylglycerol which then reacts with a third acyl coenzyme A molecule to produce a triacylglycerol... 

In keeping with its biogenetic origin m three molecules of acetic acid mevalonic acid has six carbon atoms The conversion of mevalonate to isopentenyl pyrophosphate involves loss of the extra carbon as carbon dioxide First the alcohol hydroxyl groups of mevalonate are converted to phosphate ester functions—they are enzymatically phosphorylated with introduction of a simple phosphate at the tertiary site and a pyrophosphate at the primary site Decarboxylation m concert with loss of the terti ary phosphate introduces a carbon-carbon double bond and gives isopentenyl pyrophos phate the fundamental building block for formation of isoprenoid natural products... 

Nucleic acids are acidic substances present m the nuclei of cells and were known long before anyone suspected they were the primary substances involved m the storage transmission and processing of genetic information There are two kinds of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) Both are complicated biopolymers based on three structural units a carbohydrate a phosphate ester linkage between carbohydrates and a heterocyclic aromatic compound The heterocyclic aro matic compounds are referred to as purine and pyrimidine bases We 11 begin with them and follow the structural thread... 

In the example shown the 5 OH group is phosphorylated Nucleotides are also possible in which some other OH group bears the phosphate ester function Cyclic phosphates are common and important as biochemical messengers... 

Nucleotide (Section 28 3) The phosphate ester of a nucleo side... 

Lubricants, Fuels, and Petroleum. The adipate and azelate diesters of through alcohols, as weU as those of tridecyl alcohol, are used as synthetic lubricants, hydrauHc fluids, and brake fluids. Phosphate esters are utilized as industrial and aviation functional fluids and to a smaH extent as additives in other lubricants. A number of alcohols, particularly the Cg materials, are employed to produce zinc dialkyldithiophosphates as lubricant antiwear additives. A smaH amount is used to make viscosity index improvers for lubricating oils. 2-Ethylhexyl nitrate [24247-96-7] serves as a cetane improver for diesel fuels and hexanol is used as an additive to fuel oil or other fuels (57). Various enhanced oil recovery processes utilize formulations containing hexanol or heptanol to displace oil from underground reservoirs (58) the alcohols and derivatives are also used as defoamers in oil production. 

Pentabromodiphenyl Oxide. Pentabromodiphenyl oxide [32534-81-9] (PBDPO) is prepared from diphenyl oxide by bromiaation (36). It is primarily used as a flame retardant for flexible polyurethane foams. For this appHcation PBDPO is sold as a blend with a triaryl phosphate. Its primary benefit ia flexible polyurethanes is superior thermal stabiUty, ie, scorch resistance, compared to chloroalkyl phosphates (see Phosphate esters). 

T. W. Lapp, The Manufacture and Use of Selected Aryl and Alkyl Aryl Phosphate Esters, Report NTIS PB-251678, Midwest Research Institute, Feb. 1976. 

CeUulose phosphate esters are also produced by treatment with sodium hexametaphosphate [14550-21-1] by the pad-dry-cure technique. These treated fabrics have high retention of breakiag and tearing strength (61). The reaction products contain more than 1.6% phosphoms and are iasoluble ia cupriethylenediamine [15243-01 -3] iadicating that some ceUulose cross-linking occurs. However, siace durable-press (DP) levels and wrinkle recovery values are low, it seems reasonable that only limited cross-linking takes place. 

The hydroxyl groups on glycols undergo the usual alcohol chemistry giving a wide variety of possible derivatives. Hydroxyls can be converted to aldehydes, alkyl hahdes, amides, amines, a2ides, carboxyUc acids, ethers, mercaptans, nitrate esters, nitriles, nitrite esters, organic esters, peroxides, phosphate esters, and sulfate esters (6,7). 

The largest volume of hydrauHc fluids are mineral oils containing additives to meet specific requirements. These fluids comprise over 80% of the world demand (ca 3.6 x 10 L (944 x 10 gal))- In contrast world demand for fire-resistant fluids is only about 5% of the total industrial fluid market. Fire-resistant fluids are classified as high water-base fluids, water-in-oil emulsions, glycols, and phosphate esters. Polyolesters having shear-stable mist suppressant also meet some fire-resistant tests. 

Phosphate Esters. Phosphate esters are one of the larger volume classes of synthetic base fluids. A typical phosphate ester stmcture where R can be either an aryl or alkyl group is... 

SHF, phosphate esters, siUcones sihcones, organic esters, SHF... 

Halogenated hydrocarbons that are inexpensive sometimes are used alone or in blends with phosphate esters as fire-resistant hydrauHc fluids. Other halogenated fluids are used for oxygen-compressor lubricants, lubricants for vacuum pumps that are in contact with corrosive materials, solvent-resistant lubricants, and other lubricant appHcations where highly corrosive or reactive materials are being handled. 

Synthetic oils have been classified by ASTM into synthetic hydrocarbons, organic esters, others, and blends. Synthetic oils may contain the following compounds diaLkylben2enes, poly(a-olefins) polyisobutylene, cycloaUphatics, dibasic acid esters, polyol esters, phosphate esters, siUcate esters, polyglycols, polyphenyl ethers, siUcones, chlorofluorocarbon polymers, and perfluoroalkyl polyethers. 

The reactivity of the individual O—P insecticides is determined by the magnitude of the electrophilic character of the phosphoms atom, the strength of the bond P—X, and the steric effects of the substituents. The electrophilic nature of the central P atom is determined by the relative positions of the shared electron pairs, between atoms bonded to phosphoms, and is a function of the relative electronegativities of the two atoms in each bond (P, 2.1 O, 3.5 S, 2.5 N, 3.0 and C, 2.5). Therefore, it is clear that in phosphate esters (P=0) the phosphoms is much more electrophilic and these are more reactive than phosphorothioate esters (P=S). The latter generally are so stable as to be relatively unreactive with AChE. They owe their biological activity to m vivo oxidation by a microsomal oxidase, a reaction that takes place in insect gut and fat body tissues and in the mammalian Hver. A typical example is the oxidation of parathion (61) to paraoxon [311-45-5] (110). 

Neutral Extractants. Many neutral organophosphoms extractants are available phosphate esters, phosphonate esters, phosphinate esters, and phosphine oxides. The most popular neutral extractant is tributylphosphate (TBP), which reacts with RE elements according to a solvation mechanism ... 

Alkylated aromatic lubricants, phosphate esters, polyglycols, chlorotrifluoroethylene, siUcones, and siUcates are among other synthetics that came into production during much that same period (28,29). Polyphenyl ethers and perfluoroalkyl polyethers have followed as fluids with distinctive high temperature stabiUty. Although a range of these synthetic fluids find appHcations which employ their unique individual characteristics, total production of synthetics represent only on the order of 2% of the lubricant market. Poly(a-olefin)s, esters, polyglycols, and polybutenes represent the types of primary commercial interest. 

Phosphate Esters. A variety of phosphate esters are used as synthetic lubricants, particularly because of their good fire resistance. They have the general formula OP(OR)2, where R may represent a variety of aryl or alkyl hydrocarbon groups containing four or more carbon atoms to give three broad classes triaryl, trialkyl, and aryl alkyl phosphates (37,38). 

Inefficiencies ia the reaction with POCl leads to alternative production of trialkyl phosphates by employing the sodium alkoxide rather than the alkyl alcohol itself Dialkyl aryl phosphates are produced ia two steps. The low molecular weight alcohol iavolved (eg, butyl) first reacts with excess POCl. The neutral phosphate ester is then completed by the iatermediate chloridate reacting with excess sodium arylate ia water. 

Phosphate ester fluids are the most fire resistant of moderately priced lubricants, are generally excellent lubricants, and are thermally and oxidatively stable up to 135°C (38). Fire-resistant iadustrial hydrauHc fluids represent the largest volume commercial use. AppHcations are made ia air compressors and continue to grow for aircraft use (tributyl and/or an alkyl diaryl ester) and ia hydrauHc control of steam turbiaes ia power generation (ISO 46 esters). 

Triaryl phosphates of ISO 32 viscosity show promise for the main beating lubricants of steam and gas turbiaes (39,40). An interesting possibiHty iavolves unique deHvery of phosphate ester vapor to lubricate the piston ring 2one of low heat rejection (adiabatic) diesel engines (41). 

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