Alkyl and aryl phosphates

Murray [91] has described a gas chromatographic method for the determination in water of triarylphosphate esters (Imol S-140, tricresyl phosphate, cresol phosphate). iTtese substances are used commercially as lubricant oil and plastic additives, hydraulic fluids and plasticisers. The method involves extraction from the samples, hydrolysis and measurement of the individual phenols by gas chromatography as the trimethylsilyl derivatives. The lower detection limit was about 3ppm. 

A gas chromatograph with flame ionisation detectors was used for the analysis and the column used was 2.4m x 3mm stainless steel packed with 5% Imol on Chromosorb W, AW and SCMS treated 80-100 mesh. A temperature programme from 80-120°C at 4°C min was used. 

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Another growing technique is super-critical fluid chromatography. Recent references to soil analysis include the following applications aliphatic hydrocarbons, polyaromatic hydrocarbons, polychlorobiphenyls, dioxins, alkyl and aryl phosphates, chloro, organophosphorus, triazine, substituted urea, phenoxy acetic acid, Dacthal herbicides and insecticides and mixtures of herbicides and pesticides and mixtures of organic compounds. 

Chloroanisole Polychlorobiphenyls Chlorodibenzo-p-dioxins and chlorodibenzofurans Basic nitrogen compounds Alkyl and aryl phosphates... 

The serine group which becomes phosphorylated does not appear to possess any marked nucleophilic reactivity, nor is there any evidence that a histidine group participates as a general acid-general base catalyst. Rate constants for the nonenzymic hydrolysis of alkyl and aryl phosphate monoanions at 25° are in the range HP7 to 10-9 sec-1 (167), while the comparable alkaline phosphatase-catalyzed values (in this case they refer to dianions) are in the range 102 to 103 sec-1. Thus one has to account for a rate enhancement factor of 109 to 1012. Moreover, the... 

The metallic soaps of barium, cadmium, lead, and calcium are commonly used as stabilizers. They are HCl acceptors, but their reaction products often cause cloudiness in clear formulations. Alkyl and aryl phosphates are often used with them to inhibit precipitation of insoluble chlorides. Tin complexes have also been used successfully. 

Its metabolism in rats was investigated by Menn and co-workers (1976), demonstrating that the activation is initiated by P=S-+P=0 conversion (oxon formation), while detoxification resulted from hydrolysis of the alkyl and aryl phosphate ester group, as well as from cleavage of the C=N and O—C bond of the oxime carbamate moiety. 

TABLE 11-13. FOUR-BALL EVALUATION OF ALKYL AND ARYL PHOSPHATES... 

APs are nonspecific metalloenzymes that hydrolyze phosphate monoesters optimally at alkaline pH. They liberate inorganic phosphate from many types of molecules including nucleotides, proteins and other biomolecules, and synthetic alkyl and aryl phosphate esters. Probably the most-studied phosphatase of all is the AP from... 

Organophosphorus compounds (OPs) are utilized on a large scale as flame retarding agents and plasticizers in a variety of products, such as plastic materials, rubbers, varnishes, lubricants, hydraulic fluids, and other industrial applications. This family of chemicals consists of alkylated and arylated phosphate or phosphonate esters and related compounds such as phosphites, phosphines, and related dimeric forms as well as ionic forms (Figure 31.2). " The low volatility of phosphoric acid and derivatives makes it the preferred choice of the phosphorus based FRs. These FRs are most effective in polymers that char readily. Also halogenated phosphate esters, such as tris(l-chloroisopropyl) phosphate (TCPP), and tris(2-chloroethyl) phosphate (TCEP), are widely used. These combine the properties of both the halogen and the phosphorus compounds. 

The oxidation of pol5nners is also catalyzed by certain metal ions, which can exist in two oxidation states, e.g. copper, iron, cobalt. These ions exhibit a pre-oxidant effect by stimulating the decomposition of hydroperoxides. Metal deactivators are employed to form complex compounds with them. The metal ions are partially or fully deactivated and the polymer is stabilized. Alkyl and aryl phosphates are used for polymer stabilization (see Table 1). 

A vast number of organophosphorus compounds have been proposed as flame retardants. Alkyl and aryl phosphates are well-known plasticizers for PVC and also have a flame retardant effect. Organophosphorus compounds, sometimes also containing chlorine or bromine, are also... 

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