Phosphate triesters concentrations

Macroreticular resins, particularly the Amberlite XAD series, have been used extensively to isolate and concentrate trace organic compounds from drinking water (1-8). We have previously reported the use of an XAD cartridge for this purpose and have evaluated the system for the analysis of organophosphorus pesticides (OPs) (4), polynuclear aromatic hydrocarbons (PAHs) (5), phosphate triesters (TAAPs) (6), or-... 

The first term, representing acid-"catalyzed" hydrolysis, is important in reactions of carboxylic acid esters but is relatively unimportant in loss of phosphate triesters and is totally absent for the halogenated alkanes and alkenes. Alkaline hydrolysis, the mechanism indicated by the third term in Equation (2), dominates degradation of pentachloroethane and 1,1,2,2-tetrachloroethane, even at pH 7. Carbon tetrachloride, TCA, 2,2-dichloropropane, and other "gem" haloalkanes hydrolyze only by the neutral mechanism (Fells and Molewyn-Hughes, 1958 Molewyn-Hughes, 1953). Monohaloalkanes show alkaline hydrolysis only in basic solutions as concentrated as 0.01-1.0 molar OH- (Mabey and Mill, 1978). In fact, the terms in Equation(2) can be even more complex both elimination and substitution pathways can operate, leading to different products, and a true unimolecular process can result from initial bond breaking in the reactant molecule. 

The reactions of a phosphate triester, p-nitrophenyl diphenyl phosphate with hydroxide and fluoride ions has been demonstrated to be catalyzed strongly by cationic surfactants and inhibited by NaLS and a non-ionic surfactant (Bunton and Robinson, 1969a Bunton et al., 1969, 1970). Hexadecyltrimethylammonium bromide (CTAB) increased the second-order rate constant for the reaction ofp-nitrophenyl diphenyl phosphate with hydroxide ion by a maximum factor of approximately 11 and that with fluoride ion by a maximum factor of approximately 33 at CTAB concentrations of 3 x 10 m and 2 x 10 m respectively. At higher detergent concentrations the catalysis became progressively less pronounced (Fig. 11). This behavior does not fit equation (10) (Bunton and Robinson, 1969a). However, a number of other micelle-catalyzed reactions between anions and neutral molecules have been found to... 

The reactions in cationic micellar media between the a-nucleophile salicylhydroxa-mate anion (SHA ) and p-nitrophenyl benzoate (PNPB), tris(3-nitrophenyl) phosphate (TRIS), and bis(2,4-dinitrophenyl) phosphate (BDNPP) were examined kinetically. SHA was incorporated into CTAB micelles and accelerated dephosphorylation of TRIS over the pH range 6.7—11.4. At 1.0 mM SHA in CTAB, the nucleophilicity of SHA followed the order of reactivity, PNPB (C=0, carboxylate ester) > TRIS (phosphate triester) > BDNPP (phosphate diester) monoanionic SHA and dianionic SHA are the reactive species. The critical micelle concentration of CTAB decreased and the fractional ionization constant, a, increased with an increase in the concentration of SHA . ... 

The rate of hydrolysis of arsenate(V) triesters OAs(OR)3 is much faster than that of phosphate triesters, and decreases in the order R = Me, Et, -pentyl, and isopropyl. Rate constants for the first hydrolysis have been measured, and estimated for the second stage. The third step could not be followed by use of the stopped flow technique. Studies in solvent-water mixtures with varying water concentrations confirm the involvement of water in the rate law. An associative mechanism is postulated with a five-coordinate intermediate OAs(OR)3(OH2). 

A variety of external plasticizers have also been suggested for cyanoacrylates. Among these are alkyl esters of aliphatic monocarboxylic acids such as cyanoacetates aliphatic dicarboxylic esters, such as malonates, adipates, and sebacates triaromatic phosphates such as tricresyl phosphate acyl triesters of glycerine dialkyl alkylphosphonates and alkyl phthalates. Joyner and Coover state that limiting the plasticizer concentration to less than 5% will not retard the cure speed, from 5 to 20% will retard the cure rate, and over 20% plasticizer concentration seriously slows the cure rate of the adhesive. 

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