Phosphoric acid and thiophosphoric

Some Preparative and Mechanistic Aspects of the Chemistry of Phosphoric Acid and Thiophosphoric Acid Chloride Betaines... 

Stereochemical data exist for a large number of displacement reactions on neutral phosphoric acid and thiophosphoric acid esters and amides (64). Many of these occur with retention of configuration, especially when the displacement reactions occur on five-membered ring compounds, and this stereochemical course is explained by pseudorotation of a pentacoordinate intermediate. In contrast, only one stereochemical study has been performed on an anionic phosphate ester with the intention of detecting the participation of a phosphorane intermediate. 

Esters of phosphoric acid and thiophosphoric acid can also be detected. A modification of the procedure allows 0.0015 y P to be detected. ... 

Gerrard, W., and Hudson, H. R., Organic Derivatives of Phosphorous Acid and Thiophosphorous Acid, in Organic Phosphorus Compounds, Vol. 5, Kosolapoff, G. M., and Maier, L., eds., 1973, 23-329, Wiley, New York. 

Parathion-methyl is less toxic to humans than the ethyl homologue. This is in agreement with the general experience that dimethyl phosphoric acid and dimethyl thiophosphoric acid derivatives are less toxic to warm-blooded animals than the... 

Tertiary amines serve the dual role of base, to generate the Michaelis-Becker reagent from the parent dialkyl phosphorous or thiophosphorous acid, and subsequently (in the pro-tonated state) as the leaving group for displacement by the anion.179... 

Virtually all that tested positive are methyl or ethyl esters of phosphoric or thiophosphoric acids, and are electrophilic and mutagenic (e.g., dichlorvos, tetrachlorvinphos Figure 14.12). 

Hydrolytic Reactions of Phosphoric and Thiophosphoric Acid Esters... 

Figure 13.17 General structure of phosphoric and thiophosphoric acid (thio)esters. Note that often Ri = R2 = CH3 or C2H5.

Table 13.12 Rate Constants kA, N, and kB, Half-Lives, tu2, at pH 7, and /NB Values for Hydrolysis of Some Phosphoric and Thiophosphoric Acid Triesters at 25°C a...

As for other esters, hydrolysis of phosphoric and thiophosphoric acid triester occurs via acid-catalyzed, base-catalyzed, and neutral mechanisms (Table 13.12). We note that in the following discussion we are concerned primarily with acid triesters, although the hydrolysis products of these compounds, that is, the di- and monoesters, are also of environmental concern inasmuch as they usually seem to react at slower rates as compared to the triesters (Mabey and Mill, 1978 Wolfe, 1980). 

As is unfortunately true for many investigations, the studies reflected by die data shown in Fig. 13.18 did not include analysis for transformation products. Therefore, we may only speculate regarding reaction mechanisms. Nevertheless, we may conclude that when dealing with the hydrolysis of phosphoric and thiophosphoric acid derivatives, as well as with other phosphorus-containing hydrolyzable functionalities (see Fig. 13.19), one has to be aware that various reaction mechanisms may apply. Consequently, depending on the environmental conditions prevailing, product distribution, at least with respect to intermediates formed, may vary considerably. 

As can also be seen from Table 13.12, acid-catalyzed hydrolysis is unimportant for many phosphoric and thiophosphoric acid triesters. Among the exceptions are diax-onon and diazinon (/AN = 6.4 and 5.7, respectively). Try to explain why. 

Only a few papers dealing with monocyclic 1,2,3-triazines have been published, and the number of known compounds of this type is still low. Much more information is available on the 1,2,3-benzotriazines (2) and the first representative of this class was prepared in the last century (1887JPR(35)262>. The increasing interest in the chemistry of (2) is a result of the wide range of biological activity associated with many derivatives of 1,2,3-benzotriazin-4-(3//)-one (3 R=H), and especially of phosphoric and thiophosphoric acid derivatives of (3). 

Thiophosphoric Acid Derivatives. A fortunate combination of characteristics occurs in the phosphoric acid derivatives upon substitution of a sulfur atom for one of the oxygens of the parent compound Namely, the toxicity of the derivatives to higher forms of life is substantially diminished. while at the same rime, (he acaricidal and insecticidal powers, with... 

Aoids (709) 69. Imidodiphosphoric or Imidopyropbosphoric Aoid (712) 70. Amides and Imides of the Higher Phosphoric Acids (714) 71. The Meta-phosphimic Acids and their Salts (716) 72. Phosphorus Chloronitrides or Phosphonitrilic Chlorides (721) 73. Ammonia Derivatives of Thiophosphoric Acid (725). 

Phosphoric acid chloride and thiophosphoric acid chloride pyrididium betaines (I) which are easily prepared by reacting P401Qt P OgS. and P4S1Q, respectively, with phosphorus oxychldride or phdspnorus thio-chloride in the presence of pyridine (1.), are of interest for the synthesis of substituted phosphates and thiophosphates. 

Phosphorus containing additives include esters of phosphoric acids, derivatives of thiophosphoric acids, phosphites (Davey, 1950 Sakuri and Sato, 1970), and the metal salts of dithiophosphoric acid diesters, the best known of these compounds being the ZDDPs. The structure of ZDDP films, the composition of the film formed, and the mechanism of action on the molecular level are summarized in Chapter 4. 

Amido-derivatives of Phosphorous and Orthopbosphoric Acids—Amido- and Imido-derivatives of Metaphosphoric Acid.—Amides and Imides of Condensed Phosphoric Acids—Nitrilophosphoric Acids—Amido-, Imido- and Nitrilo-thiophosphoric Acids—Phosphorus Halonitrides or Amidohalides— Phosphorus Nitride. 

Aliphatic aminoesters of phosphoric (and thiophosphoric) acid react with phosgene. Equation (10.45), under milder conditions (ca. 0 C) than do the aromatic aminoesters. Only... 

Chelates of metal ions with alkyl- and arylphosphoric and thiophosphoric acids can be extracted into chloroform and other solvents [25,26]. Such systems enable one to separate, by means of extraction procedures, many metals from strongly acid solutions. Examples of such reagents are di-(2-ethylhexyl)phosphoric acid (HDEHP) and di-n-butyldithiophosphoric acid (formulae 1.9 and 1.10). HDEHP is a viscous liquid (density 0.98), slightly soluble in water, but readily soluble in benzene, hexane, and MIBK. 

Let us now turn to an example of nucleophilic substitution involving a group of pollutants other than alkyl halides. We consider the hydrolysis of thiometon and disulfoton, two insecticides that were among the major contaminants that entered the Rhine River after the famous accident at Schweizerhalle in Switzerland in 1986 (Capel et al., 1988). This example is representative for the hydrolysis of a variety of phosphoric and thiophosphoric acid derivatives (e.g., esters, thioesters, see Fig. 1), and it illustrates that hydrolysis of a more complex molecule may be somewhat more complicated. The kinetic data, as well as the proposed mechanisms of hydrolysis of thiometon and disulfoton, are presented in Table 4 and Figure 2, respectively. In these cases, the base catalyzed reaction... 

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