Chemical Environment of Phosphorus

In order to identify the chemical nature of phosphorus and sulfur in complex matrices such as antiwear tribofilms, it is essential to compare the spectra of films with different model compounds in which the local chemical environments of phosphorus and sulfur are known. The high resolution of the technique allows characterization of the chemical nature of phosphorus and sulfur in the tribofilm. Investigators have shown that the chain length of polyphosphate is related to the length of alkyl groups in ZDDP. By comparison of the L-edge XANES spectra of the tribofilms with the spectra of model compounds with known structures, it has been possible to speciate the chemical nature of phosphorus and sulfur in the antiwear tribofilms. 

Both isomers lack symmetry elements and, consequently, the two three-coordinate phosphorus atoms are inequivalent. The chemical environments of the two P(III) centres are similar in both isomers, but the large value of /ab=263 Hz indicates a P-P bond as found in 3.11b. ... 

The main difference between XPS and XANES, as Fig. 4.1. indicates, is the fact that the features of the peaks a-d (relative intensities and positions) change from one compound to another. For example, the chemical state and the local environment of phosphorus in orthophosphate (Zn3(P04)2) pyrophosphate... 

In the XANES technique, it is essential to compare spectra of films with those of different model compounds in which the local chemical environments of the phosphorus and the sulfur are known (Brown et al., 1992 Fuller et al., 1998). 

Faust SD, Gomaa HM. 1972. Chemical hydrolysis of some organic phosphorus and carbamate pesticides in aquatic environments. Environ Lett 3 171 -201. 

The 3IP NMR chemical shifts, shown in Table IV, should be a useful indicator of the electronic environment at phosphorus. Almost all the 3IP chemical shifts are upfield (negative 8 values) in contrast to the boron-phosphorus compounds where downfield shifts (positive 8 values) are observed. This can be interpreted in terms of weak gallium-phosphorus it-... 

The difference in chemical shift can be attributed to a significant change to the local environment of the phosphorus where the O-P-O angle may change from 95° to 117° and changes in P-N bond lengths can be expected. Low-temperature NMR has indicated the presence of more than two isomers for related compound 117 (R = Me and Et) when in solution <20040L145>. 

Degradation of parathion in soil was by hydrolysis to p-nitro-phenol and diethylthiophosphoric acid and reduction to aminopara-thion (25,26). Chemical oxidation of parathion in soils and waters was not prevalent, although oxidation of the phosphorus-sulfur bond has been shown to occur under ultraviolet light and in oxidizing environments (26). At ordinary levels of application to soil, parathion was degraded within weeks if microbial activity was available (27). Accumulations even after repeated applications were unlikely (28). When higher concentrations were applied to soil, persistence increased. Simulated spills of concentrated parathion resulted in a 15% residue after five years (29) and 0.1% after 16 years (30). 

Melnick, R.L. Tomaszewski, K.E. (1990) Triethanolamine. In Buhler, D.R. Reed, D.J., eds, Ethel Browning s Toxicity and Metabolism ofIndustrial Solvents, Vol. II, Nitrogen and Phosphorus Solvents, Amsterdam, Elsevier, pp. 441-450 Morin, R.J. Lim, C.T (1970) Inhibition in vitro of incorporation of [ P]-phosphate into rabbit and human endometrial phospholipids. J. reprod. Fert., 23, 456-462 Mortelmans, K., Haworth, S., Lawlor, T., Speck, W., Tainer, B. Zeiger, E. (1986) Salmonella mutagenicity tests II. Results from the testing of 270 chemicals. Environ, mol. Mutag., 8 (Suppl. 7), 1-119... 

The results presented here concern two classes of organophos-phorus molecules denoted class a] and class b). In class a], one considers a set of cyclic thioxo-phosphonates of different size, five to eight-membered rings 1, 2, 3, 4, and in which the chemical environment at the phosphorus remains the same -.O p S. ( 7). 

The reaction of indole with pyrocatechol chlorophosphite (5), in which the electrophilicity of the phosphorus atom is higher than in dialkyl chlorophosphites, leading to an increase in the proportion of C(3)-phosphorylated compounds, was studied in order to explain the effect of the environment of the P(III) atom on the direction of phosphorylation [18]. In fact, according to the P NMR data, the reaction product 6 gives only one signal with a chemical shift of 128 ppm, indicating reaction at position 3 ... 

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