Organophosphorus parameters

The spectral parameters of 15a and other silicon-organophosphorus betaines described henceforth in Section 2.2.2 allowed us to show reliably that the reaction of phosphorus ylides with thiocarbonyl compounds, unlike the classical Wittig reaction, occurs through the intermediate formation of betaines (17)11 (Scheme 9). Erker and coworkers performed a more detailed... 

The parameters of organophosphorus betaines 5, 6,15,17, 20, 21, 24, 25, and 31 and the corresponding phosphonium cations R3P+ CHR1] 2, as well as cations of silylated phosphonium salts R CHR -SiR2,82 84 are quite similar. The 31P NMR signals of the betaines lie in the region typical of tetracoordinated phosphorus.85,86... 

In this chapter, an attempt has been made to address fundamental mechanistic and kinetic aspects of TiO2 photocatalysis of organophosphorus compounds. Comparisons between homogeneous (radiolysis) and heterogeneous (photocatalysis) hydroxyl-generating processes have helped to elucidate the reaction pathways and led to number of important mechanistic conclusions. From the various kinetic parameters, the overall rates and efficiencies for the degradation of organophosphorus compounds can be predicted and may find direct application in evaluation and implementation of semiconductor photocatalysis. 

Additional methods considered for 304(h) rule making and the parameters measured are the following (the numbers in parentheses indicate the number of compounds included in the method) 622, organophosphorus pesticides (19) 623, 4,4 -methylene bis(2-chloroaniline) 626, acrolein and acrylonitrile (2) 627, dinitroaniline pesticides (5) 628, carbofuran 629, cyanazine 630, dithiocarbamates (15) 631, carbendazim and benomyl 632, carbamate and urea pesticides (7) and 633, organonitrogen pesticides (7). Most of these are... 

Stable organophosphorus Jt-radicals were observed for some derivatives of l,3-diphosphetane-2,4-diyls 6. A reversible electrochemical or chemical oxidation of 6c-e leads to electron paramagnetic resonance (EPR)-active radicals, whose spectroscopic parameters were elucidated (Figure 1) <1996TH1, 1998TH1>. 

Reliable pATa values are not often available, although reasonable estimates ( 1 unit) can be calculated. Kabachnik and Mastryukova showed that the Hammett equation is applicable to organophosphorus acids, deriving substituent constants for substituents on phosphorus. These are claimed " to be superior to Hammett/Taft parameters. ... 

The synthesis, structures and reactivity of a series of silicon-containing organophosphorus betaines which have a P-C-Si-S or P-C-C-S skeleton have been reported and the changes in the geometric parameters of the betaines depending on the substituents at the phosphorus, carbon and silicon atoms analysed. ... 

In the heterocycle 16, P and Se high-resolution solid-state NMR spectroscopy was used to study structural properties. Both P CP/MAS and Se CP/ MAS experiments revealed that the asymmetric unit consists of two independent molecules with a different geometry around phosphorus and selenium centres. The established values of anisotropy and asymmetry parameters reflected the distortion of the phosphorus environment, and correlated with X-ray diffraction data. P NMR spectroscopy has been used to follow a new type of P-decomposi-tion in diphosphorylated amines and to characterise new organophosphorus compounds with -N-P(0)-N- linkages. A series of dioxaphosphocin-6-oxides (17), of varying substituent X, have been characterised by using P NMR and... 

The same descriptor correlated well also with the acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzyme inhibition activity of organophosphorus compounds. The best one-parameter correlation for the toxicity of organophosphorus compounds was achieved by using the normalized electronic moment (Me) [46]. 

Clayton and Purcell have illustrated the predictive utility of this method when applied to selected butyrylcholinesterase inhibitors (94). They obtained quantitative correlations using group dipole moments, and /x in addition to hydrophobic parameters. In addition, Hansch and co-workers have used Taft steric parameters (Es) (60) and pKa values to obtain excellent correlations in various systems (84). E8 has recently been shown to be quantitatively related to van der Waal s radii for symmetrical top-like substituents (98) while pKa values have been used as a measure of electron density distributions (99). Fukuto and co-workers combined Tafts Es and a parameters in a physicochemical approach to the mode of action of organophosphorus insecticides (95). 

The number of diffraction studies of phosphorus compounds continues to increase. A timely review of the geometric parameters of acyclic organophosphorus compounds has been published. ... 

At —60° in ether, high yields of phosphonites were obtained provided the reaction mixture was distilled directly and not hydrolyzed (102). Dilute aqueous acid readily hydrolyzes phosphonites—a fact which could reduce the efficiency of the Grignard synthesis (53). Experiments by others have supported these suspicions (100,104,176). Probably of equal importance is the use of tetrahydrofuran as a solvent which appears to improve the yields in the cases cited. Improved solvation of the Grignard reagent and the organophosphorus products may be influential. Double displacement of OR occurs at 40° with dibutyl vinylphosphonite which demonstrates the importance of the temperature parameter (99). Even the reactive phosphinite (17) survives at... 

Table 7 Kinetic Parameters (Particle Diffusion and Mass Transfer Constant) Calculated for the Different Organophosphorus-Containing Impregnated Resins...

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