Phosphonylation rate constant

Addition of phosphonyl radicals onto alkenes or alkynes has been known since the sixties [14]. Nevertheless, because of the interest in organic synthesis and in the initiation of free radical polymerizations [15], the modes of generation of phosphonyl radicals [16] and their addition rate constants onto alkenes [9,12,17] has continued to be intensively studied over the last decade. Narasaka et al. [18] and Romakhin et al. [19] showed that phosphonyl radicals, generated either in the presence of manganese salts or anodically, add to alkenes with good yields. 

Selected entries from Methods in Enzymology [vol, page(s)] Types of organophosphorus inhibitors, 11,686-688 toxicity hazards, 11,688 purity and analysis, 11,688 solutions of organophosphorus compounds, 11,689 estimation of specific radioactivity of organophosphorus compounds, 11,689-690 method for estimating phosphorus content, 11,691 reactions with enzymes, 11,691 -701 [rate constants, 11,692 phosphorylation of chymotrypsin, 11, 694-696 identification of phosphoryl and phosphonyl peptides,... 

The second-order rate constant for the reaction between sarin and either 2-PAM I or II was found to be 170 L/mol per minute. If a phosphorylated or phosphonylated oxime that does not enter rapidly into the second step above is formed, that product may be an Inhibitor of cholinesterase. 7,88 Hydrolysis of sarin in the presence of 200-fold concentrations of V and II took place more rapidly in plasma from rats with the former oxime than with the... 

The overall progress of the reaction from E-OH and inhibitor to phosphonylated enzyme is characterized by the bimolecular rate constant of inhibition, ki. This important measure of inhibitory potency is determined by measuring the activity remaining as a function of time of preincubation with various concentrations of inhibitor. The substrate is... 

The phosphonylated enzyme can undergo spontaneous reactivation via hydrolysis to yield free enzyme and a phosphonic acid, with an associated pseudo-first-order rate constant, (the reactivator, water, is present in great excess). The spontaneous rate constant of reactivation, k, can be obtained from the relationship... 

A review has recently been published on the subject Phosphorus Radicals . Once again e.s.r. spectroscopy has proved to be an invaluable tool for investigating the kinetics of reactions of phosphorus radicals. Thus the rate constants for the bimolecular reactions of several types of phosphorus radicals, e.g. phosphinyl, phosphonyl, and phosphoranyl radicals, with like species have been determined and shown to be of the same order as, or very close to, the diffusion-controlled limit.These annihilation reactions presumably involve formation of a P—P-bonded dimer. An interesting observation recorded in the paper reporting this work was that t-butoxyl radicals react with (25) to give phosphinyl radicals. 

Et0)2P=0 radicals, obtained from t-BuO and (Et0)2P(H)=0, abstract halogen from alkyl halides, with competition studies being used to establish relative rates. Absolute second-order rate constants for reaction with butyl halides are 10 times slower for the phosphonyl radical compared with Et3Si. Phosphinyl-radical intermediates are implicated from ESR and P cidnp experiments when ketoximato-phosphorus(III) intermediates (formed from ketoximes and X2PCI at low temperatures) rearrange... 

Table 7 Bimolecular Rate Constants (1 mol sec of the Reaction of Phosphonyl and Benzoyl Radicals with Various Monomers in Cyclohexane at 20°C...

TABLE 2. BIMOLECULAR RATE CONSTANTS" CYCLOHEXANE AT ROOM TEMPERATURE FOR THE REACTION OF PHOSPHONYL RADICALS WITH VARIOUS MONOMERS IN... 

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