Solvent Effects on Reactions of Hydroxide and Oximate Ions With Phosphorus(v) Esters

Abstract

Second-order rate constants of reactions of OHϪ , 2,3-butanedionemonooximate and 2-hydroxybenzaldoximate ions with aryl phosphate, phosphinate and thioarylphosphinate esters go through minima with decreasing water content of aqueous acetonitrile, tert-butyl alcohol and N-methyl-2-pyrrolidone. For reactions in H 2 O-MeCN the solvent effects are analyzed in terms of activity coefficients of the anionic nucleophiles and transition states. In the drier solvents partial desolvation of the nucleophiles increases rates. Nucleophilicities of several oximates and inorganic anions are compared in water.

para‐ and ortho‐Pyridinium aldoximes in reaction with acetylthiocholine

“…AChE has the key role in cholinergic neurotransmission and exposure to even small amounts of an organophosphorus (OP) compound (nerve warfare agents and some pesticides) can be fatal due to its inhibition by phosphylation. Only a few studies on the chemical and physical properties of aldoximes have been published by now [4][5][6][7][8] although a detailed understanding of the structural features of these compounds is an important step in the search for more effective antidotes.…”

“…The pH-dependant absorption spectra were determined for aldoximes and pK a values were calculated. We evaluated the nucleophilic property of the oxime group of the aldoximes by studying their reaction with the AChE substrate acetylthiocholine iodide (ATCh) (oximolysis), because the mechanism of nucleophilic substitution by oxime is analogue to the aldoxime nucleophilic attack on both phosphylated AChE and ATCh [5]. Oximolysis was measured at different pH to confirm involvement of the oxime anion, oximate, in the nucleophilic attack.…”

Detection of chemical warfare simulants by phosphorylation of a coumarin oximate

“…One approach that has been studied uses chromogenic detector reagents, which directly bind to, or react with, a target nerve agent, causing a modulation in the absorbance spectra. [5][6][7][8] Recently, Rebek developed a fluorescent sensor based on a PET quenching mechanism of a fluorophore that upon cyclization produced a strong fluorescent signal. 9 A very similar concept was also developed by Timothy Swager in 2003.…”