Gas-phase mechanisms of degradation of hazardous organophosphorus compounds: do they follow a common pattern of alkaline hydrolysis reaction as in phosphotriesterase?
A comprehensive ab initio analysis of the gas-phase mechanisms of alkaline hydrolysis for a number of phosphotriesterase substrates--O,O-diisopropyl phosphorofluoridate (DFP), O-isopropyl methyl phosphonofluoridate, O,O-diethyl p-nitrophenyl phosphate (paraoxon), O,O-diethyl p-nitrophenyl thiophosphate (parathion), N-acetyl phosphoramidothioate (acephate), O,O-diethyl S-2-ethylthioethyl phosphorothioate (demeton-S) and O-ethyl N,N-dimethyl phosphoramidocyanidate--has been presented herein. The results indicate that, although an associative mechanism of alkaline hydrolysis is followed by all these compounds, P-F and P-CN bonds are cleaved according to the multistep addition-elimination scheme, whereas the breakage of P-O and P-S bonds appears to be consistent with the one-step direct-displacement mechanism. Of the two alternative reaction pathways present in all those cases (except of acephate), the most probable one involves the proton from a nucleophilic hydroxide experiencing an additional stabilization by the phosphoryl oxygen atom.
Dyguda-Kazimierowicz
Edyta
E
Department of Chemistry, Wrocław University of Technology, Wybrzeze Wyspiańskiego 27, 50-370 Wrocław, Poland.
Sokalski
W Andrzej
WA
Leszczynski
Jerzy
J
D005740:Gases; D006868:Hydrolysis; D008958:Models, Molecular; D009943:Organophosphorus Compounds / Q000737:chemistry*; D044345:Phosphoric Triester Hydrolases / Q000737:chemistry*; D013816:Thermodynamics
D005740:Gases; D009943:Organophosphorus Compounds; D044345:Phosphoric Triester Hydrolases