Documents disponibles écrits par cet auteur

Efficient methanolytic cleavage of phosphate, phosphonate, and phosphonothioate esters promoted by solid supported lanthanide ions / Tamer Andrea in Industrial & engineering chemistry research, Vol. 49 N° 15 (Août 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 7027–7033 Titre : Efficient methanolytic cleavage of phosphate, phosphonate, and phosphonothioate esters promoted by solid supported lanthanide ions Type de document : texte imprimé Auteurs : Tamer Andrea, Auteur ; Alexei A. Neverov, Auteur ; R. Stan Brown, Auteur Année de publication : 2010 Article en page(s) : pp 7027–7033 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Methanolytic  Phosphate  Ions. Résumé : The methanolyses of three neutral organophosphorus esters, namely paraoxon (O,O-diethyl O-p-nitrophenyl phosphate (12), O-ethyl O-p-nitrophenyl methylphosphonate (13), O-ethyl S-3,5-dichlorophenyl methylphosphonothioate (14, a model for VX), and an anionic phosphonate ester, O-hydrogen S-3,5-dichlorophenyl methylphosphonothioate (15, a model for a toxic hydrolytic decomposition product of VX known as EA2192)), promoted by solid supported lanthanide ion catalysts (La3+, Sm3+, Eu3+, Yb3+) were investigated at 25 °C under sspH controlled conditions in methanol. The supports were derived from commercially available chlorobenzylated silica and chloromethylated polystyrene functionalized with two chelating ligands, iminodiacetic acid (IDA) and ethylenediamine-N,N′-diacetic acid (EDDA), followed by exposure to Ln3+ ions. The catalysts showed good activity at two investigated sspH values of 8.8 and 11 (in methanol). Despite the fact that the methoxide promoted reactions for the four substrates span a range of 20000-fold, the apparent second order rate constants (k2app) for methanolysis of these promoted by the solid supported lanthanide catalysts were rather insensitive to the nature of the support (Si or polystyrene), Ln3+ ion, substrate, and sspH. The Yb3+ complex of IDA on silica (Si/IDA/Yb) gave the highest k2app values of 6.6 and 14.4 M−1 s−1 for 12 and 13, 48.8 M−1 s−1 for 14, and 2.6 M−1 s−1 for 15 at sspH 11. The acceleration of cleavage of 13 at sspH 8.8 by the Si/IDA/Yb catalyst at an apparent concentration of 4.8 mM (50 mg suspended in 2.5 mL of methanol) is about 8.5 × 105 faster than the methoxide reaction at that sspH. The acceleration of the cleavage of 14 and 15 by 50 mg of Si/IDA/Yb at sspH 11 is 6.3 × 105- and 5 × 108-fold relative to the methoxide promoted reaction at that sspH. The matrixes containing the smaller lanthanide ions like Eu and Yb could be recycled at least eight times without loss of activity. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1008458 [article] Efficient methanolytic cleavage of phosphate, phosphonate, and phosphonothioate esters promoted by solid supported lanthanide ions [texte imprimé] / Tamer Andrea, Auteur ; Alexei A. Neverov, Auteur ; R. Stan Brown, Auteur . - 2010 . - pp 7027–7033. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 7027–7033 Mots-clés : Methanolytic  Phosphate  Ions. Résumé : The methanolyses of three neutral organophosphorus esters, namely paraoxon (O,O-diethyl O-p-nitrophenyl phosphate (12), O-ethyl O-p-nitrophenyl methylphosphonate (13), O-ethyl S-3,5-dichlorophenyl methylphosphonothioate (14, a model for VX), and an anionic phosphonate ester, O-hydrogen S-3,5-dichlorophenyl methylphosphonothioate (15, a model for a toxic hydrolytic decomposition product of VX known as EA2192)), promoted by solid supported lanthanide ion catalysts (La3+, Sm3+, Eu3+, Yb3+) were investigated at 25 °C under sspH controlled conditions in methanol. The supports were derived from commercially available chlorobenzylated silica and chloromethylated polystyrene functionalized with two chelating ligands, iminodiacetic acid (IDA) and ethylenediamine-N,N′-diacetic acid (EDDA), followed by exposure to Ln3+ ions. The catalysts showed good activity at two investigated sspH values of 8.8 and 11 (in methanol). Despite the fact that the methoxide promoted reactions for the four substrates span a range of 20000-fold, the apparent second order rate constants (k2app) for methanolysis of these promoted by the solid supported lanthanide catalysts were rather insensitive to the nature of the support (Si or polystyrene), Ln3+ ion, substrate, and sspH. The Yb3+ complex of IDA on silica (Si/IDA/Yb) gave the highest k2app values of 6.6 and 14.4 M−1 s−1 for 12 and 13, 48.8 M−1 s−1 for 14, and 2.6 M−1 s−1 for 15 at sspH 11. The acceleration of cleavage of 13 at sspH 8.8 by the Si/IDA/Yb catalyst at an apparent concentration of 4.8 mM (50 mg suspended in 2.5 mL of methanol) is about 8.5 × 105 faster than the methoxide reaction at that sspH. The acceleration of the cleavage of 14 and 15 by 50 mg of Si/IDA/Yb at sspH 11 is 6.3 × 105- and 5 × 108-fold relative to the methoxide promoted reaction at that sspH. The matrixes containing the smaller lanthanide ions like Eu and Yb could be recycled at least eight times without loss of activity. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1008458