Lanthanum ion catalysis of nucleophilic displacement reactions of monoesters of methyl phosphonic acid

Abstract

The catalytic effects of lanthanum ion on the rate of hydrolysis of p-nitrophenyl hydrogen methylphosphonate in aqileous solution at pH >7.0 are reported. Increases in rate by a factor of about 3.6 x lo4 have been observed. No such catalysis was found for diesters of methylphosphonic acid.

Nanosized Reactors Based on Polyethyleneimines: From Microheterogeneous Systems to Immobilized Catalysts

“…Although ammines of Cu and other transition metals are commonly used, we concentrated on using lanthanum ions, for which a considerable acceleration comparable with the ferment effect on the reaction under study was found in our and other publications. [39][40][41][42][43][44][45]68 The kinetics of hydrolysis of 1 and 2 and also the pH changes of the PEI solution with lanthanum ion concentration are plotted in Figures 6-9 for the PEI-800-La(III) and PEI-50-La(III) systems. The results obtained for the PEI-25-La(III) system are similar to those for the PEI-50 based solution; therefore, only the latter are discussed here as an example.…”

“…PEI is known to accelerate the hydrolysis of phosphorus acid esters via general basic catalysis. , Besides, it contributes to the catalysis of the reaction due to the sorption of reagents and to the formation of the substrate−polymer catalytic complex. The modification of the system with La(III) ions makes it possible for the electrophilic catalysis to contribute to the catalytic mechanism, since a considerable acceleration of nucleophilic substitution at phosphorus by lanthanum ions is well-known. − The addition of sodium dodecyl sulfate (SDS) to the systems opens up additional opportunities for binding the reagent due to the solubilization mechanism together with the sorption pattern.…”

“…The modification of the system with La(III) ions makes it possible for the electrophilic catalysis to contribute to the catalytic mechanism, since a considerable acceleration of nucleophilic substitution at phosphorus by lanthanum ions is well-known. [39][40][41][42][43][44][45] The addition of sodium dodecyl sulfate (SDS) to the systems opens up additional opportunities for binding the reagent due to the solubilization mechanism together with the sorption pattern.…”

Recent Studies of Nucleophilic, General-Acid, and Metal Ion Catalysis of Phosphate Diester Hydrolysis

“…This value was calculated on the basis of the data in the literature (ref ) using the p K a value of 9.06 for H 2 O ligated to La 3+ .…”

Metal Cation Micelle Mediated Hydrolysis of Phosphonic Acid Esters

“…Various nucleophiles have been examined as hydrolytic reagents toward PNPMP, including hydroperoxide, hydroxamate, fluoride, thiophenylate, and hypochlorite; hydroperoxide ( k 2 = 2.6 × 10 -3 M -1 s -1 at 30 °C) was the most reactive species . Metal cation mediated cleavage of PNPMP was observed with Ca 2+ (12-fold acceleration), whereas La 3+ , the pyridine-2-carbaldehyde oxime chelate of Y 3+ (acting as a polymeric hydrate), and the 1,1,2,2-tetramethyl-1,2-diaminoethane chelate of Co(III) each afforded very substantial rate accelerations with this substrate . Additionally, La 3+ cations enhanced the hydrolysis of PNPPP ( 4 ) 100-fold (pH 7.4, 60 °C), whereas the transition metal cations Cu 2+ , Ni 2+ , and Zn 2+ were ineffective …”