80751-37-7Relevant academic research and scientific papers
Catalysis of the ethanolysis of aryl methyl phenyl phosphinate esters by alkali metal ions: Transition state structures for uncatalyzed and metal ion-catalyzed reactions
Onyido, Ikenna,Albright, Kendall,Buncel, Erwin
, p. 1468 - 1475 (2007/10/03)
This paper reports on a spectrophotometric kinetic study of the effects of the alkali metal ions Li+ and K+ on the ethanolysis of the aryl methyl phenyl phosphinate esters 3a-f in anhydrous ethanol at 25°C. Rate data obtained in the absence and presence of complexing agents afford the second-order rate constants for the reaction of free ethoxide (kEtO-) and metal ion-ethoxide ion pairs (kMOEt). The sequence k EtO- MOEt is established for all the substrates, contrary to the generally observed reactivity order in nucleophilic substitution processes. The quantities δGip, δGts and ΔGcat, which quantify the observed alkali metal ion effect in terms of transition state stabilization through chelation of the metal ion, give the order δGts > δGip for Li+ and K+. Hammett plots show significantly better correlation of rates with σ and σo substituent constants than with σ-, yielding moderately large Ρ(Ρo) values that are consistent with a stepwise mechanism in which formation of a pentacoordinate (phosphorane) intermediate is the rate-limiting step. The range of the values of the selectivity parameter, Ρn (= Ρ/Ρeq), 1.3 1.6, obtained for the uncatalyzed and alkali metal ion catalyzed reactions indicates that there is no significant perturbation of the transition state (TS) structure upon chelation of the metal ions. This finding is relevant to the mechanism of enzymatic phosphoryl transfer involving metal ion co-factors. The present results enable one to compare structural effects for nucleophilic reactions of several series of organophosphorus substrates. It is shown that the order of reactivity of the substrates: 4-nitrophenyl dimethyl phosphinate (2) > 3a > 4-nitrophenyl diphenyl phosphinate (1) is determined mainly by the steric effects of the alkyl/aryl substituents around the central P atom in the TS of the reaction. The Royal Society of Chemistry 2005.
Enzymatic resolution of chiral phosphinate esters
Li, Yingchun,Aubert, Sarah D.,Maes, Eugene G.,Raushel, Frank M.
, p. 8888 - 8889 (2007/10/03)
The bacterial phosphotriesterase has been shown to catalyze the stereoselective hydrolysis of phosphinate esters. The wild-type enzyme preferentially hydrolyzes the SP-enantiomers of methyl phenyl p-X-phenylphosphinate esters by 3 orders of mag
Correlation of 31P nuclear magnetic resonance chemical shifts in aryl phosphinates with Hammett substituent constants: Inductive versus resonance interactions and relevance to p? - d? bonding
Dunn, E. J.,Purdon, J. G.,Bannard, R. A. B.,Albright, K.,Buncel, E.
, p. 3137 - 3143 (2007/10/02)
Substituent-induced chemical shifts and coupling constants in the 31P, 13C, and 1H nuclear magnetic resonance spectra of meta- and para-substituted phenyl dimethylphosphinates (1), methylphenylphosphinates (2), and diphenylphosphinates (3) have been deter
