Micellar rate effects on reactions of hydroxide ion with phosphinate and thiophosphinate esters

Abstract

Cationic micelles of cetyltrimethylammonium chloride, bromide and mesylate (CTACI, CTABr, CTAOMs) speed reactions of OH-with phosphinate and thiophosphinate esters: PhzPO.OPh (la), PhzPO.OC6H4N0z-p (lh), Ph(i-Pr)PO.OCsH4NOz-p (lc), PhzPO.SEt (2a), Ph2PO.SPh (2b), (Et0)zPO.SPh (2c) and (EtO)zPS.OCaH4NOz-p (Parathion, 3). First-order rate constants go through maxima with increasing [ surfactant 1. The rate-surfactant profiles are fitted quantitatively in terms of a kinetic model that treats the distribution of OH-between aqueous and micellar pseudo-phases in terms of coulombic and non-coulombic ion-micelle interactions. Second-order rate constants at the micellar surface are lower than in water by factors that range from 0-035 for l a to 0.7 for lc. The thiophenyl derivative (2b) is more reactive than the corresponding phenoxy derivative (la) and it is more reactive than the corresponding thioethyl derivative (2a). Parathion (3) is the least reactive substrate in both water and miceltes. R'2PO.SR (2a) R' = Ph, R = Et (2b) R' = R = P h ( 2~) R' = OEt, R = Ph

Surfactant effects on the reaction of 2‐(4‐cyanophenoxy)‐quinoxaline with hydroxide ion

“…It is known that quaternary ammonium headgroups interact favorably with arenes [7,13]. Submicellar aggregates are involved in some nucleophilic aromatic [8] and heteroaromatic [1,2] substitution reactions, and in the attack of OH − on thiophosphinates [14] where double rate maxima are observed in rate versus surfactant profiles.…”

Reactions of p-Nitrophenyl Diphenyl Phosphinate with Fluoride and Hydroxide Ion in Nonionic Micelles: Kinetic Salt Effects

“…Reaction products were identified by their 1 H, 19 F, and 31 P NMR spectra (9,18), generally with 0.01 M p-NPDP in DMSO-d 6 , DMSO-d 6 (20). Although F Ϫ , like OH Ϫ , is a very hydrophilic ion, which "salts out" organic solutes and increases their activity coefficients (21), changes in its concentration do not significantly affect values of k 2 in water.…”

“…1 H chemical shifts were referred to DMSO (␦ ϭ 2.50 ppm) or to TSP (4, 4-dimethyl-4-silapentanoic acid, sodium salt), 19 F chemical shifts were referred to CF 3 Cl by using external CF 3 CO 2 H (␦ ϭ Ϫ76.55 ppm), and 31 P chemical shifts were referred to external 85% H 3 PO 4 (␦ ϭ 0 ppm).…”

“…Reaction products were identified by their 1 H, 19 F, or 31 P NMR spectra monitored generally on Varian Unity instruments (400 or 500 MHz for 1 H). 1 H chemical shifts were referred to DMSO (␦ ϭ 2.50 ppm) or to TSP (4, 4-dimethyl-4-silapentanoic acid, sodium salt), 19 F chemical shifts were referred to CF 3 Cl by using external CF 3 CO 2 H (␦ ϭ Ϫ76.55 ppm), and 31 P chemical shifts were referred to external 85% H 3 PO 4 (␦ ϭ 0 ppm).…”

Enhanced nucleophilic reactivity of hydroxamate ions in some novel micellar systems for the cleavage of Parathion

“…The rate enhancements with [surfactant] can be treated quantitatively in terms of pseudophase model [21,22] (Scheme 2) that provide estimates of second order rate constants at surfaces of colloidal assemblies by calculating concentrations of both reagents at the surfaces.…”