Dephosphorylation and aromatic nucleophilic substitution in nonionic micelles. The importance of substrate location

Abstract

Reactions of OH- and F- with p-nitrophenyl diphenyl phosphate (pNPDPP) are inhibited by very dilute dodecyl (10) and (23) polyoxyethylene glycol (C12E10 and C12E23, respectively), but rate constants become independent of surfactant concentrations at concentrations above the critical micelle concentration. Low charge density anions, e.g., ClO4-, inhibit and low charge density cations, e.g., (n-C7H15)4N+, accelerate reactions, probably by controlling concentrations of nucleophiles in the palisade layer. Diphenyl phosphorofluoridate, generated by attack of F-, is not detected but is rapidly hydrolyzed to phenyl phosphorofluoridate or diphenyl phosphate ion with loss of phenol or F-. The products are different in DMSO containing modest amounts (<15 vol%) of water and no surfactant and are phenyl phosphorofluoridate and difluorophosphate ions generated by attack of F- on the initial phosphorofluoridate. These differences are consistent with the micellar palisade layer being water-rich. Although the nonionic surfactants do not intervene nucleophilically in reactions of pNPDPP, considerable amounts of ether are formed in the reaction of 2,4-dinitrochlorobenzene (DNCB), in C12E10 and C12E23 at high pH by attack of alkoxide ion with the relatively hydrophilic DNCB located close to the micellar surface. The differences in the chemistries of reactions of pNPDPP and DNCB appear to be associated largely with differences in locations of these substrates in the nonionic micelles.Key words: fluoridates, p-nitrophenyl diphenyl phosphate, 2,4-dinitrochlorobenzene, nonionic micelles, palisade layer.

New Anions of Pentacoordinate Phosphorus Containing Fluorine and Trifluoromethyl Groups

“…NMR investigations of 1:1 mixtures of (PhO) 3 [11,12] The characteristic NMR spectroscopic data for the compounds 4, 5 (Table 1) and 6 are in full agreement with the data given by Christe et al [8] The main advantage of the [F 4 PO] -anion synthesis starting from triphenylphosphate is the relative stability of this anion in the solid state as well as in dmso solution at 20°C. This result supports the suggestion that the presence of excess P(O)F 3 used in the known procedure significantly accelerates the dismutation process.…”

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

“…Therefore there are differences in the factors that govern inhibition by anionic and nonionic micelles, and probably hydrophobic substrates enter a region of the latter in which hydrophilic ions are partially excluded, but more hydrophilic substrates remain close to the micellar surfaces and are exposed to hydrophilic ions (2,3,6,9).…”

“…This group could attack a phosphate ester at high pH, because its pK a should be similar to that of ethane-1,2-diol, which is 14.8 (13), and the corresponding alkoxide ions are effective nucleophiles in micelles and microemulsions (14,15), but reaction of p-nitrophenyl diphenyl phosphate with the terminal group of nonionic micelles was found to be unimportant (16). However, labile ethers form in reactions with a less hydrophobic substrate, 2,4-dinitrochlorobenzene (9).…”

“…Loss of the p-nitrophenoxide ion is the major reaction of p-nitrophenyl diphenyl phosphate, but there is a minor loss of phenoxide ion (9,14,16), and we therefore examined reactions of p-nitrophenyl diphenyl phosphinate ( p-NPDP) (Scheme 1).…”

“…The surfactants used in the present work are dodecyl-polyoxyethylene ethers, C 12 E 10 and C 12 E 23 (Brij35), n ϭ 9 and 22, respectively: (9), but tosylate and naphthalene-2-sulfonate ion and ClO 4 Ϫ inhibit, and tetra-n-heptylammonium ion accelerates, reactions. We planned to examine salt effects on reactions of p-NPDP with OH Ϫ and F Ϫ .…”