Houshang J. Foroudian

Reduction of o-iodosobenzoate ion by sulfides and its oxidative regeneration

o-Iodosobenzoate and o-iodoxybenzoate ion (IBA and IBX, respectively) are turnover catalysts of hydrolyses of phosphonofluoridates and non-toxic simulants. Reactions of IBA with phosphonothioates are stoichiometric because sulfides (e.g. 4-methoxybenzenethiol) reduce IBA to o-iodobenzoate ion. Oxidants, e.g. , as OXONE, and magnesium peroxyphthalate, MPPA, regenerate IBA and gradually oxidize it to IBX, which eventually decomposes. The procedure was tested on hydrolyses of p-nitrophenyl diphenylphosphate (pNPDPP) and 4-nitrobenzenesulfonyl fluoride, 1, catalyzed by IBA, and the catalyzed hydrolysis of 1 was examined. Some of the oxidation products of 4-methoxybenzene thiol were identified by 1H NMR spectroscopy and oxidative decomposition of IBX was monitored. Periodate ion slowly oxidized o-iodobenzoate ion to IBA and IBX. Copyright

Unexpected stoichiometry in the cleavage of bis(4-nitrophenyl) phosphate and 4-nitrophenyl phosphorochloridate by alkaline hydrogen peroxide

Reaction of alkaline hydrogen peroxide with bis(4-nitrophenyl) phosphate ion proceeds with simultaneous liberation of ca 2 equiv. of 4-nitrophenol per mole of substrate, and no evidence for build-up of an intermediate. Reaction of HO2− with the more activated 4-nitrophenyl phosphorochloridate gives 4-nitrophenol in up to 40% yield with simple first-order kinetics and no indication of a long-lived intermediate. A fast intramolecular nucleophilic displacement of 4-nitrophenolate ion by peroxide in the initially formed 4-nitrophenyl peroxophosphate is proposed to explain this behavior. Copyright

Sulfide oxidation and oxidative hydrolysis of thioesters by peroxymonosulfate ion

Peroxymonosulfate ion, HSO5–, as OXONE, in aqueous MeCN readily converts aryl thiobenzoates, XC6H4CO·SC6H4Z (X =p-OMe, p-Me, H, p-Cl, p-CN; Z=p-OMe, p-Me, H, m-OMe, p-Cl, m-Cl, p-NO2) into carboxylic and sulfonic acids. Reactions are second order and have small substituent effects, with p≈–0.6 based on σm and σp substituent parameters, but rates increase markedly with increasing water content in aqueous MeCN and entropies of activation are negative. The initial step is very similar to the oxidation of methyl aryl sulfides by HSO5– which has similar solvent and substituent effects. Enthalpies of activation are much lower for oxidation of the sulfides than of the corresponding esters but entropies of activation are similar.

Nucleophilicity of bromide ion in mixed cationic/sulfoxide micelles

Addition of the non-ionic surfactant, n-decyl methylsulfoxide (C10SO) to aqueous cetyltrimethylammonium bromide (CTABr) inhibits the micellar-mediated reaction of Br– with bound methyl naphthalene-2-sulfonate (MeONs). The concentration of Br– at the micellar surface is reduced due to an increase in the fractional micellar ionization, α, and in the volume of the micellar pseudophase, which slows the reaction of Br–. These concentration effects are partially offset by an increase in the second-order rate constant in the micellar pseudophase on addition of C10SO.