title: Locus-specific microemulsion catalysts for sulfur mustard (HD) chemical warfare agent decontamination.
abstract: The rates of catalytic oxidative decontamination of the chemical warfare agent (CWA) sulfur mustard (HD, bis(2-chlororethyl) sulfide) and a range (chloroethyl) sulfide simulants of variable lipophilicity have been examined using a hydrogen peroxide-based microemulsion system. SANS (small-angle neutron scattering), SAXS (small-angle X-ray scattering), PGSE-NMR (pulsed-gradient spin-echo NMR), fluorescence quenching, and electrospray mass spectroscopy (ESI-MS) were implemented to examine the distribution of HD, its simulants, and their oxidation/hydrolysis products in a model oil-in-water microemulsion. These measurements not only present a means of interpreting decontamination rates but also a rationale for the design of oxidation catalysts for these toxic materials. Here we show that by localizing manganese-Schiff base catalysts at the oil droplet-water interface or within the droplet core, a range of (chloroethyl) sulfides, including HD, spanning some 7 orders of octanol-water partition coefficient (K(ow)), may be oxidized with equal efficacy using dilute (5 wt. % of aqueous phase) hydrogen peroxide as a noncorrosive, environmentally benign oxidant (e.g., t(1/2) (HD) approximately 18 s, (2-chloroethyl phenyl sulfide, C(6)H(5)SCH(2)CH(2)Cl) approximately 15 s, (thiodiglycol, S(CH(2)CH(2)OH)(2)) approximately 19 s {20 degrees C}). Our observations demonstrate that by programming catalyst lipophilicity to colocalize catalyst and substrate, the inherent compartmentalization of the microemulsion can be exploited to achieve enhanced rates of reaction or to exert control over product selectivity. A combination of SANS, ESI-MS and fluorescence quenching measurements indicate that the enhanced catalytic activity is due to the locus of the catalyst and not a result of partial hydrolysis of the substrate.
authors: School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK. fallis@cf.ac.uk
authors: Ian A
authors: IA
authors: Fallis
authors: Peter C
authors: PC
authors: Griffiths
authors: Terence
authors: T
authors: Cosgrove
authors: Cecile A
authors: CA
authors: Dreiss
authors: Norman
authors: N
authors: Govan
authors: Richard K
authors: RK
authors: Heenan
authors: Ian
authors: I
authors: Holden
authors: Robert L
authors: RL
authors: Jenkins
authors: Stephen J
authors: SJ
authors: Mitchell
authors: Stuart
authors: S
authors: Notman
authors: Jamie A
authors: JA
authors: Platts
authors: James
authors: J
authors: Riches
authors: Thomas
authors: T
authors: Tatchell
mesh_terms: D002384:Catalysis; D002619:Chemical Warfare Agents / Q000737:chemistry* / Q000302:isolation & purification; D003666:Decontamination / Q000379:methods*; D004655:Emulsions; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009151:Mustard Gas / Q000737:chemistry* / Q000302:isolation & purification; D033363:Neutron Diffraction; D009821:Oils / Q000737:chemistry; D010084:Oxidation-Reduction; D053838:Scattering, Small Angle; D012995:Solubility; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D002619:Chemical Warfare Agents; D004655:Emulsions; D009821:Oils; D014867:Water; D009151:Mustard Gas