Reaction of tris(2-chloroethyl)phosphate with reduced sulfur species

Tris(2-chloroethyl)phosphates (TCEP) is a widely used flame retardant in the US. It has recently been identified as one of the most frequently detected contaminants in US streams. This contaminant is of toxicological concern in sensitive coastal ecosystems such as estuaries and salt marshes. It is likely that reactions with reduced sulfur species such as polysulfides (Sn2-), bisulfide (HS−), and thiophenolate (PhS−) present in anoxic subregions of coastal water bodies could have a significant impact on rates of removal of such a contaminant. The kinetics of reaction of reduced sulfur species with tris(2-chloroethyl)phosphate have been determined in well-defined aqueous solutions under anoxic conditions. Reactions were monitored at varying concentrations of reduced sulfur species to obtain the second-order rate constants from the observed pseudo-first-order rate constants. The determined second-order rate constant for the reaction of TCEP with polysulfide at 25 °C is 5.0 (±1.4) × 10−4 M−1 s−1, with thiophenolate at 50 °C is 34 (±2) × 10−4 M−1 s−1 and with bisulfide at 50 °C is 0.9 × 10−4 M−1 s−1, respectively. In addition, the degradation products of hydrolysis and the reactions with polysulfides, thiophenolate, and bisulfide with TCEP were studied with GC–FID and LC–MS–MS and were quantified.

► Reaction of tris(2-chloroethyl)phosphates with reduced sulfur species were investigated.
► Reaction rates of TCEP with polysulfides, bisulfide, and thiophenolate were determined.
► Major degradation product of this reaction is bis(2-chloroethyl)phosphate.
► Sulfur species are sufficiently reactive as to control fate of TCEP in anoxic environments.