Tire road wear particles (TRWPs) are one of the largest sources of microplastics to the urban environment with recent concerns as they also provide a pathway for additive chemicals to leach into the environment. Stormwater is a major source of TRWPs and associated additives to urban surface water, with additives including the antioxidant derivative N-(1,3dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPDquinone) demonstrating links to aquatic toxicity at environmentally relevant concentrations. The present study used complementary analysis methods to quantify both TRWPs and a suite of known tire additive chemicals (including 6PPD-quinone) to an urban tributary in Australia during severe storm events. Concentrations of additives increased more than 40 times during storms, with a maximum concentration of 2760 ng/L for ∑ 15 additives, 88 ng/L for 6PPD-quinone, and a similar profile observed in each storm. TRWPs were detected during storm peaks with a maximum concentration between 6.4 and 18 mg/L, and concentrations of TRWPs and all additives were highly correlated. Contaminant mass loads to this catchment were estimated as up to 100 g/storm for ∑ 15 additives, 3 g/storm for 6PPD-quinone, and between 252 and 730 kg of TRWPs/storm. While 6PPD-quinone concentrations in this catchment were lower than previous studies, elevated concentrations post storm suggest prolonged aquatic exposure.

The oxidative transformation product of a common tire preservative, identified as N-(1,3-dimethylbutyl)-N′-phenyl-pphenylenediamine quinone (6-PPDQ), has recently been found to contribute to "urban runoff mortality syndrome" in Coho salmon at nanogram per liter levels. Given the number of fish-bearing streams with multiple stormwater inputs, large-scale campaigns to identify 6-PPDQ sources and evaluate mitigation strategies will require sensitive, high-throughput analytical methods. We report the development and optimization of a direct sampling tandem mass spectrometry method for semiquantitative 6-PPDQ determinations using a thin polydimethylsiloxane membrane immersion probe. The method requires no sample cleanup steps or chromatographic separations, even in complex, heterogeneous samples. Quantitation is achieved by the method of standard additions, with a detection limit of 8 ng/L and a duty cycle of 15 min/sample. High-throughput screening provides semiquantitative concentrations with similar sensitivity and a full analytical duty cycle of 2.5 min/sample. Preliminary data and performance metrics are reported for 6-PPDQ present in representative environmental and stormwater samples. The method is readily adapted for realtime process monitoring, demonstrated by following the dissolution of 6-PPDQ from tire fragments and subsequent removal in response to added sorbents.

Cannabichromene (CBC) is unusual among cannabinoids in having been described as both a racemic and a scalemic compound from natural Cannabis sources. Several explanations are available for this circumstance, including facile racemization. Cannabichromene was resolved chromatographically, and the enantiomer matching CBC from local Cannabis was identified. To preclude racemization, CBC was converted to cannabicyclol for further stereochemical analysis. This permitted the (R) absolute stereochemistry to be assigned to natural CBC based on chiroptical data for related natural products and the absolute configuration of a cannabicyclol analog determined by Xray crystallography. The racemization of CBC was found to be rather slow in the laboratory, but handling practices for natural cannabis products can be inferred to promote the process.

Aryl phosphines and dialkylbiaryl phosphines react with singlet oxygen to form phosphinate esters. For mixed arylphosphines, the most electron-rich aryl group migrates to form the phosphinate, while for dialkylbiaryl phosphines migration of the alkyl group occurs. Dialkylbiaryl phosphines also yield arene epoxides, especially in electron rich systems. Phosphinate ester formation is increased at high temperature while protic solvents increase the yield of epoxide. The product distribution provides evidence for Buchwald's recent conformational model for the aerobic oxidation of dialkylbiaryl phosphines.Phosphadioxiranes are highly reactive heteroatom-containing peroxides, and belong to what Greer et al. have aptly called "rather exotic types of cyclic peroxides".1 It is now wellestablished that they are the primary intermediates in the reaction of singlet dioxygen with phosphines.2 , 3 In addition, at very high temperatures, phosphadioxiranes are probably formed during the reaction of triplet dioxygen with phosphines.4 Intermolecular oxygen atom transfer from these highly unstable intermediates to the starting phosphine leads to phosphine oxide formation. In addition to this process, phosphadioxiranes may undergo a variety of interesting reactions, including oxygen atom insertion into the aryl P-C bond to form phosphinate esters, and, in a few cases, arene epoxidation.5 , 2b , 2c Several theoretical studies suggest that phosphadioxiranes should be electrophilic oxidants.3 However, the scope of oxygen atom transfer reactions from phosphadioxirane as well as the regioselectivity, and effects of temperature and solvent are not known. For example, the photooxidation of arylphosphines with different aryl groups attached to the phosphorus atom mselke@calstatela.edu. § Deceased December 28, 2008Supporting Information Available: Experimental procedures, full spectroscopic data for all new compounds, and CIF files for compounds 2 and 3. This material is available free of charge via the Internet at http://pubs.acs.org. has not been studied, i.e. it is not known if the formation of phosphinate esters is regioselective. Furthermore, there have been no reports of photooxidation of several other important classes of phosphines such as phosphines bearing biaryl ligands. Intramolecular oxygen atom insertion into the P-C bond and arene epoxidation might ultimately be useful reactions for the functionalization of such phosphines, if the scope and regioselectivity of these reactions were known, and if the competing intermolecular oxygen atom transfer to form phosphine oxide could be limited. In this paper, we present a detailed investigation of product distribution, regioselectivity, solvent and temperature effects of the reactions of phosphadioxiranes generated from singlet oxygen and a variety of different phosphines. We show that oxygen atom insertion in mixed (i.e. bearing different aryl and/or alkyl groups) phosphines is in fact regioselective. We also investigate how solvent and temperature effects can be used to maxim...