Doris S. Tse

Photolysis of nitroaromatics in aquatic systems. I. 2,4,6-trinitrotoluene

Abstract Photolysis of 2,4,6-trinitrotoluene (TNT) occurs rapidly in pure and natural waters irradiated with sunlight, with half-lives of less than a half-hour in some natural waters. Experiments to study the TNT photolysis products and to obtain evidence for complexation of TNT with natural substances are discussed.

Hydrothermal treatment and the oxygen functionalities in Wyodak coal

The effects of hydrothermal treatment (liquid water) at 350 °C on Argonne-supplied Wyodak coal previously ‘dried’ at 60 °C under 1 torr for 18 h were studied. Control experiments were conducted in the absence of added water, and with n-undecane replacing water. All runs were conducted in batch reactors with quartz liners for periods of 30 min or 5 h with added N2 (500 psi cold), and product workups and all manipulations were conducted in an N2 glove bag. A tar representing 5–7% of the starting coal was deposited on the quartz walls solely for hydrothermal conditions. In all cases the coal lost oxygen, the O-losses being in the order: undecane < no added water (30 min) = added water (30 min) = no added water (5 h) < added water (5 h). Thermal gravimetric and field ionization mass spectrometer (f.i.m.s.) analyses (ambient to 500 °C at 2.5 °C min−1) showed little difference between the experiments with undecane and those with no added water. By contrast, hydrothermal treatment yielded a volatiles fraction that was at the same time more volatile and had a greater weight average molecular weight. Phenol, catechol, and their C1-, C2-, and C3-derivatives were the two most prominent families in the f.i.m.s.-volatiles spectra, and the f.i.m.s. responses showed that under added water conditions the catechols response was increased. With undecane in place of water, the precursors to the f.i.m.s.-volatile arenols engaged primarily in regressive chemistry. The exhaustive (5 h) hydrothermal treatment resulted in virtual elimination of both phenol and catechol signals, demonstrating extensive hydrolysis of the coal structure. The results are consistent with a scheme in which water promotes the production of the tar, removing it from the coal matrix. The organic medium, on the other hand, suppresses the diffusion of thermally generated fragments, and they become irreversibly reincorporated. The O-losses are due primarily to CO2- and H2O-evolution. The data suggest that the latter is largely due specifically to catechol dehydroxylation.

Catalytic synthesis of oligosilazanes part 2

Abstract Preliminary studies on transition metal-catalyzed dehydrocoupling of Si-H bonds with H-N bonds to form Si-N bonds, silazanes and H 2 are described. A number of transition metal complexes have been tested as catalyst precursors for the dehydrocoupling reaction. Of these, Ru 2 (CO) 8 -(Et 3 Si) 2 proved to be the most active homogeneous catalyst, and Pd particles produced by the in situ reduction of Pd(OAc) 2 were the most active heterogeneous catalysts. Kinetic studies of the ruthenium-catalyzed reaction of Et 3 SiH with primary amines, RNH 2 (R = n-Pr, n-Bu, s-Bu and t-Bu) were run at 70 °C in THF. The effects of changes in Et 3 SiH, amine and catalyst concentrations on rates of reaction were examined. The data indicate that the dehydrocoupling catalytic cycle involves an extremely complex set of equilibria wherein the rate-determining step is dependant on the steric requirements of the amine and fragmentation of the starting Ru 3 (CO) 12 cluster.

Fate of diethylene glycol dinitrate in surface waters

Abstract The environmental fate of diethylene glycol dinitrate (DEGDN) in surface waters is dominated by photolysis with surface half-lives ranging from 15 days in summer to 59 days in winter at 40°N. The environmental quantum yield is 0.18. Photolysis of DEGDN initially forms nitrate ion and 2-hydroxyethyl nitratoacetate; the latter photolyzes further to 1- and 2-carbon acids and additional nitrate. DEGDN biotransforms with a second-order rate constant of 3.9 × 10−11 mL cell−1 h−1, corresponding to a half-life of about 2 years in a typical surface water. Intermediate biotransformation products were observed but were further transformed and did not accumulate. DEGDN is expected to move readily through soils because it had low soil sorption coefficients Kp of 2 and 0.8 g mL−1 on EPA-5 and EPA-18 sediments, respectively. Abiotic reduction occurred rapidly in lake and river sediments but the importance of this process for overall fate is difficult to quantitate. Other fate parameters measured at 25°C were a water solubility of 3900 mg L−1, octanol/water partition coefficient of 9.6 (dimensionless), Henrys constant of