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In this laboratory experiment, students explore the aquatic photochemical fate of ranitidine and cimetidine, two common pharmaceutical pollutants found in wastewater. It provides an engaging environmental context for students to develop knowledge of reaction kinetics and photochemistry as well as skill in using analytical instrumentation. This versatile experiment consists of two basic modules, three optional advanced modules, and additional add-ons that may be performed in various combinations to meet the unique learning objectives of general, analytical, physical, and environmental chemistry courses and science outreach activities. It may be performed as a traditional lab experiment or as an entirely remote exercise with an increased focus on data analysis and interpretation using provided example data sets. All of the photolysis experiments are carried out by preparing solutions of ranitidine or cimetidine in various matrices, irradiating the samples, and periodically removing subsamples for HPLC analysis of the compound of interest. Pseudo-first order kinetic plots are then generated to determine rate constants that are used to draw conclusions about photolysis pathways or to calculate additional kinetic parameters. In the two basic modules, cimetidine is found to degrade appreciably only when irradiated in the presence natural organic matter (NOM), indicating an indirect, photosensitized degradation pathway. In contrast, ranitidine degrades in pure buffer and in the presence of NOM with comparable rate constants, highlighting the predominant role of direct photolysis. In the advanced modules, students calculate ranitidine direct photolysis quantum yields and examine the significance of singlet oxygen as a photochemically produced reactive intermediate. The two basic modules may be completed in two 3 hour lab periods, while the advanced modules require additional time. This experiment requires only an HPLC instrument, inexpensive chemicals, and common glassware and lab equipment if performed in person and a personal computer if performed remotely.

Health-relevant microorganisms present in natural surface waters and engineered treatment systems that are exposed to sunlight can be inactivated by a complex set of interacting mechanisms. The net impact of sunlight depends on the solar spectral irradiance, the susceptibility of the specific microorganism to each mechanism, and the water quality; inactivation rates can vary by orders of magnitude depending on the organism and environmental conditions. Natural organic matter (NOM) has a large influence, as it can attenuate radiation and thus decrease inactivation by endogenous mechanisms. Simultaneously NOM sensitizes the formation of reactive intermediates that can damage microorganisms via exogenous mechanisms. To accurately predict inactivation and design engineered systems that enhance solar inactivation, it is necessary to model these processes, although some details are not yet sufficiently well understood. In this critical review, we summarize the photo-physics, -chemistry, and -biology that underpin sunlight-mediated inactivation, as well as the targets of damage and cellular responses to sunlight exposure. Viruses that are not susceptible to exogenous inactivation are only inactivated if UVB wavelengths (280-320 nm) are present, such as in very clear, open waters or in containers that are transparent to UVB. Bacteria are susceptible to slightly longer wavelengths. Some viruses and bacteria (especially Gram-positive) are susceptible to exogenous inactivation, which can be initiated by visible as well as UV wavelengths. We review approaches to model sunlight-mediated inactivation and illustrate how the environmental conditions can dramatically shift the inactivation rate of organisms. The implications of this mechanistic understanding of solar inactivation are discussed for a range of applications, including recreational water quality, natural treatment systems, solar disinfection of drinking water (SODIS), and enhanced inactivation via the use of sensitizers and photocatalysts. Finally, priorities for future research are identified that will further our understanding of the key role that sunlight disinfection plays in natural systems and the potential to enhance this process in engineered systems.

This study explores how adding environmental perspectives to a developmental chemistry course affected student learning of both general chemistry and environmental chemistry concepts. In addition to measuring learning changes, changes in students' environmental attitudes and behaviors were also measured. A pretest-posttest design measured achievement in two sections of the same course for statistical comparison. The comparison section used everyday chemistry examples, such as pH of household substances and the thermodynamics of beverage coolers. The treatment section drew everyday examples from the environment, such as the pH of acid rain from different places and how burning fossil fuels releases carbon dioxide. Students in both sections showed concern for the environment from the beginning of the course, which did not change significantly during the semester. Assessments of general chemistry knowledge did show small yet significant differences between the two sections. Environmental chemistry assessments showed no significant differences between the two sections. The authors conclude that the amount of emphasis on environmental examples may not have been sufficient; they recommend further research on this topic using additional environmental examples taught more strategically throughout the course. (Contains 3 tables.)

The characterization of Co-C bonding and reductive Co-C cleavage in cobalt dichlorovinyl complexes is presented. The analysis of the Co-C cleavage following reduction has supported the direct formation of the cis-1,2-dichlorovinyl anion and not the cis-1,2-dichlorovinyl radical.

The synthesis, structures and reactivity of tetraphenylporphyrin (TPP) cobalt halovinyl complexes are described. The mechanism of halide substitution for the beta-halovinyl complexes is examined with kinetic experiments that showed a dissociative mechanism and supported the intermediacy of a cobalt acetylene complex.

A set of highly selective chemiluminescent probes has been developed for the detection and quantitation of singlet oxygen ([sup.1][O.sub.2]), a reactive oxygen species that is known to transform organic pollutants in the aquatic environment and elicits cytotoxic effects in biological systems. In this study, a trap-and-trigger detection method is employed, based on the reaction of [sup.1][O.sub.2] with a spiroadamantyl-substituted vinyl ether probe to form the corresponding thermally stable dioxetane, which undergoes chemiluminescent decomposition upon addition of a chemical trigger. The detection method is highly selective for [sup.1][O.sub.2] relative to superoxide anion and hydrogen peroxide. The sensitivity of this method allows for the accurate measurement of environmentally relevant (picomolar) steady-state [sup.1][O.sub.2] concentrations in relatively short exposure times. The detection method was used to detect and quantify [sup.1][O.sub.2] production in the reaction of dibenzoyl peroxide with superoxide anion.