A study of methods for determining the relative abundances of the chlorine isotopes, and the results of mass spectrometric analyses of several chlorine-containing substances. Small variations are shown to exist in nature between the relative abundances of the chlorine isotopes in halite samples from at least two different localities. Other studies involving chlorine isotopes and their possible fractionation are included. / Thesis / Master of Science (MSc)

Most of the literature concerning chlorine deals with continuous exposure, and is not readily applicable to this intermittent release of chlorine. Brungs(1973) reported that very little work has been done on the effects of intermittent exposure on fish, and that temperature has little or no effect on chlorine toxicity. Since many steam-electric generating plants are on streams with predominantly warmwater fish, it was important to determine the effects of the intermittent release of chlorine on a fish of this type. The toxicity of intermittent chlorination, and the possible interaction with temperature to a warmwater fish, bluegill (Lepomis macrochirus) was investigated with the support of the American Electric Power Corporation. Because relatively little is known about the physiological effects of intermittent chlorination on fish, a study of this problem was performed using the rainbow trout (Salmo irdneri).This species was chosen because of the availability of large mature specimens. the ease of handling- and the considerable amount of physiological background data in the literature. Another part of this study was to investigate the histological changes occurring in the bluegill and rainbow trout that resulted from intermittent chlorination. The data obtained were used to construct an hypothesis concerning the toxic mode of action of chlorine to freshwater fish. / Ph. D.

Numerous wastewater treatment processes are currently available for nitrogen removal or ammonia conversion to nitrate. Those that are economically feasible rely mostly on microbiological processes, which are only effective when the microorganisms remain in a healthy state. If a biological process upset was to occur, due to a toxic shock load or cold weather, it may result in a discharge of ammonia or total nitrogen into the receiving water body. The impact of such a discharge could have deleterious effects on aquatic life or human health. The main objective of the breakpoint pilot study was to define optimum breakpoint pilot plant operating conditions which could then be applied to the design of a full scale breakpoint facility and serve as an emergency backup to biological nitrification. A pilot study was built on site at the Upper Occoquan Sewage Authority's Regional Water Reclamation Facility in Centreville Virginia. Testing was conducted in two phases (I and II) over a two year period in order to determine the operating conditions at which the breakpoint reaction performed best. Tests were performed during Phase I to determine the optimum operating pH, Cl₂:NH₃-N dose ratio, S0₂:Cl₂ dose ratio, and the minimum detention time for completion of the breakpoint reaction. Other testing done during Phase I included several special studies; including examination of appropriate analytical methods for monitoring breakpoint reactions, and investigation of the breakpoint reaction by-product nitrogen trichloride. Phase II testing examined how varying breakpoint operating temperatures, varying influent ammonia concentrations, higher influent organic nitrogen concentrations, and higher influent nitrite concentrations influenced the performance of the breakpoint pilot operation. Averages of data from operation at three different rapid mix pHs (7.0, 7.5, and 8.0) showed that pilot performance (i.e., ammonia oxidation) improved and the reaction was more stable at the higher operating pHs 7.5 and 8.0. Examination of dose ratios used during the study showed that the ideal operating ratios for this particular water was around 8:1 Cl₂:NH₃-N for the breakpoint reaction and 1.3:1 S0₂:Cl₂ for the dechlorination reaction. Although detention times for completion of the breakpoint reaction varied with pilot influent temperature, it generally required around 30-35 minutes to reach ammonia concentrations of < 0.2 mg/L NH₃-N at 8-12°C. Completion of the breakpoint reaction was found to be quickest at 20°C (the highest water temperature tested at the pilot). The tests of varying influent ammonia concentrations showed that although higher influent ammonia concentrations (11.0 mg/L) resulted in faster ammonia oxidation rates initially, the pilot operated better and had the same final performance results when the influent ammonia was lowered. Increasing the organic nitrogen concentrations (~ 1.0 mg/L) in the pilot influent resulted in a slightly higher Cl₂:NH₃-N dose ratio needed to reach breakpoint, a higher S0₂:Cl₂ dose needed to dechlorinate, and resulted in the formation of numerous disinfection byproducts. Increasing the nitrite concentration in the pilot influent increased the chlorination dose requirement. / Master of Science

The development of an analytical method for the determination of total organic-bound chlorine (TOCl) produced during the chlorination of municipal wastewater effluents is presented. Sewage effluent from the Denton, Texas municipal treatment plant was chlorinated at high chlorine doses (1000 - 4000 ppm), as well as typical treatment levels. Chlororganics present in the wastewater, before and after chlorination, were concentrated by adsorption on Amberlite XAD-2 macroreticular resin, followed by elution with diethyl ether. After concentration, the extracts were analyzed for TOC1 by microcoulometry. Analysis of wastewater extracts revealed the production of substantial amounts of new chlorinated organics when effluents were treated with chlorine. The method shows good precision and estimated accuracy is favorable.

The results from this study show how different precursors affect halonitromethane (HNM) formation as well as how different free chlorine doses can affect HNM speciation. This study shows that the low pressure ultraviolet (LPUV) and free chlorine concurrent exposure can enhance HNM formation. In addition, most previous studies in the literature showed trichloronitromethane (TCNM) forming in greater quantities followed by monochloronitromethane (MCNM) and dichloronitromethane (DCNM). However, the results of this study show that, in deionized (DI) water matrices, MCNM forms in greater quantities at chlorine to nitrogen (Cl:N) ratios less than 3, while TCNM forms in greater quantities at Cl:N ratios greater than 3. Even so, the increase in TCNM formation did not increase linearly as the Cl:N ratio increased; there was a decreased rate of return when Cl:N ratios were greater than 3. The type of nitrogenous precursors can affect the amount of HNMs formed, with glycine forming a higher amount of total HNMs compared to methylamine (MA) and dimethylamine (DMA). The source of water can also affect which HNM species is formed in greater concentrations. The limited number of real water samples showed that the river waters have higher than normal total organic carbon (TOC) and dissolved organic nitrogen (DON), which are associated with greater nitrogenous precursors and higher HNM formation. Each water source can have different nitrogenous precursors; river waters may have more algal organic matter while wastewater would have higher organic matter and synthetic chemicals. In addition, source waters can have different constituents, such as varying dissolved oxygen (DO) levels and inorganic ions, which might inhibit HNM formation or affect specification.

Call number: LD2668 .T4 1986 B32 / Master of Science / Grain Science and Industry

Detailed photochemical modeling is used to guide air quality management activities around the world. These models use condensed chemical mechanisms to describe the multiphase processes that lead to chemical transformations in the atmosphere. Condensed mechanisms have generally not included the reactions of halogens, yet an expanding body of ambient observational evidence indicates that halogen chemistry, particularly chlorine chemistry, can be important in urban environments. This thesis is focused on the development, implementation, and evaluation of condensed chemical mechanisms that incorporate chlorine chemistry pathways. Gas phase reactions involving molecular chlorine and nitryl chloride (ClNO₂), as well as heterogeneous reactions involving particulate chloride species are addressed. The predictions of the modeling work presented here are compared to environmental chamber experiments and field observations. / text

No description available.

The gas phase reactions of atomic chlorine with hydrogen sulfide, ammonia, benzene, and ethylene are investigated using the laser flash photolysis / resonance fluorescence experimental technique. In addition, the kinetics of the reverse processes for the latter two elementary reactions are also studied experimentally. The absolute rate constants for these processes are measured over a wide range of conditions, and the results offer new accurate information about the reactivity and thermochemistry of these systems. The temperature dependences of these reactions are interpreted via the Arrhenius equation, which yields significantly negative activation energies for the reaction of the chlorine atom and hydrogen sulfide as well as for that between the phenyl radical and hydrogen chloride. Positive activation energies which are smaller than the overall endothermicity are measured for the reactions between atomic chlorine with ammonia and ethylene, which suggests that the reverse processes for these reactions also possess negative activation energies. The enthalpies of formation of the phenyl and &#946;-chlorovinyl are assessed via the third-law method. The stability and reactivity of each reaction system is further rationalized based on potential energy surfaces, computed with high-level ab initio quantum mechanical methods and refined through the inclusion of effects which arise from the special theory of relativity. Large amounts of spin-contamination are found to result in inaccurate computed thermochemistry for the phenyl and ethyl radicals. A reformulation of the computational approach to incorporate spin-restricted reference wavefunctions yields computed thermochemistry in good accord with experiment. The computed potential energy surfaces rationalize the observed negative temperature dependences in terms of a chemical activation mechanism, and the possibility that an energized adduct may contribute to product formation is investigated via RRKM theory.

Thesis advisor: Amir H. Hoveyda / Chapter 1. Development of Ru-Based Catechothiolate Complexes for Z-selective Ring-Opening/Cross-Metathesis and Cross-Metathesis. We have developed a broadly applicable Ru-catalyzed protocol for Z-selective ring-opening/cross-metathesis (ROCM). Transformations are promoted by 2.0–5.0 mol % of a Ru-based catechothiolate complex, furnishing products in up to 97 % yield and >98:2 Z:E ratio. The Z-selective ROCM processes are found to be compatible with terminal alkenes of different sizes that include the first examples involving heteroaryl olefins, 1,3-dienes, and O- and S-substituted alkenes as well as allylic and homoallylic alcohols. Reactions with an enantioenriched α-substituted allylic alcohol are shown to afford congested Z-olefins with high diastereoselectivity. The insights gained from these investigations provided the impetus to develop electronically modified Ru catechothiolate catalysts that are readily accessible from a commercially available dichloro-Ru carbene and an easily generated air-stable zinc catechothiolate. The new complex is effective in catalyzing Z-selective cross-metathesis (CM) of terminal alkenes and inexpensive Z-2-butene-1,4-diol to directly generate linear Z-allylic alcohols, including those that bear a hindered neighboring substituent or reactive functionalities such as a phenol, an aldehyde or a carboxylic acid. Transformations typically proceed with 5.0 mol % of the catalyst within 4–8 hours under ambient conditions, and products are obtained in up to 80% yield and 98:2 Z:E selectivity. Utility is highlighted through synthesis of a molecular fragment en route to anti-tumor agent neopeltolide and in a single-step stereoselective gram-scale conversion of renewable feedstock to synthetically valuable Z-allylic alcohols. Chapter 2. Kinetically Controlled Z- and E-Selective Cross-Metathesis to Access 1,2- Disubstituted Alkenyl Halides. We have discovered that previously unknown halo-substituted molybdenum alkylidenes are capable of participating in highly efficient olefin metathesis reactions that afford linear 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by 1.0–10.0 mol % of a Mo-based pentafluorophenylimido monoaryloxide pyrrolide (MAP) complex that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, delivering a myriad of alkenyl chlorides, bromides and fluorides in up to 91% yield and >98:2 Z:E ratio. Through mechanism-based modification of the aryloxide ligand, a newly synthesized Mo-based MAP complex was shown to be effective in promoting kinetically controlled E-selective CM to access the corresponding thermodynamically less favored E-isomers of alkenyl chlorides and fluorides. Reactions typically proceed within 4 hours at ambient temperature with 1.0–5.0 mol % of the catalyst, which may be utilized in the form of air- and moisture-stable paraffin pellets. Utility of the aforementioned protocols is demonstrated through preparation of biologically active compounds and related analogues as well as late-stage site- and stereoselective fluorination of complex organic molecules. Chapter 3. Molybdenum-Based Chloride Catalysts for Z-Selective Olefin Metathesis. A new class of Mo-based monoaryloxide chloride (MAC) complexes for Z-selective olefin metathesis has been developed. The MAC catalysts are capable of promoting CM with commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene to furnish the higher-energy Z-isomers of trifluoromethyl-substituted alkenes in up to 95% yield and >98:2 Z:E selectivity. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be accomplished with appreciably improved efficiency and Z-selectivity. The method enables synthesis of biologically active compounds and CF3-analogues of medicinally relevant molecules. Density functional theory (DFT) calculations shed light on the origins of the activity and selectivity levels observed in these transformations. Chapter 4. Stereoselective Synthesis of Z- and E-Trisubstituted Alkenes by Merging Cross-Coupling with Cross-Metathesis. We have discovered that challenging acyclic E- and Z-trisubstituted alkenes, particularly alkenyl chlorides and bromides, can be accessed efficiently and in high stereoisomeric purity (up to >98% E and 95% Z) through a sequence involving catalytic cross-coupling followed by stereoretentive CM promoted by Mo-based catalysts. Initial exploratory studies with 1,1-disubstiuted alkenes revealed crucial mechanistic features of the transformations that led us to utilize readily accessible trisubstituted olefins as substrates, in combination with commercially available 1,2-dihaloethenes as cross-partners for CM. Applications to synthesis of biologically active compounds and synthetic precursors underscore utility. The stereoretentive transformations may be extended to trisubstituted non-halogenated alkenes such as aliphatic olefins. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.