The growth of the layer formed on atomically clean lithium metal upon exposure to SO₂ gas is sequentially studied by controlling the quantity of gas reacted with the surface in a specially constructed vacuum system. A Fast Fourier Transform algorithm for the removal of instrumental broadening, and quantized and inelastic electron loss processes from the background of an Auger spectrum is presented. The deconvolved peaks for the S(LMM) and O(KKL) valence transitions are used to determine the molecular composition of the layer at each stage of its formation. The associated peak areas give the quantity of SO₂ reacted with the surface and the relative amounts of sulfur and oxygen present in each layer. The results indicate that two distinct layers of different composition are formed. The lower layer is a complete monolayer of Li₂O/Li₂S in a two-to-one ratio. The upper layer is thicker and consists of LiS₂O₄ and LiS₂O₃ in a 50% mixture. The formation of the upper layer is observed only after exposures of the surface to partial pressures of SO₂ greater than one millitorr. A model to explain the formation of the two layers and the observed pressure dependence is given. A flow method is used to study the kinetics of the Li-SO₂ reaction at submonolayer coverages. The pressure in a reaction vessel is monitored as a function of time when a fresh Li surface is exposed. A reaction order between 0.5 and 0.9 results, indicating that the surface of the scraped Li is energetically heterogeneous with respect to sites available for adsorption. An Arrhenius plot of the data indicates that the activation energy for the dissociative chemisorption to form the first monolayer lies between 2 and 5 kcal/mole. The sources for site heterogeneity and the activation energy are discussed. The resulting molecular model is used in combination with preliminary electrochemical results to compare the gas phase layer with the film formed on Li anodes in the Li/SO₂ ambient temperature battery. The model proves to be useful in explaining storage and discharge characteristics of the battery that are due to the presence of the anodic film.

The regioselectivity of the reaction of hydroxyl radical addition to toluene and naphthalene are examined in this study over the temperature range of 25°C-45°C. Also, the relative rates of reactivity as compared to benzene are determined for toluene, naphthalene, mesitylene, and p-xylene over the same temperature range. 2-(t-Butylazo)prop-2-yl hydroperoxide was used as the hydroxyl radical source and 1,1,3,3-tetramethylisoindolin-2-yloxyl was used as radical trap. For toluene the relative rates of addition were found to be 4 times greater for the ortho position versus the meta postion and 2 times greater for the para position versus the meta position, when the number of meta and para sites are taken into account. / Department of Chemistry

No description available.

No description available.

Hydroxyl Radical (HO·) is a highly reactive radical species which is an important member of a class of chemical species known as Reactive Oxygen Species (ROS). Hydroxyl radical typically has an extremely short lifetime under most conditions and its highly reactive nature makes it hard to detect by conventional methods used for study of free radical kinetics. In this study we propose and develop an alternative method for relative reactivities and regioselectivities of hydroxyl radical reactions with aromatic compounds in organic solvents. Hydroxyl radical is generated by the thermolysis of a tert-butyl azohydroperoxide which dissociates to yield hydroxyl and tert-butyl radicals, nitrogen, and acetone. TMIO is used to trap the tert-butyl radical, but is less likely to trap hydroxyl radical, which is free to react with the target arene to yield a hydroxycyclohexadienyl species. These species undergo hydrogen abstraction with TMIO to yield phenols, which may be derivatized with an appropriate silylating agent (in this case BTFSA), and analyzed using gas chromatography with detection by flame ionization (GC-FID) and mass spectrometry (GC-MS). The reactivity and selectivity of reaction of hydroxyl radical with various aromatic compounds is determined at different temperatures to obtain relative reaction rates. In this work, the reactivities and selectivities for HO• reactions with simple arenes, such as toluene and naphthalene are investigated. / Department of Chemistry

The structure and solvation of ions are studied from different aspects using various kinetic, spectroscopic and thermodynamic techniques. The solvation of a wide range of ions, both simple and complex, is investigated by calculation of sets of single-ion transfer chemical potentials for a series of binary aqueous solvent mixtures. Observed trends are discussed in terms of the effects on ion solvation of solute and solvent structure and solute-solvent interactions. Structure, solvation and also reactivity of sane low- spin iron (II) di-imine complexes containing unsymmetrical Schiff base ligands are investigated using a variety of techniques. The occurrence of diastereoisomerism in complexes of this type is probed using complementary techniques which highlight different aspects of this phenomenon. Thus, the differing reactivities of, and the differing spatial orientations in, possible diastereoisomeric forms are utilized in detecting diastereoisomers by kinetic and 1H nmr spectroscopic methods respectively. In addition, for complexes of this type, links between structure, solvation and reactivity are investigated using kinetic data, solubility data, ultraviolet/visible absorption spectra and 1H nmr spectra obtained for the complex species.

No description available.

The work described in this thesis is concerned with the study of extending known crystal engineering principles to the influence of anions on crystal packing and reactivity. Some features arising from this study include: single-crystal to single-crystal reactivity; an important role of water in modifying the course of the reaction; the movement of water associated with the reacting pair of acridizinium cations during the photodimerization process; possible martensitic phase transition from the acridizinium bromide monohydrate P2<SUB>1</SUB>/a isomer to P1 isomer; phase transformations accompanying dimerization; the generation of crystalline solutions incorporating two or more anions and the modification of structure as a function of anion with consequential differences in reactivity. Results from both theoretical approach and experimental studies on acridizinium and 9-methylacridizinium salts suggest that ionic molecules pack preferrentially in a centrosymmetric manner favoured by both the geometrical close-packing model and Coulombic energy. Crystal morphologies are modified by varying anions. The morphological changes can be correlated consistently with the size and shape of the anion, and the electronic property of the anion also contributes to this change (e.g. the formation of hydrogen bond). Molecular packing arrangements (structural relationship) of these compounds can also be correlated consistently with the size, shape and the electronic properties of the anions. There is a good correlation between the photoreactivity and the crystal structure. The relative conversion rate, assuming that the excimer formation is the rate determining step, can be predicted reasonably well from the ground state structure of the monomer pair. A possible mechanism for the photodimerization of acridizinium and 9-methylacridizinium salts was proposed based on the results from the electrochemical, spectroscopic and electron resonance studies.

This research has been directed at the study of organosulfur frontier orbital interactions with transition metal d-orbitals. Two novel thioether complexes tricarbonyl(1,4,7-trithiacyclononane)molybdenum(O) and tricarbonyl(2,5,8-trithianonane)molybdenum(O), have been prepared and structurally characterized by single crystal x-ray crystallography. The facial configuration of the carbonyl ligands provides a unique point of reference for describing the two polythioether ligands in terms of the free ligand's frontier orbitals. The relative carbonyl stretching frequencies of the two metal complexes indicate that 1,4,7-trithiacyclononane is a poorer donor than 2,5,8-trithianonane. This result is explained in terms of mechanical constraints placed on the mesocyclic polythioether which are absent in its acyclic analogue. The coordinatively unsaturated species (n⁵-C₅H₅)MO(NO)(SC₆H₅)₂ has been characterized by x-ray crystallography and its electronic structure has been modeled using Fenske-Hall molecular orbital calculations. The monomeric nature and chemical inertness of (n⁵-C₅H₅)MO(NO)(SC₆H₅)₂ are attributed to dπ-pπ bonding between the thiolate ligands and an empty molybdenum dπ orbital. The dπ-pπ interaction simultaneously strengthens the metal thiolate bond and makes the complex less susceptible to nucleophilic attack by raising the energy of the LUMO. The rotational orientations of the thiolate ligands observed in the solid state support this electronic model. For (n⁵-C₅H₅)Fe(CO)₂SR, the dπ-pπI antibonding interaction between the thiolate ligand and the metal has been modeled using Fenske-Hall molecular orbital calculations and experimentally investigated by photoelectron spectroscopy. The calculations predict that the HOMO is metal-sulfurn-antibonding and largely sulfur 3p in character. The observed HOMO ionization energies of (n⁵-C₅H₅)Fe(CO)₂SC₆H₄-p-Z; Z = OMe, H, Cl, CF₃, N0₂; correlate with several chemical properties including the rate of electrophilic attack on the sulfur by alkyl halides to give the thioether complex [(n⁵-C₅H₅)Fe(CO)₂(SR₂)]X and by electron-deficient alkynes to give the heterometallacycle (n⁵-C₅H₅)(CO)FeS(R)-C=C=C=0. The latter reaction is compared to the similar reaction of alkenes and alkynes with (n⁵-C₅H₅)Fe(CO)₂PR₂ to give (n⁵-C₅H₅)(CO)FeP(R)₂-C=C-C=0. X-ray crystal structures of one of the sulfur-containing and one of the phosphorus-containing heterometallacycles have been obtained.

The dissolution of copper metal in the presence of copper(II) ions and allyl alcohol in aqueous solution is found to be pseudo-first order with respect to both copper(II) ions and allyl alcohol. The reaction is inhibited by acid. The rate determining step is not the formation of copper(I) but the transfer of electrons from the surface of copper metal to the copper(II) ions in solution. The reaction rate has been monitored spectrophotometrically by complexing the copper(I) formed with 2,9-dimethylphenanthroline (neocuproin) and measuring the absorbance of the solution at the wavelength of maximum absorption of the complex, 450 nm. Other factors that affect the reaction are the presence of anions, the solvent composition, the nature of the unsaturated ligand used to stabilize the copper(I) and the rate of stirring. The reduction of copper(II)-neocuproin by allylamine and allyl alcohol has been studied in basic solution. A method has been developed for the rapid, sensitive determination of CN⁻ based on a spectrophotometric technique using copper(I)-neocuproin as a reagent. SCN⁻ does not interfere but S²⁻ appears to be a very powerful source of interference. By appropriate choice of the concentration of copper(I)-neocuproin reagent the range of response can be adjusted to be in the range 1-10 ppm. The theoretical detection limit of the method is as low as 19 ppb at the 95% confidence limit and the precision, measured as the relative standard deviation, is better than 1.5%. The disturbance of the equilibrium between the bis ligand and mono ligand complexes of copper(I) appears to be the reason for the observed decrease in absorbance on the addition of cyanide to a solution of copper(II)-neocuproin. The problems associated with using the commercially available ion selective electrode for cupric determination have been highlighted. The possibility of developing a PVC matrix membrane electrode for the determination of CN⁻ has been explored. The main difficulty is the instability of the copper(I)-neocuproin complex at pH values as high as 11 that are required to stabilize CN⁻.