Hydroxyl radical HO plays a central role in controlling chemical processes in the troposphere. Current mechanisms are believed to accurately describe its formation, destruction and interaction with other atmospheric trace gases in clean air. Hydroperoxyl radical H0₂ is Iinked to HO in several chain processes and serves among other roles as a reservoir for HO. The relative concentration (H0₂/HO) in clean air is believed to be the order of 10². We here examine the conditions under which steady-state kinetics apply to HO₁ chemistry and derive simple relationships which can be used to predict HO and H0₂ concentration from measurable concentrations of the more stable trace gases. The equations assume a simple form for conditions where the ambient nitrogen oxide concentration is less than 1 ppb. These equations allow closed-form evaluation of the sensitivity of [HO] and [H0₂] to changes in the concentrations of the controlling species and allow assignment of uncertainty limits to the predictions of current tropospheric chemical models. Although most current efforts to test fast tropospheric photochemistry center upon measurements of ambient [HO], our equations indicate that tropospheric [H0₂] determinations may provide a more direct and accurate initial test of our knowledge of HO₁ chemistry in the unpolluted lower atmosphere. Overall the goal of this study is to benefit the experimenter by providing the information of insight and simple but reliable equations and to understand the conditions under which these measurements should be made and how best to interpret their results.

published_or_final_version / Zoology / Master / Master of Philosophy

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

Thesis (Ph.D.)--Michigan State University. Environmental Engineering, 2008. / Title from PDF t.p. (viewed on Mar. 30, 2009) Includes bibliographical references. Also issued in print.

Thesis (M. Phil.)--University of Hong Kong, 1998. / Cover title. Includes bibliographical references (leaves 169-192).

Thesis (Doctoral)--Rijksuniversiteit Groningen, 2004. / Includes bibliographical references (p. [145]-151).

The syntheses of siloxyl and hydroxyl chain end functionalized polystyrene and poly(methyl methacrylate) by Atom Transfer Radical Polymerization (ATRP) were effected by the following methods: (a) α-Siloxyl functionalized polymers were prepared in quantitative yields via a one-pot ATRP synthesis method for the polymerization of styrene or methyl methacrylate using a new siloxyl functionalized initiator adduct, formed in situ by the reaction of (1-bromoethyl)benzene with 1-(4-t-butyldimethylsiloxyphenyl)-1- phenylethylene in the presence of CuBr/bpy or CuBr/PMDETA as catalysts in diphenyl ether at 90 -110 oC. The polymerizations proceeded via controlled living radical polymerization methods and α-siloxyl functionalized polymers with predictable number average molecular weights (Mn = 1.8 x 103 - 17.40 x 103 g/mol), narrow molecular weight distributions (Mw /Mn = 1.03 - 1.41) and regiospecificity of the functional groups were obtained in quantitative yields. Similarly, the one-pot ATRP synthesis method for the preparation of α-bis(siloxyl) functionalized polymers were effected by the initiation of styrene or methyl methacrylate polymerization with a new bis(siloxyl) functionalized initiator adduct, formed by the in situ reaction of 1,1-bis(4-t-butyldimethylsiloxylphenyl)- ethylene with (1-bromoethyl)benzene in the presence of CuBr/bpy or CuBr/ PMDETA as catalytic systems in diphenyl ether at 90 -110 oC. Each polymerization reaction proceeded via a controlled living fashion to afford quantitative yields of the corresponding α-bis(siloxyl) functionalized polymers with predictable number average molecular weights (Mn = 1.7 X 103 - 15.00 x 103 g/mol), narrow molecular weight distributions (Mw /Mn = 1.03 - 1.35) and good control of chain end functionality. The acid catalyzed hydrolysis of α-siloxyl and α-bis(siloxyl) chain end functionalized polymers afforded the corresponding α-hydroxyl and α-bis(hydroxyl) chain end functionalized polymers, respectively. Polymerization kinetic data was employed to determine the controlled/living character of each ATRP reaction leading to the formation of different siloxyl functionalized chain end functionalized polymers. Polymerization kinetic measurements show that the polymerization follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases with percentage monomer conversion, resulting in the formation of polymers with narrow molecular weight distributions. Thin layer chromatography (TLC), 1H and 13C Nuclear Magnetic Resonance Spectrometry (NMR), Fourier Transform Infrared Spectroscopy (FTIR), Size Exclusion Chromatography (SEC), Gas Chromatography (GC) and non - aqueous titrations were used to determine the structures and purity of the siloxyl functionalized initiator precursors as well as the siloxyl and hydroxyl functionalized polymers.

Galactitol and cis,cis,cis-1,3,5-cyclohexanetriol are polyols that are ideal examples of model compounds for ligands with lanthanide ions as they have their hydroxyl groups in favourable steric arrangement. Several complexes were synthesised with both lanthanide chloride and lanthanide nitrate salts with galactitol, and a variety of structures, both polymeric and monomeric, were observed. In all these complexes, galactitol acted as a bridging molecule between the lanthanide ions. A notable difference was the lanthanum chloride–galactitol complex that showed both chloride and galactitol bridging. The lanthanide nitrate salts formed only polymeric complexes with galactitol. Not all of the complexes showed nitrate ions coordinated to the metal centre, and in the neodymium nitrate– galactitol complex, which shows both monodentate and bidentate coordination of the nitrate groups. The coordination of the nitrate ions was confirmed using both XRD and IR analysis. Two complexes with lanthanide chloride salts and cis,cis,cis-1,3,5-cyclohexanetriol were synthesised and analysed. Lanthanum chloride formed a polymeric complex, which showed extensive chloride bridging between the metal centres. Praseodymium chloride formed a dimeric complex. All complexes were analysed with single-crystal X-ray diffraction, 1H NMR, 13C NMR and IR spectroscopy.

Laser Induced Fluorescence (LIF) is one of the chief methods for detecting ambient hydroxyl radicals. To measure the absolute concentration of this important atmospheric chemical species, accurately known quenching rate constants due to the dominant gases in the air are of paramount importance. Unfortunately, these rate constants have only been measured under conditions remote from those of ambient air. This dissertation reports the measurement of the rate constants of water, argon, nitrogen and oxygen under ambient conditions. As the LIF is carried out at atmospheric pressure, the OH fluorescence life-time becomes extremely short (about 1 ns). Time Correlated Photon Counting was used to study this short fluorescence phenomenon. The unique feature this study was that the deactivation processes of the excited OH could be described completely by a kinetic model. Detailed theoretical treatments of the LIF processes are presented. The data obtained are consistent with the accepted model, thereby demonstrating the usefulness and validity of the experimental approach. The rate constants (cc molecule('-1) sec('-1)) for quenching by water and argon were accurately measured. The vibrational relaxation rate constant by water (3.4 (+OR-) 0.6 x 10('-10)) is the first value ever reported, while the electronic quenching rate constants for water (k(,Q0) = 7.9 (+OR-) 0.47 x 10('-10), k(,Q1) = 1.48 (+OR-) 0.74 x 10('-10)) are the first measured at atmospheric pressure. The electronic quenching rate constants of the ('2)(SIGMA)(v' = 1) state (k(,Q1)) and the ('2)(SIGMA)(v' = 0) state (k(,Q0)) by argon are k(,Q0) = 0.48 (+OR-) 0.14 x 10('-12) and k(,Q1) = 0.24 (+OR-) 0.06 x 10('-11). The vibrational relaxation rate constant by argon is k(,10) = 0.34 (+OR-) 0.06 x 10('-11). The rate constants for oxygen (k(,Q1) (+OR-) k(,10) = 1.83 (+OR-) 0.43 x 10('-9) and k(,Q0) = 2.6 (+OR-) 0.6 x 10('-10)) are significantly higher than the limited measurements available at low pressure. The rate constants for nitrogen are k(,Q0) = 0.71 (+OR-) 0.08 x 10('-11) and k(,10) = 8.07 (+OR-) 0.65 x 10('-11). All these values are the first obtained at atmospheric pressure and although shown to be consistent with the widely scattered low pressure values, they allow more reliable analysis of ambient OH measurements, and result in a 31.2% increase in the published values.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / Inclusion compounds of two hydroxyl hosts with a variety of guests have been investigated. These host compounds are bulky molecules and have the ability to interact with smaller organic guests to form new compounds. The host 9-(1-naphthyl)-9H-xanthen-9-ol (H1), forms inclusion compounds with pyridine (PYR), N,N-dimethylacetamide (DMA), morpholine (MORP) and N-methyl-2-pyrrolidinone (NMP). The crystal structures of H1•NMP, H1•DMA and H1•MORP1 were successfully solved in the triclinic space group PĪ, whereas the inclusion compound H1•PYR crystallised in the monoclinic space group P21/c. A different inclusion compound involving morpholine, H1•MORP2 resulted from dissolution of H1 in a 1:1 molar ratio of MORP: DMA. H1•MORP2 crystallised in the space group PĪ. All of the abovementioned inclusion compounds demonstrated a host: guest ratio of 1:1 except for H1•MORP1 (host: guest ratio = 1: ). H1 interacts with pyridine and morpholine guests via (Host)O-H•••N(Guest) hydrogen bonds and via (Host)OH•••O(Guest) hydrogen bonds with N-methyl-2-pyrrolidinone and N,N-dimethylacetamide.