The rhodium speciation in nitric acid has been identified, primarily by the use of 103Rh Nuclear Magnetic Resonance Spectroscopy. The results have indicated that the rhodium species in stored high level waste (HLW) will range from the hexaaquo ion, {Rh(H20)6}3+-to complexes of the general formula {Rh(H20)6-n(NO2)nl(3-n)+, depending on the nitrite ion concentration. The solvent extraction of these complexes by dinonylnaphthalene sulphonic acid and various organo-phosphine sulphides has been investigated, and an integrated scheme for recovering rhodium from HLW is proposed.

14 MeV neutron activation analysis, based on the 82Se(n,2n) Se81m nuclear reaction, has been investigated for the measurement of selenium in environmental waters. The levels of the selenium present in environmental waters and the relatively high limit of detection achievable with fast neutron activation analysis resulted in the need to develop a concentration procedure for the extraction of selenium from large volumes of environmental water before neutron activation.

Tritium labelled compounds are widely used in the physical and life sciences. The preparation of such compounds is a very important area of chemistry. Although the methods are, on the whole, fairly simple and straightforward, there is still a need for improvement. The same applies as far as the analysis of the tritium distribution is concerned. High resolution 3H NMR spectroscopy of solutions is now a well established technique. However many compounds exist as solids which are either insoluble or sparingly soluble in organic solvents, consequently there is a need to develop high resolution 3H NMR spectroscopy of solids. The thesis therefore consists of four chapters. The first is a review dealing with the properties of tritium, the various labelling methods and tritium nuclear magnetic resonance spectroscopy. In the second chapter an account is given of the way in which complex metal tritides and tritiated methyl iodide, an important reagent which enables one to introduce three tritium atoms in a single step and therefore obtain products of very high specific activity, are prepared. In the third chapter an account is given of the synthesis and attempted tritiation of two potential 5-HT re-uptake inhibitors, prior to their use in biological studies. Whilst the synthesis of the two compounds N-[[[l-[(l-bromo-2-naphthalenyl)methyl]-4-piperidinyl]amino]carbonyl]-3-pyridinecarboxamide, and N-[[[l-[(l-bromo-6-fluoro-2-naphthalenyl)methyl] -4-piperidinyl]amino]carbonyl]-3-pyridinecarboxamide, was successful the tritiation procedure led to unforseen difficulties. Finally in the fourth chapter solid state tritium NMR spectroscopy, using a magic angle accessory, was developed and used in the analysis of several tritiated compounds.

A beta spectrometer, consisting of a liquid scintillation counter, coupled to a programmable multichannel analyser was used to achieve the objective of detecting and measuring beta activity in low level aqueous environmental solution as well as identifying the radioisotopes present. Aqueous solutions of standard beta emitters, covering a range of energies between 18.6 KeV and 3550 KeV, were used to develop computer methods for analysis. The best proportions of the counting cocktail was found consist of 4.0 ml of aqueous sample, 3.0 ml of Triton X-100 and 3.0 ml of toluene containing 4.0 g per litre PRO and 0.4 g per litre POPOP. The effects of pH, acids, bases, buffers, and salts on the stability of the mixture and on the detection efficiency of the radioisotopes, were investigated and found not to be severe. Pretreatment of the sample was not required. It was found that temperature changes, beyond the operating temperature range, could result severe errors. 1024 channels of aquisition area, for the collection of the spectra, give good conditions for computer analysis. End channel and channel number of maximum count calibration gave a linear relationship to the Em, of standard beta emitters. It was found that the theoretical fitting of the spectra is possible and the normalisation ratio V of the theoretical to the experimental fitting procedure has alinear relationship to the activity of emitter. Kurie plot was applied for checking the Emav value of the emitters used. Application of the Cerenkov counting technique for beta emitters, gives extra data to support the main results. For the analysis of environmental solutions, which may contain a variety of radioisotopes, the system was used to obtain spectra of alpha emitters, beta emitters with internal conversion and Cerenkov radiation. Synthetic mixtures of tritium and carbon-14 of activity ratios between 8:1 and 1:8 were used to investigate the problems of multielement spectral analysis.

Glassy methanolic and ethanolic solutions of molecular oxygen were exposed to X-rays at 4.2 K. A marked inhibition of the formation of e-t centres together with formation of O2- was observed. The results suggest that the environment of O2 in methanol is such that initial hydrogen-bond transfer to O2- is facile even at 4.2 K. In ethanol, O2- is too far from hydrogen bonded OH groups for this mechanism to operate. Dilute aqueous glassy solutions of the enzyme superoxide dismutase (SOD) were exposed to ?-radiation. Reduction of the native Cu(II) centre to Cu(I) was observed. A reaction was established between this reduced form and O2-. Potassium hexacyanoferrate II was shown to be a suitable chemical reducing agent for SOD after purification, whereas sodium dithionite was shown to modify the copper centre. Study of the disulphide bridge of reduced SCD revealed RSSR- radicals and, in sane cases, species 'X', depending on the nature of the reducing agent. The pH dependence of S(X) and the effect of some anions has been illustrated and serves to confirm documented results. Dilute aqueous glassy solutions of powered haemoglobin and diluted sarrples of whole blood were exposed to ?-radiation. ? and ? subunit haem Fe-O2 centres were identified at 77 K and several spectral changes recorded during warming. Tentative identification of these species has been made.

Despite their discovery during the 1940's, there are still many unanswered questions surrounding the elements past uranium, or transuranic elements. In the recent years more evidence is emerging that suggest the bonding and structure of the actinides in more complex than previous thought. We look to expand on this by judicious choice of ligands as a means of probing the bonding observed in actinide complexes. Towards the exploration of the nature of bonding in the actinide, the development of trends for ligand interaction is a goal. Currently, there is very little to indicate which ligands will show more covalent interactions or which will show more ionic interactions. Examining ligand systems that demonstrate a variety of characteristics, various oxoanions have been chosen over the traditional carbon based ligands. It is reasonable to view f-element interactions with oxoanions as metal ligand interactions and an excellent system to study displaying a variety of characteristics. Currently the overall softness and polarizablity of ligands is the only characteristic that lends some insight to the potential for covalency. However the choice of oxoanions makes the application of polarizablity a guide difficult. Through use of the quantified hyperpolarizability of oxoanions a guide to discriminate between anions with lower polarizablity such as phosphite and those with higher polarizablity such as molybdate. With the higher degree of polarizablity indicated by the hyperpolarizability, more covalent bonds with actinide metals are expected leading to unusual properties and differences when compared with lanthanide. Though traditional mild hydrothermal methods have proved suitable for the synthesis of crystalline products, there are limits to the method. To expand the synthetic versatility of the lab and access new hydrothermal phase space autoclaves for synthesis in supercritical media were developed. In particular supercritical water is a desirable synthetic media for crystal growth owing to characteristics as a solvent and the ability to access oxidations of metals otherwise inaccessible to mild hydrothermal methods. This dissertation is focused on the development of synthetics methods for the isolation and characterization of new f-element materials. To this end, each chapter reports on the synthetic methods and the novel f-element materials that incorporate highly polarizable oxoanions. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2015. / April 9, 2015. / Includes bibliographical references. / Thomas Albrecht-Schmitt, Professor Directing Dissertation; Ingo Wiedenhöver, University Representative; Susan Latturner, Committee Member; Albert Stiegman, Committee Member.

<p> Fusion in neutron-rich environments is presently a topic of considerable interest. For example, the optical emission spectrum from the neutron star merger GRB170817A clearly establishes this neutron-rich environment as an important nucleosynthetic site. Fusion of neutron-rich light nuclei in the outer crust of an accreting neutron star has also been proposed as responsible for triggering X-ray super-bursts. The underlying hypothesis in this proposition is that the fusion of neutron-rich nuclei is enhanced as compared to stable nuclei. A good approach to understand how fusion proceeds in neutron-rich nuclei is to measure the fusion excitation function for an isotopic chain of nuclei. Modern radioactive beam facilities provide the opportunity to systematically address this question. An experimental program has been established to measure the fusion excitation function for light and mid-mass neutron-rich nuclei using low-intensity radioactive beams. The technique was initially demonstrated by measuring the fusion excitation functions for <i>18</i>O and ¹⁹O nuclei incident on a ¹²C target. The beam of ¹⁹O ions was produced by the <i>18</i>O(d,p) reaction with an intensity of 2-4 x 10⁴ p/s at Florida State University. Evaporation residues resulting from the de-excitation of the fusion product were distinguished by measuring their energy and time-of-flight. To explore mid-mass neutron-rich nuclei much further from stability, the fusion excitation functions for ^39,47K + ²⁸Si were measured using the ReA3 reaccelerator facility at the National Superconducting Cyclotron Laboratory at Michigan State University. Incident ions were identified on a particle-by-particle basis by &Delta;E-TOF just upstream of the target. Fusion products were directly measured and identified by the E-TOF technique with an efficiency of ~70%. The measured fusion excitation functions for both the light and mid-mass systems have been compared to various theoretical models to elucidate how structure and dynamics impact the fusion of neutron-rich nuclei.</p><p>

In the present thesis, the effects of the carbonate radical anion on lignin and cellulose were investigated. The carbonate radical has a rather high reactivity towards aromatic lignin constituents. It reacts especially fast with phenolates. All these reactions occur by way of electron transfer. Small carbohydrates react with CO3 •- much slower than aromatics. These reactions are hydrogen transfer reactions. However, in very basic media, where the carbohydrates deprotonate to some extent, their anions react with CO3 •- by way of electron transfer and the rates approach those of non-phenolic aromatics. These findings suggest that in neutral or slightly alkaline media CO3 •- might serve as an excellent delignifying agent of pulp down to very low lignin contents. With small carbohydrates possessing one or two glucosidic bonds, CO3 •- abstracts hydrogen predominantly from C1 – H bonds, which results in rupture of the glucosidic linkage. Interestingly, however, the glucosidic bonds in cotton linters are rather resistent towards CO3 •-. This has probably morphological reasons. These results imply that, even at very low lignin contents, where CO3 •- is bound to react with cellulose, the reactions will not lead to substantial decrease in pulp viscosity. At present the cheapest and most practical way of producing CO3 •- radicals in the presence of pulp is to mix the latter with peroxynitrite and CO2. We have performed such experiments on pulp with very promising results. The Kappa number decreased substantially, brightness increased, while the viscosity remained high. This confirms the predicted excellent properties of the carbonate radical. However, before the peroxynitrite method can be implemented in the pulp industry, a number of technical problems has to be solved. Chief among them is a slow and steady dosage of peroxynitrite to minimise side reactions of the radicals with peroxynitrite and the nitrite impurity. The fate of the •NO2 radical, the coproduct of CO3 •-, has also to be assessed. •NO2 will probably have to be removed by vigorous degassing in order to block the possible nitration of cellulose. / QC 20101001

Thesis (M.Sc. (Biochemistry))--Mahidol University, 1983.

The periodic table of the elements, derived from numerous attempts in the 1800s to systematically examine the chemistry found in nature, has seen a stark evolution over the last century. The elements of the actinide series are the frontier of a radical discontinuity in periodicity, driven by a relativistic reorganization of the frontier orbitals. Characterization of the chemistry of these elements with simple model species enables detailed coordination between structural chemistry and theoretical characterization. Such examinations advance understanding of these relativistic shifts. With the ever-growing influence of these effects, periodic trends on the table the elements break down, and synthetic elements beyond uranium offer new opportunities to probe these divergent and nonlinear chemistries. The introductory chapter addresses the history of the synthesis and the initial chemical characterization of the transuranium elements, with a brief basic introduction given to discuss the reaction physics which will follow. These elements share a single common feature in that they all have large Z values, and thus have electronic structures that are significantly altered by both scalar relativistic effects and spin-orbit coupling. These effects scale nonlinearly with increasing Z and create unexpected deviations both across series and down groups of elements. The magnitude of these effects is large enough that orbital energies rearrange and mix in ways that complicate incomplete depictions that are based solely on electron repulsion. The second chapter discusses calculations with nuclear reaction codes to examine a potential production rate improvement that may be derived by super-heavy synthesis with reactions run in inverse kinematics. This result is particularly important for continuing the evolution of the periodic table, as increased production rates enable new spectroscopic analyses of electronic and nuclear structure that can, in future years, potentially rewrite our understanding of relativity at the most extreme scale heretofore produced. The third chapter discusses new structural, spectroscopic, and theoretical features of uranium fluorides that are relevant for fundamental uranium(IV) chemistry and actinide fluoride reactors. The simple system of tetraammonium octafluorouranate is employed to derive fundamental understanding of the uranium-fluorine interaction. The structure is composed of isolated molecules, enabling a clear look at the U4+ (f 2) species in the most ionic bonding environment possible, without the possibility of direct interactions or strong interactions through ligands between uranium centers. Characterization of single-crystals by x-ray diffraction, absorption spectroscopy, and magnetic analysis up to 45 T is interwoven with extensive theoretical treatment by CASSCF. The influence of different active spaces and representations of the structure is examined in the context of the experimental evidence. The Interacting Quantum Atoms method is used to examine the nature of the U-F bond, concluding that there is a non-negligible degree of covalent character (9% of the total bond energy) even with the most ionic simple anion of fluoride. Two new sodium uranium(IV) pentafluorides were synthesized from uranium dioxide, HF, and NaF under mild hydrothermal conditions. Although β-NaUF5·H2O crystallizes in the (lower) monoclinic crystal class, it possesses greater crystal lattice energy than the previously-known orthorhombic α-NaUF5·H2O. Trigonal β-NaUF5 possess significantly different bonding between [UF9]5- moieties than the α-phase, with higher symmetry and greater lattice energy than its orthorhombic structural isomer, which is most directly comparable in structure to Na3,4M2+/3+U6F30. Single-crystal absorption spectra of these compounds are reported and correlated. Simulated powder x-ray diffraction data are also reported and compared to address a (mis)identification of the NaUF5 series that dates back to the Manhattan Project. The final textual chapter extends the methods discussed in previous chapters to the actinide series, with new lithium plutonium fluorides analyzed and placed into the broader context of actinide fluorides, including a new evaluation of an analogous zirconium structure. The structure of Li4ZrF8 was refined from single crystal X-ray diffraction data. Alkali zirconium fluorides are important in nuclear-relevant technologies, and zirconium is commonly employed as an analogue for tetravalent f-block elements. This result is largely consistent with prior reports, but with significant improvements in precision. The similar reaction of 242PuO2 with HF and LiF under hydrothermal conditions results in the formation of Li4PuF8 and LiPuF5. These compounds were structurally characterized using single crystal X–ray diffraction and UV–vis–NIR absorption spectroscopy. The structure of Li4PuF8 consists of [PuF8]4‒ anions that adopt a non-bridged bicapped trigonal prismatic geometry with approximate C2v symmetry. In contrast, LiPuF5 forms a dense three–dimensional network constructed from [PuF9]5‒ units that are bridged by fluoride anions. The Pu4+ cations are found within tricapped trigonal prisms. Extensive theoretical analysis of electronic and bonding interactions is included with comparison between results derived from CASSCF at different levels of theory, QTAIM, IQA, NLMO, and WBO analyses. Covalent interactions in these compounds are examined and intra–molecular trends in covalent and electrostatic interactions are discussed. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / 2019 / October 1, 2019. / actinide, fluoride, nuclear, reactor, super-heavy, synthesis / Includes bibliographical references. / Thomas E. Albrecht-Schmitt, Professor Directing Dissertation; Samuel L. Tabor, University Representative; Susan E. Latturner, Committee Member; Kenneth Hanson, Committee Member.