This study was concerned with the effects of aerosols on the kinetics of disappearance of atomic oxygen. Atomic oxygen was generated by a 2450 MHz microwave discharge, and the kinetics of disappearance measured in a fast flow system using N0₂ titration. The recombination coefficient, for heterogeneous wall recombination was determined for clean Pyrex, H₂SO₄ coated wall, and (NH₄)₂SO₄ coated wall. The values of γ were 4.97 x 10^-5, 2.05 x 10^-5, and 1.90 x 10^-5 respectively. A rapid exothermic chemical reaction was found to occur between atomic oxygen and NH₄C1; the products, as determined by mass spectrometry, were NH₃, NO, H₂O, HC1. An NH₄Cl aerosol was generated by gas phase reaction of NH₃(g) with HCl(g), The aerosol particles were approximately spherical and nearly monodisperse with a mean diameter of 1.6 ± .2 μm. The rate constant {k_AERO) for the disappearance of atomic oxygen in the presence of an NH₄Cl aerosol was measured. For an aerosol concentration of 4.75 x 10³ µg/m³. a value of k_AERO = 2.75 ± .5 sec^-1 was found, / M.S.

Ph. D.

M.S.

One of the most widely studied “exotic atoms" in Chemistry and Physics is positronium. Positronium (Ps) is the bound state of an electron and positron. It is formed in two ground states, para-positronium (p-Ps) and ortho-positronium (o-Ps) whose lifetimes in free space are 0.125 nsec and 140 nsec respectively. When thermalized o-Ps forms a complex with a molecule, the electron density at the position of the positron will be drastically increased thus shortening its lifetime. A study was performed to evaluate what role the solvent plays in stabilizing the complexes formed between Ps and nitroaromatics in solution and the various thermodynamic variables associated with these processes. This study also included the evaluation of the effects displayed by several different solvents on complexes formed between Ps and CuCl₂. The interpretation of the solvent effects of Ps reactions in terms of the "bubble shrinkage model" was tested using the results obtained in the reactions of Ps with various inorganic and organic molecules in different solvents. It was found that this model is definitely not applicable below a certain critical viscosity of the solvent and appears to be restricted to diffusion controlled reactions. The fact that the reactivity of Ps towards nitroaromatics is drastically reduced when the latter molecules are already complexed with other conventional molecules can be utilized to determine the molecular formation constant, K_c, for inclusion Compounds. A study was made using Ps as a probe to provide valuable information about the influence of steric factors on the ability of guest molecules to bind in the cavity of cyclohexaamylose, / Ph. D.

A digital computer was used to measure accurate gas chromatographic peak symmetry, position and dispersion by central statistical moments. Benzene samples were chromatographed on squalane for columns of 3, 6 and 12 foot lengths and 1/8", 1/ 4" and 1/2" diameters as a function of sample size. Peak symmetry was monitored by measuring skew, γ₁ , and "excess," γ₂ two quantities derived from the higher central moments. Skew was found to increase in a positive manner for tailing peaks, pass through a maximum and approach a limiting step form for extremely overloaded columns. Skew could be used to indicate saturation of the liquid phase when it passes through a maximum. Negative skew for fronting peaks also approached a zero limiting form. Excess, γ₂ was found to decrease rapidly for all columns. A few microliters of sample were sufficient to cause significant negative values of excess. Excess provides a semi-quantitative measure of column capacity. Three general types of peak shapes were observed with increasing sample sizes: 1) gaussian behavior at very low sample sizes; 2) distorted peaks suitable characterized by central moments at normal analytical size samples; and 3) highly distorted peaks at larger sample sizes where central moments no longer reflect the step shapes observed. Moments can be used to set limits on sample sizes which will produce these highly distorted peaks. Two moment related measures of skewness were also calculated. Pearson’s skew, (Mean - Mode)/(variance)^½, along with Pearson’s β, γ measure of skewness, were found to qualitatively reflect peak shape behavior only in the region of analytical sample sizes. Pearson's skew is subject to difficult interpretation due to equivalent modal values for large samples and the β, γ measure was insensitive to fronting peaks. Third and fourth central moments were observed to have regular behavior as a function of sample size. A moment definition of resolution was derived R = 0.5 (M(1)₂ - M(1)₁) /( √M(2)₁ + √M(2)₂ ) where M(1) = mean and M(2) = variance. This definition was used to compare solvent efficiency for the separation of benzene and cyclohexane on three liquid phases, squalane, dinonalphalate and TRIS. In terms of equivalent throughput, defined as moment resolution per unit time per gram of sample, TRIS was found to be 175 times more selective than squalane. A preparative chromatograph was built with four thermal conductivity detectors at 50' intervals in a 200' x 3/8" column. Column efficiency was measured by comparison of moment parameters at the end of each 50' section. The column was operated both at normal, high pressure drop (ambient outlet pressure) and low differential pressure (constricted outlet). The condition of high pressure drop caused acceleration of samples through the last two column sections and resulted in much poorer column efficiency. The low differential pressure column, inlet 350 psi, outlet approximately 150 psi produced a more linear velocity and greater column efficiency. In fact 100 feet of the low differential pressure column generated the same resolution as 200 feet of the high pressure column. For most chromatographic peaks manual methods of peak evaluation are subject to significant operator errors due to the subjective nature of assigning base width and peak retention time. The use of moments greatly increases the accuracy of two important measurements; (1) retention time as measure from the first moment and (2) resolution for preparative scale samples as measured from the first and second moments. The method of moments provides an accurate means of measuring retention time, dispersion, resolution and preparative scale equivalent throughput. / Ph. D.

The method of spin projection was examined by developing and applying computer programs to calculate projected semi-empirical and ab initio unrestricted Hartree-Fock (UHF) wavefunctions. The electronic spectra of naphthalene, anthracene, naphthacene and pentacene were calculated using the Pariser-Pople-Parr (PPP) Π-electron approximations and both UHF and configurational interaction (CI) techniques. The results of both techniques were compared with experimentally determined spectra with reasonable agreement between the CI and projected UHF results. While the CI calculations generally produced lower energies for the triplet states than the UHF calculations, the spectra from UHF calculations were in somewhat better agreement with experiment. Anomalies encountered with degeneracies and the presence of open shell ground states are also discussed. The geometry of monohomocyclooctatetraene anion radical (MHCOT) was studied using spin projection of the UHF INDO wavefunction. The theoretical molecular geometry was varied until the experimental hyperfine coupling constants matched hyperfine constants obtained from using both projected and unprojected UHF wavefunctions. The two types of calculations resulted in slightly different energies and geometries with the projected calculations giving a higher energy for the doublet state; essentially no differences were noted in the bond orders obtained from the two types of calculations. The geometry from the projected calculations was a somewhat more strained conformation than the geometry from the unprojected calculation. Ab initio UHF calculations with spin projection were performed on H₂O(+) to compare the energies of pure spin states from ab initio multiconfigurational self-consistent field with CI. (MCSCF/CI) with those from spin projection. The MCSCF/CI calculations are superior to the UHF plus spin projection calculations. This result will always be observed when the UHF wavefunction is very close to a pure spin state before spin projection. The dissociation of CF₂O was studied using ab initio wavefunctions. The energies of the unprojected UHF wavefunctions were examined along with those for the dissociated CF₂ + O fragments. Good agreement exists between the calculated and experimental vertical ionization potentials for CF₂0 at the equilibrium geometry. / Doctor of Philosophy

Ph. D.

no abstract provided by author / Ph. D.

The work described in this dissertation represents an effort to extend the application of Nuclear Quadrupole Resonance spectroscopy to the study of transition element compounds. Using a conventional noise controlled superregenerative spectrometer compounds of cobalt, copper and molybdenum have been investigated. Three biscobalt(tetracarbonyl) tin(II) compounds were investigated and the ⁵⁹Co resonances measured in each. Each compound exhibited a doublet indicative of two crystallographic inequivalent sites. The asymmetry parameters were all between 0.005 and 0.10 indicating little distortion of the cobalt environments from the expected C₃_v symmetry. The coupling constants as obtained by use of a series approximation for the transition frequencies and confirmed by a frequency ratio plot were Cl₂ Sn [Co(CO)₄]₂ -146.9MHz, (C₆H₅)ClSn [Co(CO)₄]₂ -137.7 MHz, (C₆H₅)₂Sn[Co(CO)₄]₂ -112.9 MHz. The observed coupling constants correlate with the inductive effects of the substituents in the tin. The study of several Copper(I) coordination compounds represents the first known attempt at using Cu nuclear quadrupole coupling constants to study bonding in a situation other than an isolated compound. Assuming zero asymmetry parameters the following ⁶³Cu coupling constants were observed; Cu(tu)₂NO₃ -50.18 MHz, Cu(tu)₂Cl - 41.41 MHz, Cu(tu)₂Br -32.62 MHz, Cu(etu)₂ClO₄ - 45.76 MHz, [Cu(etu)₄]₂ SO₄ - 63.12 MHz, Cu(etu)₂C1 - 55.72 MHz, Cu(etu)₂Br - 64.02 MHz, Cu(dmtu)₃C1 - 77.60 MHz. The ligands used were tu-thiourea, etu-ethylene thiourea, and dmtu -N,N’ dimethylthiourea. The crystal structures of only Cu(tu)₂C1 and Cu(dmtu)₃Cl are known making direct comparison difficult. The general increase of the coupling constants with ligand substitution correlates with the partial charge on the sulfur atom of the free ligand. The reversal of the order of the coupling constants between the thiourea and ethylene thiourea halides indicates an appreciable ion contribution to the coupling constant from the halogen. The observation of ⁷⁹Br resonance at 38.83 MHz in Cu(etu)₂Br also confirms this point. By using sp² and sp³ hybridization schemes for Cu(tu)₂C1 and Cu(dmtu)₃Cl the coupling constants were calculated to be 36.0 MHz and 17.27 MHz respectively. This represents reasonable agreement in view of the uncertainties in the Sternheimer factor used and the approximate nature of the model. The allowance for d_π - d_π bonding between the Cu and S atoms decreases the calculated constants indicating that such bonding probably is of little importance. Resonance were observed for Mo isotope in both MoOCl₄ and MoO₂Cl₂. Both possible Mo resonances as well as the Cl resonances were observed. The particular isotope to which the resonances belong is as yet undetermined since those belonging to the other Mo isotopes with. I= 1 will be outside the range of available instrumentation. / Ph. D.

A new approach in the syntheses of 3-bromo-2-butanone and 2-bromo-3-fluorobutane has been developed. All attempts to alkylate the sodium salt of diethyl malonate, ethyl acetoacetate, or diethyl acetamidomalonate with 2-bromo-3-fluorobutane failed. New phosphonoacetates, tert-butyl and benzyl diethylphosphono-acetates were prepared as very versatile intermediates in the syntheses of carboxylic acids. Methyl-, ethyl-, tert-butyl-, and benzyl 4-fluoro-3-methyl-2-pentenoates were synthesized in high yields by the Horner-Emmons reaction. The reaction is stereoselective and gave E and Z form in 75:25 ratio as determined from proton and fluorine nmr spectra. A long-range coupling was observed in fluorine nmr spectrum of 3-fluoro-2-butanone. From the ethyl 4-fluoro-3-methyl-2-pentenoate, ethyl 2-bromo-4-fluoro-3-methyl-2-pentenoate was prepared, but the latter could not be reduced under the conditions of catalytic hydrogenation. Ethyl 2-chloro-4-fluoro-3-methyl-2-pentenoate was prepared from 3-fluoro-2-butanone and ethyl diethylphosphonochloroacetate, but could not be reduced. Catalytic hydrogenation of alky 4-fluoro-3-methyl-2-pentenoates gave the corresponding saturated esters in high yields. Treatment of alkyl 4-fluoro-3-methylpentanoates with lithium diisopropylamide and bromine at -78° yielded the corresponding 2-bromoderivatives. Methyl-, ethyl-, and tert-butyl 2-bromo-4-fluoro-3-methyl-pentanoates were treated with sodium azide to give the corresponding 2-azido derivatives which were further reduced into methyl-, ethyl-, and tert-butyl 2-amino-4-fluoro-3-methylpentanoates. / Ph. D.