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The crystal and molecular structure of perylene has been refined from new three-dimensional data, confirming the gross features of the structure previously determined from two projections. The positional and thermal parameters of the carbon atoms have been refined by least-squares and differential syntheses and the hydrogen atoms have been approximately located. There are small but significant deviations from a completely planar arrangement; seemingly a result of slight intermolecular steric effects. A comparison of the measured bond lengths with those predicted by the valence-bond and molecular-orbital theory shows fairly close agreement with both sets of figures; the peri-bond lengths are 1.471-0.005 Å. In a similar vein the molecular structure of pyrene was refined by least-squares and differential synthesis treatment of new three-dimensional data. The thermal motion of the atoms was found to be anisotropic and was interpreted in terms of rigid body vibrations. Small corrections were made to the bond lengths to correct errors due to rotational oscillations. The general variation of the mean bond distances is in agreement with trends predicted by valence-bond and molecular-orbital calculations, but the individual agreements are not very good. The molecule is slightly non-planar, probably as a result of crystal packing forces. Hydroformylation of tri-O-acetyl-D-glucal yields two isomeric products and, to establish the configurations, X-ray analysis of the p-bromobenzenesulphonyl derivative of one of these has been carried out. The bromine and sulphur positions were determined from the three-dimensional Patterson function and the other atoms were located from successive three-dimensional Fourier summations. Refinement was carried out by least-squares methods. The derivative studied is 1-0-(p-bromobenzenesulphonyl)-4,5,7-tri-0-acetyl-2, 6-anhydro-3-deoxy-b-glucoheptitol, and this establishes the configurations of the triacetyl derivatives and parent polyols. The sugar ring is in the chair position with all substituents equatorial. 10-Chloro-5,10-dihydrophenarsazine crystallizes from xylene with half a molecule of xylene of crystallization in a monoclinic space group. This material rapidly loses the solvent of crystallization, the solvent-free crystals being orthorhombic. The complete structure of the orthorhombic crystals has been determined using Patterson methods to determine the arsenic and chlorine positions and a three-dimensional electron-density distribution map to locate the other atoms. All the positional and anisotropic thermal parameters were refined by least-squares. The molecule is slightly folded about the As-N axis, the angle between the two o-phenylene groups being 169°, and the chlorine atom being outside this angle. The deviation from planarity is thus not very large and it is unlikely that geometrical isomers could be isolated. / Science, Faculty of / Chemistry, Department of / Graduate

The marked physical changes in potassium boro-hydride such as decrepitation and the development of a deep blue coloration when the solid compound is exposed to ionizing radiation stimulated a study of the effects of 50 Kvp X-rays on the alkali metal borohydrides to determine the nature of the radiation induced changes such as color center formation and chemical decomposition. Methods were developed to prepare the alkali metal borohydrides in a form suitable for radiation studies. Solvents studies showed that anhydrous hydrazine was an exceptionally good solvent for potassium borohydride, the solubility being 28.3 grams KBH₄ per 100 grams at 18.5° C. The handling of hydrazine as a solvent required the construction of special apparatus. A study of the use of hydrazine as a solvent for other ionic borohydrides and/or the growth of crystals suitable for spectroscopic work is incomplete. Therefore, the spectroscopic studies on radiation induced absorption bands was done mainly with thin pressed pellets. The borohydrides of rubidium and cesium were prepared by metathesis reactions from potassium borohydride via a sulfonium borohydride. The preparation of the previously unreported trimethylsulfonium borohydride is described. Color center formation was studied by spectroscopic methods only and the F and U type centers have been tentatively identified. The thermal stability and optical bleachability of some of the radiation induced absorption bands were examined. Chemical studies of radiation damage in potassium borohydride failed to show the presence of free alkali metal. Gaseous boron hydrides were also undetectable. Mass spectrometric examination of gaseous material evolved during irradiation showed only hydrogen to be present. No gas was evolved when heavily irradiated samples of potassium borohydride were dissolved in liquid ammonia. A discussion of methods and apparatus characteristic to the radiation studies such as the X-ray generator, radiation vessels, vacuum system, and a section on radiation dosimetry is included in the thesis. The intensity of X-rays generated by the Machlett OEG-60 X-ray tube was determined by the application of the included dosimetry data together with a calorimetric measurement of the output flux of the tube. At 50 Kvp and 28 milliamperes the intensity output was found to be 0.220 cal.min.⁻¹ cm.⁻² at the tube port. Some suggestions for further work are outlined at the end of the study. / Science, Faculty of / Chemistry, Department of / Graduate

The crystal structure of 1,5-diphenyltricyclo [2.1.0.0²˒⁵] pent-3-yl p-bromobenzoate has been determined by X-ray diffraction. The crystals are triclinic, a = 5.92, b = 8.98, c = 17.85 Å, ⍺ = 89°17', β = 82°46', Ɣ = 89°50', Z = 2, space group Pī. The structure was determined with visual Cu-K[formula omitted] data by heavy atom Patterson and Fourier methods, and the positional and thermal parameters were refined by least-squares, the final discrepancy index R, being 0.16 for 1228 observed reflections. The tricyclopentane system is highly strained, with six C-C-C angles of 60°, three of 80°, and four of 90°, and an intramolecular non-bonded C...C distance of 1.99 Å. The C-C bond lengths are similar to those of normal single bonds, except for the bond common to the two three-membered rings, which may possibly be slightly shorter than the others. / Science, Faculty of / Chemistry, Department of / Graduate

The crystal structure of diferrocenyl ketone has been analyzed using Fe(Kα) X-radiation. The molecule is symmetrical about a 2-fold axis passing through the carbonyl bond. Coordinates of the iron atom were determined from two Patterson-Harker sections and coordinates of the remaining atoms were derived from subsequent three dimensional Fourier summations. Structure refinement was carried out using (block-diagonal) least squares with allowances for anisotropic temperature vibration. The R value derived from the final coordinates is 0.09. The cyclopentadienyl rings not bonded to the keto group are vibrating more than those which are; when this is taken into account the iron atom lies midway between the cyclopentadienyl rings which are planar and 3.30 Å apart. The carbon bond lengths in these rings are all the same length (1.45 Å) and the conformation of one ring with respect to the other is almost eclipsed. The intermolecular contacts are all of normal length. The molecular dimensions of anti-8-tricyclo [3,2,1,0²˒⁴] octyl p-bromobenzenesulphonate and anti-7-norborneny1 p-bromo-benzoate have been measured to assist in the interpretation of the solvolytic reactivity in norbornane derivatives. Data were collected (Cu(Kα) radiation) by counter methods in both cases; the structures were determined using the heavy atom-Patterson method and refinements were carried out using differential syntheses and (block-diagonal) least squares. The discrepancy factors derived from the final coordinates are 0.09 and 0.18 respectively. The norbornane and norbornene skeletons have symmetry m and the bond lengths are normal. The bond angles at the methylene bridge are 97° and 96° respectively, the other angles are all less than the tetrahedral angle. The angles between the planes formed by different parts of the skeleton are identical in both cases. Bond lengths and angles in the remainders of both molecules are of normal dimensions. The configuration of the cyclopropyl methylene group in anti-8- tricycle [3,2,1,0²˒⁴] octyl p-bromobenzenesulphonate is exo to the norbornane skeleton. The results indicate that there is insufficient variation in the methylene bridge bond angles to account for the difference in solvolytic reactivity. The crystal and molecular structure of ochotensine methiodide has been investigated in order to determine the chemical structure of the molecule. The data were recorded photographically using Cu(Kα) radiation and a Weissenberg equi-inclination camera; estimation of the intensities was carried out by visual methods and interfilm scales were derived from corresponding symmetry related structure amplitudes. 845 independent reflections were measured in this way. The position of the iodine atom was determined from a three dimensional Patterson function and the positions of the remaining atoms from three subsequent three-dimensional Fourier maps. Refinement of the temperature and atomic parameters was carried out by (block diagonal) least squares; the final R value was 0.11. The analysis has shown that the structure of ochotensine is similar to that postulated for ochotensimine and the position of the phenolic group on ring A has been determined. A difference synthesis was carried out to verify the positions of the atoms. The bond lengths and angles are normal but several short intermolecular contacts were observed. The planes of the two benzene rings are inclined at an angle of 94°. / Science, Faculty of / Chemistry, Department of / Graduate

Single crystal X-ray diffraction methods have been used to investigate four organic compounds, two monosaccharide derivatives and two nitrobenzene compounds: 1. methyl 3-C-(carbomethoxymethyl)-4,6-di-O-p-chlorobenzoyl-2,3- dideoxy-α-D-ribo-hexopyranoside, C(24)+H(24)+C(12)O(8); 2. 5-0-(p-bromobenzenesulphonyl)-2,2'-O-cyclohexylidene-3-deoxy-2-C- hydroxymethyl-D-erythro-pentono-1,4-lactone, C(18)H(21)BrO(7)S; 3. 2,6-dichloro-4-nitroaniline, C(6)H(4)Cl(2)N(2)O(2); 4. ethyl 3,5-dinitrobenzoate, C(6)H(8)N(2)O(6). Crystals of the di-(p-chlorobenzoate) derivative of a novel branched-chain sugar, methyl 3-C-(carbomethoxymethyl)-2,3-dideoxy-α-D-ribo-hexopyranoside, are monoclinic, space group, P2(1), a = 5•752, b = 15•436, c = 13•698 Ǻ., Β = 93•74° and Z = 2. Intensity data have been measured on an automatic diffractometer, firstly with Mo-K(α) radiation, then more accurately with Cu-K(α) radiation. Efforts to confirm the molecular structure of the derivative have been unsuccessful, although various methods of analysis have been employed; the principal approaches have been the examination of the Patterson and sharpened Patterson maps, and by direct methods, the application of the tangent formula in the phase determination procedures for noncentrosymmetric space groups. None of the methods has produced any encouraging, distinctive portions of the molecule, and at present, the investigation has been halted. The structure of "a"-D-isosaccharinic acid has been determined by crystal structure analysis of a derivative which was shown to be 5-0-(p-bromo-benzenesulphonyl)-2,2'-0-cyclohexylidene-3-deoxy-2-C-hydroxymethyl-D-erythro-pentono-l,4-lactone. Crystals are monoclinic, a = 5•757, β = 10•586, c = 16•021 Ǻ., 8 = 98•85°, Z = 2, space group P2(1). The intensities of 1319 reflections were measured with a scintillation counter and Cu-K(α) radiation, the structure was derived from Patterson and electron-density maps, and refined by least-squares methods, the final R being 0•10 for 1140 observed reflections. The absolute configuration is established, since the compound was obtained by degradation of cellulose. Each of the two five-membered rings in the derivative has an envelope conformation, with one atom displaced from the plane of the other four .In the 1,3-dioxolane ring, the displacement is 0•49 Ǻ.; the γ-lactone ring is less prominently bent, with displacement only 0•14 Ǻ. The bond distances and valency angles in the molecule do not differ significantly from the usual values, and the intermolecular distances correspond to van der Waals' interactions. Crystals of 2,6-dichloro-4-nitroaniline are generally twinned; they are monoclinic, space group P2(1)/c, a = 3•723, b = 17•833, c = 11•834 Ǻ., 8 = 94•12°, Z = 4. Intensity data were collected for one of the twins on an automatic diffractometer. The coordinates of the two chlorine atoms were found in a Patterson map and all the other atoms in electron-density and difference Fourier maps. The structure was refined by full-matrix least-squares methods to R = 0•038. There are only slight deviations from overall planarity of the molecule, the amino and nitro groups being rotated by 6•3 and 7•2° respectively out of coplanarity with the benzene ring. The amino group appears to be held nearly coplanar with the benzene ring by intermolecular N-H...0 and intramolecular N-H...C1 / Science, Faculty of / Chemistry, Department of / Graduate

A low temperature x-ray powder diffraction attachment for use on the vertical goniometer of a diffractometer is described. We have found that diffraction patterns obtained with the attachment mounted on the goniometer are of comparable quality to those obtained on the goniometer itself. Using this attachment, the lattice parameter discontinuities associated with a charge density wave phase transition in 1T-TaS₂ near T=200K are measured with an accuracy greater than that of any previous results. Electrochemically prepared samples of Li xTiS₂ near x=0.16 are studied at room temperature and below. Clear evidence for the formation of a stage two superlattice at low temperatures was not obtained. / Science, Faculty of / Physics and Astronomy, Department of / Graduate