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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 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

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

In contrast to 1,1'-binaphthyl, racemic 4,4'-dimethyl-1,1'-binaphthyl does not undergo spontaneous resolution upon heating from room temperature to just below the melting point. Optically active dimethyl binaphthyl may be obtained by seeding the racemic melt site optically active naphthidine. The crystal structures of both the racemic and optically active dimethyl binaphthyls were solved in the hope of understanding the above observations. The racemate crystallizes in the monoclinic space group C2/c with cell parameters a=13.225, b=10.768, c= 11.572 Å and β=114.040. There are four molecules per unit-cell; two have the B and two have the S configuration. The structure was solved using direct methods and refined to R=0.074. There is a 3° head in the plane of the naphthalene residues, which are cis-oriented with an angle of 68° between them. The optically active form belongs to one of the tetragonal space groups P4₁2₁2 or P4₃2₁2 with cell parameters a = b = 8.3031 and c = 23.706 Å. Direct methods sere used to solve the structure and the final R was 0.060. There are four molecules per unit-cell of identical configuration, but it could not be determined whether this was R or S. The naphthalene residues show a 2.7° bend and are also cis-oriented, but with an angle of 80° between them. Bond lengths and angles are consistent with values previously reported for 1,1'-binaphthyl and naphthalene. The racemate packs somewhat more efficiently and perhaps for this reason it is slightly more stable than the optically active form- It is difficult however to explain the difference in behaviour between the methylated and unmethylated binaphthyls on the basis of these results alone. Further studies would include the crystal structures of optically active 1,1'-binaphthyl and various naphthidines. / Science, Faculty of / Chemistry, Department of / Graduate

The structures of four 4aβ,5,8,8aβ-tetrahydro-1 -naphthoquin-4-ol derivatives have been studied and related to their observed photochemical reactivity. H-abstractions are dominant in the solid state photolyses of these compounds because of their conformations and the topochemical control by the lattice. All structures have been solved by direct methods and refined by least squares procedures. The 2,3,6,7-tetramethyl-4α-ol derivative, C₁₄H₂₀O₂, is monoclinic, space group C2/c, a = 13.898(3), b = 5.228(1), c = 17.316(3) Å, β = 97.442(7)° and Z = 4. This structure was refined to R = 0.058 for 888 reflections. The 2,3- and 6,7-dimethyl-4α-ol compounds-C₁₂H₁₆O₂, are orthorhombic, space group P2₁2₁2₁, and monoclinic, space group 2₁/c, respectively. For the 2,3-derivative, a = 5.148(1), b = 12.269(2), c = 16.478(3) Å, Z = 4 and the refinement of 671 data led to an R of 0.031. The 6,7-compound, a = 9.242(3), b = 22.724(3), c = 5.139(2) Å, β = 102.7(1)°, Z = 4, was refined to R = 0.032 for 626 data. 2,3,4σ,4aβ,6,7,8aβ-heptamethyl-4β-ol, C₁₇H₂₆0₂, is monoclinic, space group P2₁/c, a = 7.497(2), b = 16.792(3), c = 12.687(3) Å, β = 105.30(1)° and Z = 4. An R-value of 0.041 was obtained from the refinement of 1934 reflections. The above compounds have similar conformations which are favorable to H-abstraction reactions. The 6,7-dimethyl-1α,4α-diol C₁₂H₁₈0₂, crystallizes in the monoclinic system, space group P2₁/c, a = 13.870(2), b = 18.025(4), c = 9.236(1) Å, β = 108.098(6)° , Z = 8 and was refined to R = 0.032 for 1461 reflections. The diol compound adopts the same conformation as those above but is not photoreactive. The following four compounds were derived from either tetrahydronaphthoquinol progenitors or their oxidized forms, tetrahydronaphthoquinones. A twistane-1ike structure, twistenone C₁₀H₁₀0₂, was found to crystallize in the monoclinic system, space group P2₁/n, a = 6.381(2), b = 19.454(2), c = 6.708(2) Å, β = 1 06.24( 1 )° and Z = 4. Refinement of 930 reflections converged at R = 0.037. 5-(2,3-dimethylphenyl)-ƴ-butyrolactone crystals, C₁₂H₁₅O₂ are monoclinic, space group P2₁/n, a = 10.847(3), b = 6.924(1), c = 13.654(4) Å, β = 95.22(1)° and Z = 4. The structure was refined to R = 0.057 for 569 reflections. It was hoped that elucidation of this structure would aid in determining the intermediate compound from which it was formed. The methylene ketone C₁₇H₂₄0, derived from the acetylation product of the previously described heptamethyl-4β-ol, is monoclinic, space group P2₁/a, a = 12.374(2), b = 8.771(1), c = 13.743(2) Å, β = 104.027(6)° , Z = 4 and refined to R = 0.037 for 1369 data. A reaction designed to pinacolize a diketone cage compound resulted in a different product from which the hydroxy mesylate derivative C17H280„S, was formed. The crystals are monoclinic, space group P2,/c, a = 9.246(2), b = 10.938(1), c = 17.335(4) Å, β = 102.11(1)° and Z = 4. Refinement converged at R = 0.042 for 2995 reflections. / Science, Faculty of / Chemistry, Department of / Graduate

ABSTRACT Part one of this thesis contains the x-ray crystal structure analyses of six compounds related to natural product chemistry. The first three analyses were performed in order to identify two isomers, separated by chromatography, that were potential intermediates in the syntheses, of stemodin. and aphidicolin, and differed only in the orientation of a cyclobutyl moiety. The first eluted isomer was shown to be a β-cyclobutyl tricyclic enone (C₂₂H₃₂O₃ monoclinic, space group P2₁/n, a = 11.832(1), b = 11.423(1), c = 14.637(1) Å, β = 98.71(2)°, Z = 4, solved by direct methods and refined to R = 0.034 for 2052 observed reflections). The second eluted isomer was the c-cyclobutyl species (C₂₂H₃₂O₃, monoclinic, space group P2₁/n, a = 15.722(4), b = 7.463(2), c = 17.213(6) Å, β =- 104.67(1) ⁰, Z = 4, solved by direct methods- and- refined to R = 0.040 for 702 observed reflections). The third analysis was of the p-bromobenzoate derivative of the second eluted isomer, and confirmed the c-cyclobutyl structure (C₂₉H₃₇BrO₄, triclinic, space group PT, a = 11.023(2), b = 11.877(1), c = 10.900(1) Å, α = 90.461(8), β = 111.57(1), ƴ = 80.51(1)°, Z = 2, solved by Patterson methods and refined to R = 0.032 for 2715 observed reflect ions). The fourth structure was also a p-bromobenzoate derivative of a system involving a four-membered ring, and was undertaken to verify the 1,4-homoenol structure of camphor-1,4-homoenol p-bromobenzoate (C ₁₇H₁₉BrO₂, orthorhombic, space group P2₁2₁2₁, a = 6.875(1), b = 8.522(2), c = 26.658(6) Å, Z = 4, solved by both direct and Patterson methods and refined to R =0.045 for 697 observed reflections). The last two structures of this part proved to be crystallographically difficult. One was the previously unknown structure of raucubaine, an indole alkaloid isolated from the plant Rauwolfia salicifolia griseb. (C₂₀H2₂₄N₂0₃, monoclinic, space group P2₁, a = 7.2179(3), b = 12.8169(7), c = 9.1996(2) Å, β = 93.040(3)°, Z = 2, solved by direct methods (with great difficulty) and refined to R = 0.046 for 1700 observed reflections). The other was a sugar that had remained unsolved for fourteen years (C₂₄H₂₄Cl₂O₈, monoclinic, space group P2₁, a = 5.752(3), b = 15.436(3), c = 13.698(3) Å, β = 93.74(3)°, Z = 2, solved by direct methods (with great difficulty) and refined to R = 0.042 for 898 observed reflections). Part two contains two optically active structures as part of a project concerning spontaneous resolution in binaphthyl systems: the first being naphthidine (C₂₀H₁₆N₂, tetragonal, space group P4₁2₁2 or P4₃2₁2, a = 7.945(1), c = 24.264(5) Å, Z = 4, solved by direct methods and refined to R = 0.068 for 548 reflections) and the other 1, 1'-binaphthyl (C₂₀H₁₄, tetragonal, space group P4₁2₁2 or P4₃2, a = 7.164(2), c = 27.70(1) Å, Z = 4, solved by direct methods and refined to R = 0.030 for 562 observed reflections). These structures are compared to those of several related compounds. / Science, Faculty of / Chemistry, Department of / Graduate

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