High resolution rotational spectra of ¹⁰BH₃CO, ¹¹BH₃CO, ¹¹BD₃CO, PH₂D and CD₃CN were studied to obtain information concerning the electronic and magnetic properties of these molecules. From the analysis of the hyperfine structure of the rotational spectra of the molecules the following constants were determined: rotational constants (B₀), nuclear quadrupole coupling constants (eOq [x], spin-spin constants D (X-Y) and spin rotation constants (C[x]). The two instruments used in these experiments were a Stark modulated microwave spectrometer and a molecular beam maser spectrometer. The J = 0 to 1, F₁ = 3 to 3 and F₁ = 3 to 4 transitions of ¹⁰BH₃CO were studied. The molecular constants in KHz which were derived from the spectral analysis were: B(,0) = 8980060.3 (+/-) 1.0, eQqₐₐ (¹⁰B) = 3463.- (+/-) 8.0, C(¹⁰B) = .2 (+/-) .2, D(¹⁰B-H) = -2.8 (+/-) .2, D(H-H) = -7.2 (+/-) .5 and C(H) = 0.0 (+/-) .7. All three of the F₁ components of the J = 0 to 1 rotational transition of ¹¹BH₃CO were observed. The molecular constants in KHz which were obtained from the data analysis were: B₀ = 8657333.8 (+/-) .6, eQqₐₐ (¹¹B) = 1661.9 (+/-) 2.3, C(¹¹B) = .7 (+/-) .3, D(¹¹B-H) = 8.3 (+/-) .4, D(H-H) = -6.8 (+/-) .2 and C(H) = .4 (+/-) .4. Only spectra of the J = 0 to 1, F₁ = 3/2 to 3/2 transition of ¹¹BD₃CO were obtained. From the analysis of the spectra the following molecular constants were derived: eQqₐₐ (D) = -48.5 (+/-) 2.3, eQq(,zz)(D) = 116.9 (+/-) 5.4, C(D) = 0.0 (+/-) .8 and D(¹¹B-H) = -1.2 (+OR-) .3. The investigation of the 4₀₄ to 4₁₄ and 1₁₁ to 1₀₁ rotational transitions of PH₂D was unsuccessful in determining any molecular parameters. The spectra of the 4₀₄ to 4₁₄ rotational transition were not amenable to analysis and no spectra were obtained for the 1₁₁ to 1₀₁ rotational transitions. The three components of the J = 0 to 1 rotational transitions of CD₃CN were studied with the maser in the two cavity configuration. The constants in KHz which were determined were: B₀ = 7857978.7 (+/-) .1, eQqₐₐ(N) = -4229.2 (+/-) .6, eQqₐₐ(D) = -55.1 (+/-) .4, eQq(,zz)(D) = 165.5 (+/-) 5.0, C(,N) = 1.7 (+/-) .1 and C(,D) = 0.0 (+/-) .03.

No description available.

Tsang Hing Wa = 梯度粒子系統的扭轉運動 / 曾慶華. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 66-68). / Text in English; abstracts in English and Chinese. / Tsang Hing Wa = Ti du li zi xi tong de niu zhuan yun dong / Zeng Qinghua. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Localization --- p.1 / Chapter 1.1.1 --- Localization by Potential Confinement --- p.1 / Chapter 1.1.2 --- Localization by Interference --- p.2 / Chapter 1.2 --- Graded Materials --- p.2 / Chapter 1.3 --- Rotational Motion --- p.3 / Chapter 2 --- Torsional Motion of Rotating Particles with Graded Couplings / Chapter 2.1 --- Linear Couplings --- p.5 / Chapter 2.1.1 --- Model and Formalism --- p.5 / Chapter 2.1.2 --- Gradient in Coupling Constant --- p.7 / Chapter 2.1.3 --- Gradient in Moment of Inertia --- p.8 / Chapter 2.1.4 --- Numerical Results --- p.9 / Chapter 2.1.5 --- Discussion and Conclusion --- p.14 / Chapter 2.2 --- Non-Linear Couplings --- p.14 / Chapter 2.2.1 --- Model and Formalism --- p.14 / Chapter 2.2.2 --- Gradient in Coupling Constant --- p.16 / Chapter 2.2.3 --- Gradient in Moment of Inertia --- p.16 / Chapter 2.2.4 --- Numerical Results --- p.17 / Chapter 2.2.5 --- Discussion and Conclusion --- p.29 / Chapter 3 --- Torsional Motion of Rotating Particles with graded potential --- p.30 / Chapter 3.1 --- Linear Interaction --- p.30 / Chapter 3.1.1 --- Model and Formalism --- p.30 / Chapter 3.1.2 --- Gradient in On-site Torsional Potential --- p.32 / Chapter 3.1.3 --- Numerical Results --- p.33 / Chapter 3.1.4 --- Discussion and Conclusion --- p.43 / Chapter 3.2 --- Non-linear Interaction --- p.43 / Chapter 3.2.1 --- Model and Formalism --- p.43 / Chapter 3.2.2 --- Numerical Results --- p.45 / Chapter 3.2.3 --- Chaotic Effect --- p.62 / Chapter 3.2.4 --- Discussion and Conclusion --- p.64 / Chapter 4 --- Conclusion --- p.65 / Bibliography --- p.66

Au Yuen-yee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 140-152). / Abstracts in English and Chinese. / Abstract --- p.iii / Acknowledgements --- p.v / Chapter Chapter One: --- General Background and Introduction --- p.1 / Chapter 1 -1 --- Introduction --- p.1 / Chapter 1-2 --- Three-Bond Coupling Constants (3J) --- p.1 / Chapter 1-2-1 --- Development of the Karplus Equation --- p.1 / Chapter 1-2-2 --- Application of3J in the Conformational Analysis of Nucleic Acid --- p.4 / Chapter 1-2-3 --- Problem of Accuracy for3 J Measurement --- p.7 / Chapter 1-3 --- Two-Bond Coupling Constants (2J) --- p.7 / Chapter 1-3-1 --- The Use of the Projection Method --- p.7 / Chapter 1-3-2 --- 2J Coupling Constant Involving Hydrogen Bonds --- p.8 / Chapter 1-4 --- One-Bond Coupling Constants (1J) --- p.10 / Chapter 1-5 --- Conclusion --- p.11 / Chapter Chapter Two: --- Experimental Section / Chapter 2-1 --- Introduction --- p.12 / Chapter 2-2 --- Heteronuclear Multiple-Quantum Coherence (HMQC) Experiment --- p.12 / Chapter 2-3 --- Experimental Section --- p.15 / Chapter 2-3-1 --- Sample Preparation --- p.15 / Chapter 2-3-2 --- NMR Spectroscopy --- p.16 / Chapter Chapter Three: --- Theory of Nuclear Spin-Spin Coupling Constants --- p.18 / Chapter 3-1 --- Introduction --- p.18 / Chapter 3-2 --- Application of Finite Perturbation Theory on Nuclear Spin-Spin Coupling --- p.18 / Chapter 3-3 --- Methodology --- p.22 / Chapter Chapter Four: --- DFT and NMR Study of1JCH Coupling Constants --- p.28 / Chapter 4-1 --- Introduction --- p.28 / Chapter 4-2 --- Nomenclature and Definition of Structural Parametersin DNA and RNA --- p.28 / Chapter 4-2-1 --- "Nomenclature, Symbols and Atomic Numbering Schemes" --- p.28 / Chapter 4-2-2 --- Definition of Torsion Angles and their Rangesin Nucleotides --- p.31 / Chapter 4-2-3 --- Description of the Furanose Ring --- p.31 / Chapter 4-3 --- Results and Discussion --- p.37 / Chapter 4-3-1 --- Basis Set Effect --- p.37 / Chapter 4-3-2 --- Relative Conformational Energy Profiles --- p.37 / Chapter 4-3-3 --- Comparison of the Dependence of 1JCH Coupling Constants on Conformational Changes With and Without the DNA Backbone --- p.40 / Chapter 4-3-4 --- Effect of Backbone 3'- and 5'-Phosphate --- p.42 / Chapter 4-3-5 --- Effect of Glycosidic Torsion Anglex --- p.49 / Chapter 4-3-6 --- Effect of Ring Conformation with Fixed Glycosidic Torsion Anglex --- p.52 / Chapter 4-3-7 --- Effect of Torsion Angle α --- p.52 / Chapter 4-3-8 --- Effect of Torsion Angle β --- p.53 / Chapter 4-3-9 --- Effect of Torsion Angle γ --- p.56 / Chapter 4-3-10 --- Effect of Torsion Angle ε --- p.59 / Chapter 4-3-11 --- Effect of Torsion Angle ζ --- p.61 / Chapter 4-3-12 --- Effect of Base Pairing --- p.65 / Chapter 4-3-13 --- Effect of Base Stacking from the (n-1) and (n+1) Base --- p.65 / Chapter 4-3-14 --- Comparison of Experimental and Theoretical Data --- p.68 / Chapter 4-4 --- Conclusion --- p.74 / Chapter Chapter Five: --- DFT Study of 2JCH and 3JCH Coupling Constants --- p.79 / Chapter 5-1 --- Introduction --- p.79 / Chapter 5-2 --- Results and Discussion on 2JCH Coupling Constants --- p.79 / Chapter 5-2-1 --- Effect of Backbone 3'- and 5'-Phosphate --- p.79 / Chapter 5-2-2 --- Effect of Ring Conformation with Fixed Glycosidic Torsion Anglex --- p.82 / Chapter 5-2-3 --- Effect of Glycosidic Torsion Anglex --- p.87 / Chapter 5-2-4 --- Effect of Torsion Angleγ --- p.87 / Chapter 5-2-5 --- Effect of Torsion Angle ε --- p.90 / Chapter 5-2-6 --- Effect of Base Pairing --- p.90 / Chapter 5-2-7 --- Effect of Base Stacking from the (n-1) and (n+1) Base --- p.90 / Chapter 5-3 --- Results and Discussion on 3JCH Coupling Constants --- p.95 / Chapter 5-3-1 --- Effect of Backbone 3'- and 5'-Phosphate --- p.95 / Chapter 5-3-2 --- Effect of Ring Conformation with Fixed Glycosidic Torsion Anglex --- p.95 / Chapter 5-3-3 --- "Effect of Different Torsion Angles (X,α,β,γ,ε,and ζ)" --- p.100 / Chapter 5-3-4 --- Effect of Base Pairing --- p.100 / Chapter 5-3-5 --- Effect of Base Stacking from the (n-1) and (n+1) Base --- p.105 / Chapter 5-4 --- Conclusion --- p.105 / Chapter Chapter Six: --- Conclusion --- p.111 / Appendix A Product Operator Formalism on HMQC Pulse Scheme --- p.113 / Appendix B Finite Perturbation Theory --- p.115 / Appendix C Supplementary Figures of Chapter Four --- p.118 / Appendix D Some of the NMR Spectra --- p.134 / References --- p.140

Thesis (M. Sc. (Chemistry)) --University of Limpopo, 2018 / The dissertation describes the use of 2-benzenesulfonyloxyquinoxaline as a good coupling partner for different amine substrates. The palladium-mediated cross- coupling of aryl electrophiles and amines has become a widely used method of constructing arylamine frameworks. The formation of carbon-nitrogen bonds was accomplished via palladium-catalysed Buchwald-Hartwig amination employing different amine substrates to yield substituted quinoxaline-2-amines compounds in good to moderate yields. Buchwald ligands (Xphos, tButylxphos and BrettPhos), were varied with different amine substrates in an attempt of improving the yields. Compounds 81a N-phenylquinoxalin-2-amine and 82b, N-benzylquinoxalin-2-amine were obtained with the yield over 70 % employing Xphos as the ligand. Significant attention has also been given to the application of cross coupling reaction protocols in substrates bearing electron withdrawing substituents. The presence of deactivating groups on the arylamine such as fluoro, nitro and iodo proved to be a challenge as only few compounds were synthesised in moderate yields. Compound 81b, N-(4-fluorophenyl)quinoxalin-2-amine which has electronegative atom attached, showed significant improvement when employing tButyl-Xphos ligand rather than XPhos since the yield improved from 10 % to 71 %. Furthermore, nucleophilic substitution on Buchwald-Hartwig coupled compounds by treating them with alkyl iodides was successful when using methyl and ethyl electrophiles on the N-H group of 81a 2-quinoxalineamine. The synthesised quinoxaline derivatives comprised 7 novel compounds. The in vitro analysis on anti-tubercular screening against H37RvMA strains of Mycobacterium tuberculosis was conducted on 9 compounds. The results revealed none of the compounds to have promising inhibition percentages against Mycobacterium tuberculosis when compared with rifampicin which was used as a positive control. Screening against malaria with chloroquine as the control also did not yield any active compounds.

Graduate / 0485

Graduate / 0485

Orientador: Roberto Rittner Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-08T22:55:18Z (GMT). No. of bitstreams: 1 Vilcachagua_JanainaDantas_M.pdf: 7602676 bytes, checksum: c8ad06bb13f22f25be4a54757dfeb0e2 (MD5) Previous issue date: 2007 / Resumo: Estudaram-se as interações de orbitais e seus efeitos nas constantes de acoplamento JHH e JCH em 1,3,5-trioxano, 1,3,5-tritiano e 1,3,5-tritianos monosubstituídos, onde os substituintes foram os halogênios: flúor, cloro, bromo e metil por dados de ressonância magnética nuclear e cálculos teóricos. Todos os cálculos foram realizados com os programas GAUSSIAN 98 e 03. Os cálculos de otimização de geometrias foram realizados em nível MP2 e a função de base aug-cc-pVTZ. Os cálculos para estudo das interações hiperconjugativas foram feitos com o programa NBO. As constantes de acoplamento foram calculadas utilizando a teoria de perturbação CP-DFT. Obtiveram-se os espectros de RMN de H e de C a temperatura ambiente e a baixa temperatura para obtenção dos valores das constantes de acoplamentos experimentais. A análise conjunta dos dados teóricos e experimentais para o 1,3,5-trioxano e 1,3,5-tritiano mostrou a influência das interações hiperconjugativas nxs*C-HEq, nxs*C-HAx, e nxs*C-X, onde o X pode ser o átomo de oxigênio ou enxofre, nos valores das constantes de acoplamento JCHax, JCHeq e JHH. A análise conjunta dos dados teóricos e experimentais para 1,3,5-tritianos monosubstituídos mostrou a influência dos átomos eletronegativos, flúor, cloro e bromo, no valor da constante de acoplamento JCHax no carbono 6 através do efeito eletrostático. As constantes de acoplamento JCHax e JCHeq, no carbono 2, sofrem influência direta do substituinte eletronegativo. A presença do grupo metila não mostrou nenhum efeito nos valores das constantes de acoplamento estudadas. / Abstract: The present work reports the NMR data and theoretical calculations of orbital interactions and their effects on JHH and JCH coupling constants in 1,3,5-trioxane, 1,3,5- trithiane and 2-substituted 1,3,5-trithianes, where the substitutents are fluorine, chlorine, bromine and methyl. The calculations were carried out with the Gaussian 98 and 03 package of programs. The aug-cc-pVTZ basis sets were employed for geometries optimizations at level MP2. The energies of hyperconjugative interactions were calculated with the NBO program. The coupling constants were evaluated within the CP-DFT perturbative approach. The H and C spectra were recorded for all compounds at room and low temperature, for obtained the determination of coupling constants. The experimental results and those from theoretical calculations showed the influence of hyperconjugative interactions nxs*C-HEq, nxs*C-HAx, e nxs*C-X, where X is oxygen or sulfur atoms, on JCHax, JCHeq and JHH coupling constants in 1,3,5-trioxane and 1,3,5-trithiane. The experimental results and those from theoretical calculations showed the influence of electrostatic effects for JCHax coupling constant in 2-substituted 1,3,5-trithianes with electronegative atoms: fluorine, chlorine and bromine. For carbon 2, the JCHax and JCHeq coupling constants showed the direct influence of the electronegative atom. The alkyl group, methyl, did not present any effects on the coupling constants in study. / Mestrado / Quimica Organica / Mestre em Química

The study consists of three major areas of research. First, the dihedral angle dependence of vicinal carbon-carbon coupling constants is determined for aliphatic and alicyclic carboxylic acids wherein the formal hybridization and substituents are held constant. Second, the magnitudes and relative signs of long-range carbon-carbon coupling constants in a. triple- 13 C-labeled system are determined and compared with carbon-proton and/or proton-proton coupling constants in geometrically similar compounds. Third, the effect of changes in hybridization on long-range carbon-carbon coupling constants is determined for the following three groups of molecules: olefins and saturated hydrocarbons, aliphatic carboxylic acids, and aromatic compounds. In all cases only closely related systems are compared in order to identify the effect of individual molecular parameters. Most importantly, the results indicate that carbon-carbon couplings do correlate in magnitude and sign with carbon-proton and proton-proton couplings in analogous molecular. frameworks. Thus, the coupling mechanisms are similar in all three types of coupling. In addition, the observed trends in long-range carbon-carbon couplings provide an unambiguous method for assigning carbon chemical shifts.

No / Three new C-bonded cyclotriphosphazenes, [N3P3(2-thienyl)6], 2, [N3P3(3-thienyl)6], 4, and [N3P3(3,3-bithienyl-2,2-ylene)3], 6, have been prepared by two new synthetic procedures and are the first examples of non-spiro and trispirocyclotriphosphazene derivatives composed of thiophene and 3,3-dithiophene substituents, respectively. Their 1H, 13C and 31P NMR parameters are given. The solid state structures of 2, 4 and 6 have been determined by X-ray crystallography.