利用超瑞利散射，我們能夠得知有機分子的超極化率，從而幫助我們對其在液態時的結構及相互作用加深認識和了解。在此研究項目，我們將通過測量對-硝基苯胺溶劑或硝基苯之稀釋混合物的超瑞利散射退極化比，分別提取當中的相干以及非相干散射訊號，並對分子間互相的位置以及方向相關性進行研究。同時，我們將針對分子間的短程和長程相互作用，利用其分別衍生的局域相干散射與離域相干散射進行深入探討。研究顯示，退極化比會受分子間的平均距離所影響，而實驗中將利用對-硝基苯胺在溶液中的濃度或硝基苯的稀釋率對平均距離進行調整。粗略估算當分子間的相互作用能與熱能的強度可比時，退極化比將會有明顯的變化。研究中我們運用簡單的偶極硬球模型，假設分子間為經典的電偶極子相互勢能，同時只考慮一對分子之間的直接相互作用，並以球直徑作為唯一參數擬合實驗結果。另一方面，通過觀察實驗中違反局域散射的對稱性，我們證實硝基苯分子間存在著長程相關性。而以不同溶劑進行稀釋，例如甲醇和丙酮時，會破壞其長程相關性，但當其與苯類溶劑，如對-二甲苯混合時，則會保持其長程相關性。因此，分子之間的長程相關性曾被認為是來自苯環之間的π-π相互作用。過往曾經有研究提出一項將液體中的集體震動模式以震動子(libron)表示的模型，能夠解釋觀察到的不對稱性，但此模型的擬合結果與此實驗中硝基苯以甲醇稀釋，並將其相關性破壞的結果並不相符。另外，以苯甲醇稀釋的結果與純硝基苯之間的不對稱現象相反，令π-π相互作用的假設受到質疑。直至現在，仍未有一項合理的模型能解釋得到實驗中所觀察到分子間的長程相關性。 / Hyper-Rayleigh Scattering (HRS) can be used to determine the first hy-perpolarizability β and examine the structure of organic compounds in liquid states. In this research project, by studying the HRS depolarization ratios of solutions of para-nitroaniline (PNA) or diluted mixtures of nitrobenzene, coherent and incoherent scattering signals were extracted for investigation of the spatial and angular correlations between molecules in a liquid state. Both the localized coherent light scattering, which is controlled by the strength of short-range intermolecular interaction, and the delocalized coherent scattering, which is related to the long range correlation between molecules, were revealed. The depolarization ratios were found to depend on the intermolecular distance, which varied with the concentration of the PNA in the solution or the dilution ratio of pure nitrobenzene in various solvents. A rough estimation shows that significant depolarization ratio variation should occur when the interactionenergy becomes comparable to the thermal energy. With the pair correlations calculated by a dipolar hard sphere model that assumed a classical dipolar interaction potential, the experimental results can be accounted by the theory using the hard sphere diameter as the only fitting parameter. The long range correlation between molecules was confirmed to exist even in the liquid state of pure nitrobenzene by observing a deviation from the local scattering symmetries. The long range correlation between nitrobenzene molecules was found to be easily destroyed by mixing with various solvents such as methanol and acetone, but was maintained by mixing with p-xylene, which is a solvent with benzene-like molecules. The π-π inter-action between the molecules was proposed to be the origin of the long range correlations. A model of delocalized collective mode (libron) that coexists with localized orientational diffusion mode in the solution was previously introduced to explain the observed phenomena. However, break downof the long range correlation by dilution using methanol showed a disagreement with the fitting of the libron model. Furthermore, use of benzol alcohol as a dilutant gives an opposite effect on the long range correlations of the nitrobenzene molecules, which makes the π-π interaction model for long range correlation between nitrobenzene molecules questionable. Presently, there is no satisfactory model on the long range correlation between molecules that can explain all our experimental results. / Detailed summary in vernacular field only. / Chan, Yan Chun = 有機溶液之相干超瑞利散射研究 / 陳恩進. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 129-132). / Abstracts also in Chinese. / Chan, Yan Chun = You ji rong ye zhi xiang gan chao rui li san she yan jiu / Chen Enjin. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Basic Theory --- p.7 / Chapter 2.1 --- Introduction to nonlinear optics --- p.7 / Chapter 2.2 --- Harmonic generation --- p.10 / Chapter 2.3 --- Nonlinear optical phenomena --- p.12 / Chapter 2.4 --- Frequency dependent susceptibility --- p.13 / Chapter 2.5 --- Classical model to susceptibility --- p.14 / Chapter 2.6 --- Calculation of the Nonlinear Processes using Schrödinger Equation --- p.18 / Chapter 2.7 --- Densitymatrix formulation. --- p.20 / Chapter 2.8 --- Hyper-Rayleigh Scattering (HRS) --- p.23 / Chapter 3 --- Experimental Setup and Procedures --- p.30 / Chapter 3.1 --- Experimental Setup --- p.30 / Chapter 3.2 --- Instruments --- p.32 / Chapter 3.2.1 --- Laser System --- p.32 / Chapter 3.2.2 --- Sample cells --- p.33 / Chapter 3.2.3 --- Camera Lens --- p.34 / Chapter 3.2.4 --- Numerical Aperture --- p.35 / Chapter 3.2.5 --- Monochromator --- p.35 / Chapter 3.2.6 --- Photomultiplier --- p.35 / Chapter 3.2.7 --- Photon counter --- p.36 / Chapter 3.3 --- Experimental procedures --- p.37 / Chapter 3.3.1 --- Sample preparation --- p.37 / Chapter 3.3.2 --- Focus point calibration --- p.37 / Chapter 3.3.3 --- Measurement of depolarized intensities and ratios --- p.41 / Chapter 4 --- Instrumental calibration and error analysis --- p.43 / Chapter 4.1 --- PMT applied voltage and photon counter discrimination level --- p.43 / Chapter 4.2 --- HRS wavelength and spectral width --- p.46 / Chapter 4.3 --- Polarizations --- p.50 / Chapter 4.4 --- Slit width --- p.52 / Chapter 4.5 --- Pulsed laser repetition rate --- p.53 / Chapter 4.6 --- Gate width and gate delay --- p.55 / Chapter 4.7 --- Statistical error --- p.57 / Chapter 4.8 --- Photon counting error --- p.61 / Chapter 4.9 --- Numerical aperture collimation --- p.63 / Chapter 4.10 --- Depolarization ratio bias --- p.65 / Chapter 4.11 --- Laser focusing point deviation --- p.69 / Chapter 5 --- Measurement and results of localized coherent Hyper-Rayleigh scatterings --- p.74 / Chapter 5.1 --- Modeling of localized coherent scattering --- p.76 / Chapter 5.2 --- Localized coherent scattering of PNA --- p.84 / Chapter 5.3 --- Localized coherent scattering of Nitrobenzene --- p.91 / Chapter 5.4 --- Study with absorption spectrum --- p.96 / Chapter 5.5 --- Non-zero hyperpolarizability off-diagonal elements --- p.101 / Chapter 6 --- Study of delocalized coherent Hyper-Rayleigh scattering --- p.105 / Chapter 6.1 --- Delocalized coherent scattering of PNA --- p.106 / Chapter 6.2 --- Delocalized coherent scattering of nitrobenzene --- p.110 / Chapter 6.3 --- Libronmodel --- p.115 / Chapter 6.4 --- Long range correlations of PNAmolecules --- p.118 / Chapter 6.5 --- Ionic contaminations --- p.120 / Chapter 6.6 --- Long range correlations of other liquids --- p.123 / Chapter 7 --- Conclusions --- p.125 / Bibliography --- p.129

This thesis describes the development and implementation of single-molecule carbon nanotube-based field-effect transistors (smFETs) for studies of nucleic acid dynamics. Single-molecule techniques, most notably fluorescence resonance energy transfer (smFRET) and single-molecule force spectroscopy, have been employed to investigate biomolecular dynamics due to their ability to directly observe discrete, rare events, as well as to characterize structural motions in a diverse ensemble. However, these techniques are hampered by difficulties in measuring millisecond-scale dynamics, such as base pair rearrangements, as well as the inability to observe unperturbed individual molecules for long times. Alternatively, smFETs allow observation of the dynamics of charged biomolecules, such as charged amino acids in proteins or the phosphate groups of nucleic acid backbones, with microsecond temporal resolution. Structural rearrangements of a single charged molecule on the surface of a single-walled carbon nanotube (CNT) transistor can lead to measureable fluctuations in conductance through the CNT. Thus, this technique allows for simultaneous characterization of fast events and, due to the label-free and minimally-invasive nature of smFET technology, the quantification of how the frequency of these events change over long time-scales. A portion of this work describes smFET fabrication, focusing on improvements to the functionalization method, a critical step to reliably generate individual attachment sites on the CNT for subsequent single-molecule studies. A new synthetic chemistry approach is performed in ultraminiaturized, nanofabricated reaction chambers; using lithographically-defined nanowells, single-point attachments are achieved on hundreds of individual carbon nanotube transistors, providing robust statistics and unprecedented spatial control in adduct positioning. Each device acts as a sensor to detect, in real-time and through quantized changes in conductance, single-point functionalization of the nanotube, as well as consecutive chemical reactions and subsequent molecular interactions molecular conformational changes. In particular, this thesis is focused on studying the dynamics of nucleic acids using smFET technology. First, the smFET technique presented is verified by studying the thermodynamics and kinetics of DNA hybridization, the results of which compare favorably both with predicted values and previous smFET studies using alternative device architectures. Next, the reversible folding of a single-stranded telomeric DNA sequence known to form a G-quadruplex structure is studied, revealing the characteristic increased stability of the G-quadruplex structure in the presence of potassium ions relative to sodium ions. Finally, smFET studies of the dynamics of the adenine-sensing pbuE riboswitch aptamer found in Bacillus subtilis are discussed. These results demonstrate how long-lived, ligand-dependent intermediates form at a base-pair level and suggest that these intermediates have consequences for riboswitch-regulation by adenine binding to the aptamer. With the increased time resolution of smFET technology, this work has achieved the first observation of RNA zipping and unzipping at the single-molecule level, as well as label-free observations of the effects of a three-way junction motif on helix zipping and unzipping.

In asymmetric catalysis, interactions between multiple molecules of catalyst can be important for achieving high catalyst activity and stereoselectivity. In Chapter 1 of this thesis, we introduce catalyst-catalyst interactions in the context of the classic Kagan nonlinear effect (NLE) experiment, and present examples of the strengths and drawbacks of the NLE experiment. For the remainder of the thesis, we explore catalyst-catalyst interactions in the context of two different reactions. First, in Chapter 2, we apply a combination of reaction kinetics and computational chemistry to a reaction that is well known to require the cooperative action of two molecules of catalyst: the (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides. In our investigation, we demonstrate that stereoselectivity in the HKR is achieved through catalyst-catalyst interactions and provide a model for how high selectivity and broad substrate scope are achieved in this reaction. In Chapter 3, we focus our attention on the thiourea-catalyzed enantioselective alkylation of alpha-chloroethers with silyl ketene acetal nucleophiles, a reaction that was not known to require the cooperative action of two molecules of catalyst at the outset of our investigation. By using a wide range of physical organic chemistry tools, we established that the resting state of the optimal thiourea catalyst is dimeric under typical reaction conditions, and that two molecules of catalyst work cooperatively to activate the alpha-chloroether electrophile. The implications of this mechanism for catalyst design are discussed. / Chemistry and Chemical Biology

Stacking interactions, also known as π-π or face-to-face interactions, occur between molecules whose π bonds are in parallel planes. They are used to design self-assembling structures in nanotechnology, influence organic reactions and are ubiquitous in nature. The stacking interactions of substituted benzene heterodimers and substituted benzene-natural nucleobase heterodimers are examined. Both electron-donating and withdrawing groups are studied by varying their type, number and location around the benzene ring. The studies are done by carrying out systematic scans of the potential energy surface at the MP2/6-31G*(0.25) level of theory. Charge transfer interactions and extent of charge separation in the monomer are found to be dominant when the difference in ESP between the monomers is large and small, respectively. Dipole-dipole interactions are also found to affect stacking interactions. The results from MP2/6-31G*(0.25) are checked against those at the CCSD(T)/CBS limit for select cases and are found to be within 81- 110%. / xii, 166 leaves : ill. ; 29 cm

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22468号 / 工博第4729号 / 新制||工||1739(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 田中 一生, 教授 秋吉 一成, 教授 古賀 毅 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20946号 / 理博第4398号 / 新制||理||1632(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 依光 英樹, 教授 丸岡 啓二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Autoxidation is a radical mediated chain-process that involves initiation, propagation, branching and termination reactions and is responsible for the spontaneous peroxidation of hydrocarbons, formally appearing as RH + O₂ → ROOH. Autoxidation is a consequentially damaging process in many domains, ranging from materials to automotive transportation to biology and medicine. One of the key intermediates in the propagation of autoxidation is the peroxyl radical (ROO•) which can be targeted by radical-trapping antioxidants (RTAs) that promote chain-termination, mitigating the damage of autoxidation. Chapter 1 lays out the fundamental chemistry of both autoxidation and RTAs as well as a history of the rational design of phenol and diarylamine-type RTAs. Lipid-peroxidation (i.e. autoxidation) is a key feature of ferroptosis which is a form of cell death that has been associated with many serious conditions such as ALS, Alzheimer's, Huntington's and Parkinson's disease, and lipid-soluble RTAs such as Vitamin E have been shown to acutely suppress ferroptosis. An aspect of RTA chemistry that has not been well studied/understood hitherto is their kinetic behaviour in phospholipid membranes, and we hypothesized that this would be a very relevant consideration for designing compounds that target lipid-peroxidation and ferroptosis. In Chapter 2 we systematically examine the kinetic behaviour for a series of hindered and unhindered phenolic RTAs in various mediums, particularly in phosphatidylcholine (PC) liposomes. The key chemical interaction in the PC membrane that fundamentally changed the observed kinetics of the phenolic RTAs is a very strong hydrogen-bonding interaction with the phosphate-diester headgroup that suppresses the phenols' ability to trap ROO•, an effect that was previously overlooked. In Chapter 3 we further expanded/validated the model by studying over 40 phenoxazine (PNX) and phenothiazine-based (PTZ) RTAs, which showed the quantitative/predictive capabilities of the H-bonding effect. By introducing a water-soluble co-antioxidant, Vitamin C (ascorbate), we were able to study many features of the PNX/PTZ radical intermediates with respect to their reactivity and dynamics. The PNX/PTZ were far more persistent than the Vitamin E analogue 2,2,5,7,8-pentamethyl-6-chromanol (PMC), meaning that they catalytically trapped lipid-peroxyls far more efficiently (i.e., higher turnover number). Additionally, there is strong evidence suggesting that the PNX/ascorbate synergism is a diffusion-controlled process. The study was further expanded to biological models. Ferroptosis in vitro was inhibited by every single one of these compounds, and there was a general positive correlation between RTA kinetics (kᵢₙₕ) and ferroptosis rescue potency (EC₅₀) as well as a positive correlation between lipophilicity (logP) and ferroptosis rescue potency. A lead PNX compound, 3-trifluoromethyl-8-tert-butylphenoxazine, was identified in this study on the basis of superior potency and metabolic stability. When used to treat mice with GPx4 deletion in kidneys, an in vivo model of ferroptosis, it was found to extend the life of the mice in a statistically significant fashion compared to the vehicle control. In Chapter 4 there is further elaboration on the dynamics of PNX/ascorbate synergy and a demonstration of the early works toward developing a drug-like-PNX ferroptosis inhibitor, based on the conclusions from the work in Chapter 3. In Chapters 5 and 6 the research is focused on the development novel RTAs for the application of inhibiting autoxidation in lubricants in high temperature environments. Heavy machinery and most transportation technologies require lubrication to aid safe and efficient movement, and these lubricants/greases are highly susceptible to autoxidation. Large quantities of RTA additives are expended to extend the service life of these materials and there is a constant appetite for innovation to find new and improved RTAs for improved economics and competitiveness. In Chapter 5 the behaviour of PNX and PTZ in a simulated high temperature lubricant autoxidations are analyzed, revealing that PNX is highly susceptible to direct O₂-mediated oxidation due to its rapid electron-transfer kinetics, while PTZ is far more resilient despite both compounds having nearly identical oxidation potentials. In Chapter 6, in this same context, previously unreported substituent effects are analyzed which significantly enhance the period of inhibition (tᵢₙₕ) for PTZ compounds. Particular alkyl substituents on the PTZ can increase the number of chains-trapped at high temperatures by fortuitous substituent oxidation that promotes termination, substantially improving their atom-economy. These findings prompt a broader critique of putative catalytic RTA mechanisms which have been taken for granted for nearly three decades.

A presente Dissertação relata a síntese e o estudo conformacional das α-fenilseleno-α-dietóxifosforilacetofenonas para-substituídas p-X-Φ-C(O)CH[SeΦ][P(O)(OEt2] (X=OMe 1, Me 2, H 3, F 4, Cl 5, Br 6 e NO2 7) através da banda de estiramento da carbonila no infravermelho, em solventes de polaridade crescente apoiado por cálculos ab initio HF/6-3IG**. A comparação entre a freqüência e a intensidade relativa dos componentes do dubleto, para os derivados 6 e 7, e do singleto para os derivados 1-5, no solvente apolar tetracloreto de carbono, e dos componentes do dubleto, nos solventes de polaridade crescente (clorofórmio, diclorometano e acetonitrila), para os derivados 1-7, com os dados do cálculo ab initio de 3 (composto de referência), indicou que ambas as conformações estáveis (g1 e g2) apresentam a ligação C-Se na geometria anti-clinal (gauche) em relação à carbonila (C=O), enquanto que a ligação C-P assume uma geometria sin-periplanar (cis) em relação à carbonila. A análise dos contatos interatômicos de átomos relevante em comparação com a soma de seus raios de van der Waals, indicou que ambas as conformações g1 e g2 são fortemente estabilizadas pelo sinergismo das interações orbitalares e eletrostáticas π*(CO) / nSe e Oδ-[CO].....Pδ+[PO]. Analogamente, as interações mais fracas Oδ-[OR]..... Cδ+[CO], 0-Hδ+[SeΦ]....Oδ-[PO] e 0-Hδ+[ΦC(O)]....Oδ-[CO] estabilizam as conformações g1 e g2, aproximadamente na mesma extensão. No entanto, somente a conformação g1 é estabilizada pela interação eletrostática (ligação de hidrogênio) Hδ+[α-CH].....Oδ-[OR], enquanto que sómente a conformação g2 é desestabilizada pelo Efeito de Campo Repulsivo entre os dipolos Cδ+=.Oδ- e Pδ+-ORδ- Assim sendo, pode-se concluir que no dubleto de VCO no IV, o componente de maior freqüência e de menor intensidade corresponde à conformação menos estável g2 (do cálculo) enquanto que o componente de menor freqüência e mais intenso corresponde à conformação mais estável g1 (do cálculo). Estes dados estão de pleno acordo com os deslocamentos de freqüência mais negativos da carbonila (ΔVCO) do confôrmero mais estável g1 em relação ao menos estável g2. / This thesis reports the synthesis and the conformational study of some para-substituted α-phenylseleno-α-diethoxyphosphoryl-acetophenones p-X-Φ-C(O)CH[SeΦ][P(O)(OEt)2] (X=OMe 1, Me 2, H 3, F 4, Cl 5, Br 6 e NO2 7) through the analysis of the carbonyl stretching IR band, in solvents of increasing polarity, supported by ab initio HF/631G** computations of 3 (parent compound). The comparison between the frequency and the relative intensity of the doublet components for derivatives 6 and 7, and of the singlet for derivatives 1-5, in non polar solvent, carbon tetrachloride, and of the doublet components, in solvents of increasing polarity (chloroform, dichloromethane and acetonitrile), for derivatives 1-7, with the ab initio data for 3, has indicated that both stable conformations (g1 and g2 ) display the C-Se bond in an anti-clynal (gauche) geometry with respect to the carbonyl (C=O) bond, while the C-P bond assumes a syn-periplanar (cis) geometry relative to the carbonyl group. The analysis of the interatomic contacts between some relevant atoms in comparison with the sum of their van der Waals radii has shown that both g1 and g2 conformations are strongly stabilized almost to the same extension by the synergism of the π*(CO) / nSe and Oδ-[CO] .....Pδ+[PO] orbital and electrostatic interactions. Similarly, the weaker Oδ-[OR] ..... Cδ+[CO], o-Hδ+[SeΦ] ....Oδ-[PO] and o-Hδ+[ΦC(O)] ....Oδ-[CO] interactions stabilise the referred conformations almost to the same extent. However, conformer g1 only is stabilised by the electrostatic interaction (hydrogen bond) ) Hδ+[α-CH] ....Oδ-[OR], while the conformer g2 is the only one which is significantly destabilised through the Repulsive Field Effect which takes place between the Cδ+=Oδ- and Pδ+-ORδ- dipoles. Therefore it may be concluded that the less intense higher vco frequency doublet component should correspond to the less stable g2 conformation, while the more intense lower VCO frequency doublet component should be related to the more stable g1 conformation. Further support for these trends are given by the larger negative carbonyl frequency shifts (ΔVCO) for the g1 conformer relative to the g2 one, for the whole series.

A primeira parte deste trabalho relata o estudo conformacional e das interações eletrônicas das α-dietoxifosforilacetofenonas-para-substituídas Y-Φ-C(O)CH2P(O)(OEt)2 (I), sendo Y= MeO, Me, H, Cl, Br, CN e NO2. Este estudo foi realizado através das espectroscopias no infravermelho, Ressonância Magnética Nuclear de 13C e 31P, apoiados por cálculos ab-initio 6-31G**. A existência de uma única banda simétrica da carbonila, tanto na transição fundamental como no 1° harmônico, conjuntamente com a constatação da ocorrência de uma única conformação de baixa energia através dos cálculos ab-initio, sugerem fortemente a existência na série estudada de um único confôrmero gauche. Os deslocamentos de frequência da carbonila do confôrmero gauche da série (I) mostraram-se negativos e aumentam significativamente em valor absoluto indo-se em para de grupos doadores a aceptores de elétrons. Contrariamente, a frequência de estiramento do grupo fosforila vPO diminui progressivamente no mesmo sentido. Este comportamento foi atribuído à ocorrência simultânea no confôrmero gauche da série (I) tanto da interação eletrostática como da transferência de carga entre o oxigênio do grupo fosforila (carregado negativamente) e o carbono carbonílico (carregado positivamente). Os estudos de Ressonância Magnética Nuclear de 13C mostraram uma constância nos deslocamentos químicos do carbono carbonílico na série (I), bem como uma expressiva blindagem do carbono carbonílico desses compostos em relação às acetofenonas correspondentes de referência. Já os deslocamentos químicos de 31P mostraram-se praticamente constantes ao longo da série estudada. Os dados de Ressonância Magnética Nuclear de 13C foram interpretados como sendo devido à ação simultânea tanto do efeito I do grupo dietoxifosforila como da transferência de carga do oxigênio do grupo fosforila ao carbono carbonílico que se encontram na relação espacial γ gauche. Os espectros no ultravioleta dos compostos da série (I) apresentam uma quase invariabilidade da energia da transição no → π* CO em relação às acetofenonas de referência correspondentes, com exceção dos compostos contendo em para substituintes fortemente atraentes de elétrons, onde ocorre uma discreta hipsocromia da transição no → π* CO. Este comportamento foi interpretado como sendo decorrente tanto da interação hiperconjugativa entre os orbitais π* CO e σ* C-P como também da interação de transferência de carga nO(PO) → π* CO, que é mais pronunciada quando o grupo fenacila dos compostos (I) contém grupos fortemente atraente de elétrons na posição para. A segunda parte da presente Dissertação relata o estudo das reações das α-halogenoacetofenonas-para-substituídas Y-Φ-C(O)CH2Hal com trietilfosfito em benzeno anidro à temperatura de refluxo de benzeno. Nessas condições observou-se a formação das α-dietoxifosforilacetofenonas-para-substituídas Y-Φ-C(O)CH2P(O)(OEt)2 (I) e dos enolfosfatos correspondentes CH2=C[Φ-Y][P(O)(OEt)2] (II), havendo mudança na proporção dos isômeros obtidos à medida que se varia tanto o substituinte na posição para do anel benzênico como a natureza do halogênio na posição α. O substituintes doadores de elétrons levam a formação preferencial dos cetofosfonatos (reação de Michael-Arbuzov) enquanto que substituintes aceptores de elétrons levam a formação preferencial de enolfosfatos (produto da reação de Perkow). Estes dados sugerem que a adição nucleofílica à carbonila com a formação dos enolfosfatos depende da afinidade eletrônica do orbital π* CO que estabiliza em maior ou menor extensão o estado de transição (III) que é o provável passo determinante da reação de Perkow. Assim sendo, no caso do para-nitro derivado que contém o LUMO (principalmente π* CO) de mais baixa energia ocorre a formação preferencial de enolfosfato, enquanto que o para-metoxi derivado onde o LUMO é desestabilizado ocorre formação preferencial do cetofosfonato. As proporções isoméricas de cetofosfonato e enolfosfato obtidos encontram-se linearmente correlacionadas com o σP de Hammet. O presente estudo evidenciou o efeito da natureza do grupo de partida (halogênio α à carbonila) na formação de enolfosfatos e cetofosfonatos nas reações estudadas, i.e constatou-se que quanto melhor for o grupo de partida para um mesmo substituinte na posição i>para das α-haloacetofenonas, maior é a proporção de enolfosfato formado em detrimento do cetofosfonato. O conjunto de dados acima descritos está de pleno acordo com a proposta mecanística de que o estado de transição (III) é o passo determinante da formação dos enolfosfatos na reação de α-haloacetofenonas-para-substituídas com trietilfosfito e praticamente exclui a possibilidade de outras propostas mecanísticas descritas na literatura. / The first part of this work reports the conformational and electronic interaction studies of some α-diethoxyphosphoryl-para-substituted acetophenones Y-Φ-C(O)CH2P(O)(OEt)2 (I), where Y= MeO, Me, H, Cl, Br, CN and NO2. This study was performed by means of infrared, 13C and 31P Nuclear Magnetic Resonance spectroscopies supported by 6-31G** ab-initio computations. The single symmetrical IR carbonyl band observed both in the fundamental and in the first overtone regions along with the existence of a unique low energy conformation obtained by ab-initio calculations, strongly suggest that a single gauche conformer should be present in the whole series (I). The carbonyl frequency shifts for the gauche rotamers of the title compounds are negative and their absolute values increase progressively on going in para position from electron-donating to electron-accepting substituents. Contrarily, the phosphoryl stretching frequencies (vPO) decrease progressively in the same direction. These trends have been ascribed to the simultaneous occurrence of the attractive electrostatic and charge transfer interactions, which take place between the negatively charged phosphoryl oxygen and the positively charged carbonyl carbon atoms in the gauche rotamer of the title compounds. The 13C NMR data showed that the carbonyl carbono chemical shifts are practically constant along the whole series (I) and that these values are significantly upfield shifted with respect to those of the corresponding parent acetophenones. This behavior has been attributed to the simultaneous occurrence of the I effect of the α-diethoxyphosphoryl group along with the charge transfer which occur between the P=O and the C=O groups which are in the γ-gauche geometry. Furthemore, the 31P chemical shifts are almost constant along the series (I). The ultraviolet spectra of the α-diethoxyphosphorylacetophenones (I) present almost the same π* CO transition energies with respect to the same transition in the corresponding acetophenones, excepting the case of the title compounds which bear at the para position strong electron-attracting groups (nitro and cyano) for which a discrete hypsochromic effect of the π* CO transition has been observed. This behavior was ascribed on the grounds of the simultaneous occurrence of the hyperconjugative interaction (IIa) and their corresponding mono- (IIb) and di- (IIc) oxygenated derivatives Y-PhC(O)CH[SOnMe][P(O)(OEt2)] [II, n=0 (a), n=1 (b)] and n=2 (c)]; c) α-bromo, α- ethylsulfonyl-para-substituted acetophenones Y-PhC(O)[Br][SO2Et] III. This study was performed by means of Infrared, Nuclear Magnetic Resonance, Ultraviolet spectroscopies, ab initio computations and X-ray diffraction analysis. For the α-ethylsulfinylacetophenones (Ia) the cis conformer predominates over the gauche one while in the case of the α-ethylsulfonylacetophenones (Ib) the gauche conformer is the more stable relative to the quasi-cis one. The α-methylthio-α-diethoxyphosphoryl acetophenones (IIa) present only a single stable conformer which bears the (SMe) group in a syn-clinal (gauche) geometry and the [P(O)(OEt2)] group in the quasi-periplanar (quasi-cis) geometry with respect to the carbonyl group. The α-methylsulfinyl-α-diethoxyphosphoryl acetophenones (IIb) display two stable conformations corresponding each one to a different diastereomer. The most stable conformer CSSS presents the methylsulfinyl group [MeS(O)] in a quasi-periplanar (quasi-cis) geometry and the diethoxyphosphoryl group [P(O)(OEt2)] in a anti-clinal (gauche) geometry relative to the carbonyl group. The second less stable conformer corresponds to the CRSS diastereomer and displays both the [MeS(O)] and the [P(O)(OEt2)] groups in a syn-clinal (gauche) geometry. The α-methylsulfonyl-α-diethoxyphosphoryl acetophenones (IIc) presents only a single stable conformer bearing both the [MeSO2] and [P(O)(OEt)2] groups in a sin-clinal geometry with respect to the carbonyl group. The α-bromo-α-ethylsulfonylacetophenones III present a single stable conformation bearing the the [SO2Et] group in a syn-periplanar (quasi-cis) geometry and the [Br] atom in a syn-clinal (gauche) geometry relative to the carbonyl group.