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Electron diffraction and microwave studies of hionyl tetrafluoride (SOF₄) have been conducted in order to determine its molecular structure. The results from these investigations were however found to be inconsistent. In view of these controversial findings, a microwave investigation was undertaken to accurately assign the rotational transitions, compare the determined moments with those from prior studies and examine the Stark effect in SOF₄ in order to determine its dipole moment. Calculations using an Asymmetric Rotor program were made to determine the Stark coefficients for transitions having J = 1-40 and frequencies between 12-27 MHz. Absorption peaks were identified as had been predicted by theoretical calculations. The spectrum was very rich and exhibited many strong Q-branch transitions (ΔJ=0). Most were high J transitions whose Stark components could not be resolved. The R-branch transitions (ΔJ=1), were observable for only low J transitions and at very low Stark voltages. Stark peaks were not well resolved for the low J transitions; most of them had been masked by the strong Q-branch transitions. Data from the 1(0,1) ----> 2(1,1) transition at 14049 MHz gave a dipole moment of 0.97 Debye. A least squares fit of the observed frequencies correlated well with those from the structure D4, proposed by Hedberg and Hedberg. The rotational constants and moments of inertia were calculated to obtain the values: A = 4181.0 ± 0.04 MHz B = 3289.8 ± 0.04 MHz C = 3206.3 ± 0.04 MHz I_a= 120.9 ± 0.02 amu Ų I_b= 153.6 ± 0.02 amu Ų I_c= 157.6 ± 0.02 amu Ų / Master of Science

A prevalência da erosão dental tem aumentado dentre diversas populações e tratamentos capazes de prevenir o desenvolvimento ou controlar a progressão das lesões existentes vem sendo investigados. Dados da literatura recente reportam que a utilização de fluoretos para estas finalidades promove resultados positivos, principalmente quando os compostos contém cátions metálicos polivalentes associados ao fluoreto, como é o caso do tetrafluoreto de titânio (TiF4). Entretanto, sua aplicação clínica ainda não é possível, devido à falta da definição de protocolo ideal, que envolvem fatores que podem influenciar a proteção conferida pelo produto à superfície dental. O objetivo desta tese foi contribuir com o estabelecimento de um protocolo eficiente, mesmo sob a ação dos fatores modificadores presentes na cavidade bucal. Este trabalho apresenta um compilado de cinco estudos laboratoriais, apresentados na forma de capítulos. Nos estudos in vitro, foram utilizadas amostras de dentina radicular humana para avaliar os efeitos causados pela variação da concentração, veículo e pH dos produtos fluoretados sobre a perda de superfície após ciclagem erosiva. Os resultados nortearam posterior estudo in situ que testou, sob as condições presentes na cavidade bucal, a efetividade do tratamento no controle da erosão. Adicionalmente, determinou-se o grau de oclusão tubular gerado pela aplicação do gel de TiF4. Concluiu-se que composições contendo alta concentração de TiF4, em seu pH original e em veículos de mais alta substantividade, permitem significativa redução do processo de erosão, tendo sido capazes de desacelerar a progressão das lesões. Além disso, a camada ácidoresistente formada sobre a superfície dental se mantém após severa ciclagem erosiva/abrasiva e pode promover efeitos adicionais como a obliteração parcial da entrada dos túbulos dentinários. / The prevalence of dental erosion has increased among several populations and treatments capable of preventing the development or controlling the progression of existing lesions have been investigated. Recent literature data report that the use of fluoride for these purposes promotes positive results, especially when the compounds contain polyvalent metal cations associated with fluoride, such as titanium tetrafluoride (TiF4). However, its clinical application is not yet possible, due to the lack of definition of an ideal protocol, which involves factors that may influence the protection achieved by the product on the dental surface. The aim of this thesis was to contribute to the establishment of an efficient protocol, even under the action of modifying factors present in the oral cavity. This paper presents a compilation of five laboratorial studies, presented in the form of chapters. In the in vitro studies, human root dentin samples were used to evaluate the effects caused by the variation of concentration, excipient and pH of the fluoride products on the surface loss after erosive cycling. The results guided a subsequent in situ study which tested, under the conditions present in the oral cavity, the treatment effectiveness on the erosion control. Additionally, the degree of tubular occlusion generated by TiF4 gel application was determined. It was concluded that compositions containing a high concentration of TiF4, in their original pH and in excipients with higher substantivity, allow a significant reduction of the erosion process, being able to decelerate the lesions progression. Besides, the acid-resistant layer formed on the dental surface remains after severe erosive/abrasive cycling and may promote additional effects, such as partial obliteration of the dentinal tubules entrances.

Thesis (Sc. D.)--University of Michigan, 1960. / Abstracted in Dissertation abstracts, v. 21 (1960) no. 8, p. 2220. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

A prevalência da erosão dental tem aumentado dentre diversas populações e tratamentos capazes de prevenir o desenvolvimento ou controlar a progressão das lesões existentes vem sendo investigados. Dados da literatura recente reportam que a utilização de fluoretos para estas finalidades promove resultados positivos, principalmente quando os compostos contém cátions metálicos polivalentes associados ao fluoreto, como é o caso do tetrafluoreto de titânio (TiF4). Entretanto, sua aplicação clínica ainda não é possível, devido à falta da definição de protocolo ideal, que envolvem fatores que podem influenciar a proteção conferida pelo produto à superfície dental. O objetivo desta tese foi contribuir com o estabelecimento de um protocolo eficiente, mesmo sob a ação dos fatores modificadores presentes na cavidade bucal. Este trabalho apresenta um compilado de cinco estudos laboratoriais, apresentados na forma de capítulos. Nos estudos in vitro, foram utilizadas amostras de dentina radicular humana para avaliar os efeitos causados pela variação da concentração, veículo e pH dos produtos fluoretados sobre a perda de superfície após ciclagem erosiva. Os resultados nortearam posterior estudo in situ que testou, sob as condições presentes na cavidade bucal, a efetividade do tratamento no controle da erosão. Adicionalmente, determinou-se o grau de oclusão tubular gerado pela aplicação do gel de TiF4. Concluiu-se que composições contendo alta concentração de TiF4, em seu pH original e em veículos de mais alta substantividade, permitem significativa redução do processo de erosão, tendo sido capazes de desacelerar a progressão das lesões. Além disso, a camada ácidoresistente formada sobre a superfície dental se mantém após severa ciclagem erosiva/abrasiva e pode promover efeitos adicionais como a obliteração parcial da entrada dos túbulos dentinários. / The prevalence of dental erosion has increased among several populations and treatments capable of preventing the development or controlling the progression of existing lesions have been investigated. Recent literature data report that the use of fluoride for these purposes promotes positive results, especially when the compounds contain polyvalent metal cations associated with fluoride, such as titanium tetrafluoride (TiF4). However, its clinical application is not yet possible, due to the lack of definition of an ideal protocol, which involves factors that may influence the protection achieved by the product on the dental surface. The aim of this thesis was to contribute to the establishment of an efficient protocol, even under the action of modifying factors present in the oral cavity. This paper presents a compilation of five laboratorial studies, presented in the form of chapters. In the in vitro studies, human root dentin samples were used to evaluate the effects caused by the variation of concentration, excipient and pH of the fluoride products on the surface loss after erosive cycling. The results guided a subsequent in situ study which tested, under the conditions present in the oral cavity, the treatment effectiveness on the erosion control. Additionally, the degree of tubular occlusion generated by TiF4 gel application was determined. It was concluded that compositions containing a high concentration of TiF4, in their original pH and in excipients with higher substantivity, allow a significant reduction of the erosion process, being able to decelerate the lesions progression. Besides, the acid-resistant layer formed on the dental surface remains after severe erosive/abrasive cycling and may promote additional effects, such as partial obliteration of the dentinal tubules entrances.

High resolution solar spectra are routinely recorded since more than two decades by the University of Liège at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with Fourier Transform Infrared (FTIR) spectrometers. Over the last years, major improvements have been implemented in the algorithms used to retrieve the abundances of atmospheric constituents accessible to the FTIR technique. Now, in addition to total column, information on the vertical distribution of the target gas is often available, allowing producing partial column data sets. We take advantage of these improvements to generate and characterize long-term total and partial columns time series of some important inorganic fluorinated trace gases deduced from FTIR measurements performed at Jungfraujoch. First, our investigations on hydrogen fluoride (HF) indicate that the adoption of a Galatry line shape model for this species significantly improves the fitting quality of the retrievals. The sensitivity of our FTIR measurements to HF inversions in three distinct regions that range from the low to the high stratosphere is confirmed thanks to products derived from two satellites and from two numerical models. We further demonstrate that the HF seasonal variations that occur in the low stratosphere are mainly responsible for the seasonal cycle observed in our HF total column time series. We have also developed an original multi-spectrum multi-window retrieval strategy allowing to derive, for the first time, some information on the vertical distribution of carbonyl fluoride (COF2) from ground-based FTIR measurements. After comparison with model data, our COF2 and HF FTIR datasets are combined to assess the atmospheric inorganic fluorine burden Fy. A trend analysis of our HF, COF2 and Fy time series is then performed for four different time periods spanning the 1985-2010 time interval. While we observe a recent stabilization for HF, corresponding COF2 data show a significant rise, after a period of significant reduction in its accumulation rate. This is probably ascribable to the combination of the decrease of its main source gas CFC-12 with the increase of the substitute product HCFC-22. However, this increase in the COF2 rate of change does not significantly impact the Fy trend, which is essentially driven by the change in HF. In addition, we show that the partitioning between the two major fluorine reservoirs HF and COF2 has not changed since the beginning of this century. Together, they account for around 95% of total inorganic fluorine in the atmosphere. Finally, we study the long-term evolution of carbon tetrafluoride (CF4), for the first time from ground-based FTIR measurements. The trend analysis of our time series indicates a slowing, initiated during the nineties, in the CF4 growth rate despite the fact that the absolute loading of this compound is still increasing. Our linear accumulation rates are consistent with those deduced from space or surface measurements.

Trimethyltin fluoride (Me3SnF) is a useful fluorinating agent in organometallic chemistry. Its solid-state structure has been investigated by X-ray crystallography showing a polymeric fluorine-bridged structure. Disorder, however, has precluded the accurate refinement of all structural parameters. In order to obtain accurate structural information, trimethyltin fluoride was investigated using high-resolution 13C, 19F, and 119Sn solid-state NMR spectroscopy using a four-channel HFXY capability. The 119Sn{1H} solid-state NMR spectrum agrees with pentacoordination about Sn in this compound. The high-resolution 119Sn{19F, 1H}, 13C{1H,19F} and 19F{1H} NMR spectra offer unambiguous determination of 1J(119Sn-19F) and 1J(119Sn-13C) coupling constants. Furthermore, the analysis of the 119Sn{19F, 1H}, 119Sn{1H}, and 19F{1H} MAS spectra as a function of spinning speed allowed for the determination of the 119Sn CSA and J anisotropy, as well as the 119Sn-19F dipolar couplings. These were determined via SIMPSON simulations of the 13C, 19F, and 119Sn NMR spectra. Finally the 119Sn{19F, 1H} revealed fine structure as the result of 119Sn-117Sn two bond J-coupling, seen here for the first time. Sulfur tetrafluoride can act as a Lewis acid. Claims had been presented for the formation of an adduct between SF4 and pyridine, but no conclusive characterization had been performed. In the present study, adducts of SF4 with pyridine, lutidine, 4-picoline and triethylamine were prepared and characterized by low-temperature Raman spectroscopy. Sulfur tetrafluoride also acts as a fluoride-ion donor towards strong Lewis acids, such as AsF5 and SbF5, forming SF3 + salts. Variable-temperature (VT) solid-state 19F NMR spectroscopy showed that SF3 +SbF6 – exists in three phases with phase transitions at ca. –45 and –85°C, while SF3 +AsF6 – exists only as one phase between +20 and –150 °C. The phases of SF3 +AsF6 – were also characterized by VT Raman spectroscopy. / xvi, 170 leaves : ill. (some col.) ; 29 cm

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