The importance of hydrogen bonding in the alkylation of phenols

Hydrogen bond assisted alkylation of phenols is compared with the classical base assisted reactions. The influence of solvents on the fluoride assisted reactions is discussed,· with emphasis on the localization of hydrogen bond charge density. Polar aprotic solvents such as DMF favour a-alkylation, and nonpolar aprotic solvents such as toluene favourC-alkylation of phenol. For more reactive and soluble fluorides, such as tetrabu~ylammoniumfluoride, the polar aprotic solvent favours a-alkylation and nonpolar aprotic solvent favours fluorination. Freeze-dried potassium fluoride is a better catalytic agent in hydrogen bond assisted alkylation reactions of phenol than the oven-dried fluoride. The presence of water in the alkylation reactions reduces the expected yield drastically. The tolerance of the reaction to water has also been studied. The use ofa phase transfer catalyst such as tetrabutylammonium bromide in the alkylation reactions of phenol in the presence of potassium fluoride is very effective under anhydrous conditions. Sterically hindered phenols such as 2,6-ditertiarybutyl-4-methyl phenol could not be alkylated even by using the more reactive fluorides, such as tetrabutylammonium fluoride in either polar or nonpolar aprotic solvents. Attempts were also made to alkylate phenols in the presence of triphenylphosphine oxide.

Dietary Strategies to Optimize Wound Healing after Periodontal and Dental Implant Surgery: An Evidence-Based Review

Methods to optimize healing through dietary strategies present an attractive option for patients, such that healing from delicate oral surgeries occurs as optimally as possible with minimal patient-meditated complications through improper food choices. This review discusses findings from studies that have investigated the role of diet, either whole foods or individual dietary components, on periodontal health and their potential role in wound healing after periodontal surgery. To date, research in this area has largely focused on foods or individual dietary components that may attenuate inflammation or oxidant stress, or foster de novo bone formation. These studies suggest that a wide variety of dietary components, including macronutrients and micronutrients, are integral for optimal periodontal health and have the potential to accelerate oral wound healing after periodontal procedures. Moreover, this review provides guidance regarding dietary considerations that may help a patient achieve the best possible outcome after a periodontal procedure.

Exploring Capacity Building of Ontario Dental Hygiene Educators During National Curriculum Reform

In times of educational change, educators are given the task of implementing new initiatives that meet the needs of a changing environment; yet, they are often dismissed from developmental phases of the reform. This top-down structure deters educators’ personal capacity building as their knowledge, values, assumptions, and beliefs are not acknowledged or explicitly developed as part of the initiative. This study explored Ontario dental hygiene educators’ perspectives of how they may build personal capacity during an externally mandated national curriculum reform, the Entry-to-Practice Competencies and Standards for Canadian Dental Hygienists (National Competencies). Narratives were collected from 5 dental hygiene educators of diverse educational training and teaching organizations. Three themes emerged that included perceptions of structural influence, perceptions of learning access, and perceptions of identity. Each theme was linked to tasks that were required to build personal capacity for sustainable school change. The theoretical framework and the required tasks demonstrated the interconnectedness between educators, leaders, and the organization for building educators’ personal capacity.

Mirroring Enzymes: The Role of H-Bonding In HQuin-BAM Catalyzed Asymmetric Aza-Henry Reactions: A DFT Study into the Reactivity, Mechanism, and Origins of Selectivity

The exact mechanistic understanding of various organocatalytic systems in asymmetric reactions such as Henry and aza-Henry transformations is important for developing and designing new synthetic organocatalysts. The focus of this dissertation will be on the use of density functional theory (DFT) for studying the asymmetric aza-Henry reaction. The first part of the thesis is a detailed mechanistic investigation of a poorly understood chiral bis(amidine) (BAM) Brønsted acid catalyzed aza-Henry reaction between nitromethane and N-Boc phenylaldimine. The catalyst, in addition to acting as a Brønsted base, serves to simultaneously activate both the electrophile and the nucleophile through dual H-bonding during C-C bond formation and is thus essential for both reaction rate and selectivity. Analysis of the H-bonding interactions revealed that there was a strong preference for the formation of a homonuclear positive charge-assisted H-bond, which in turn governed the relative orientation of substrate binding. Attracted by this well-defined mechanistic investigation, the other important aspect of my PhD research addressed a detailed theoretical analysis accounting for the observed selectivity in diastereoselective versions of this reaction. A detailed inspection of the stereodetermining C-C bond forming transition states for monoalkylated nitronate addition to a range of electronically different aldimines, revealed that the origins of stereoselectivity were controlled by a delicate balance of different factors such as steric, orbital interactions, and the extent of distortion in the catalyst and substrates. The structural analysis of different substituted transition states established an interesting dependency on matching the shape and size of the catalyst (host molecule) and substrates (guest molecules) upon binding, both being key factors governing selectivity, in essence, offering an analogy to positive cooperative binding effect of catalytic enzymes and substrates in Nature. In addition, both intra-molecular (intra-host) and inter-molecular (host-guest, guest-guest) stabilizing interactions play a key role to the high π-facial selectivity. The application of dispersion-corrected functionals (i.e., ωB97X-D and B3LYP-D3) was essential for accurately modeling these stabilizing interactions, indicating the importance of dispersion effects in enantioselectivity. As a brief prelude to more extensive future studies, the influence of a triflate counterion on both reactivity and selectivity in this reaction was also addressed.

Prevalencia de caries dental y parodontopatías según estratificación socioeconómica de la población escolar del Municipio de Cienega de Flores, N. L. \f 1982.

Tesis (Maestría en Salud Pública, Especialidad en Odontología Social) UANL

Contenido de fluoruros en el agua de consumo y sus efectos en el tejido dental : San Luis Potosí, México, 1988

Tesis (Maestría en Salud Pública con Especialidad en Odontología Social) UANL

Caries dental y diabetes mellitus no insulino dependiente

Tesis (Maestría en Salud Pública con Especialidad en Odontología Social) UANL.

La participación de los factores externos en el efecto preventivo de la fluoruración o el agua de consumo domestico en la caries dental

Tesis (Maestría en Salud Pública con Esp. en Odontología Social) U.A.N.L.

Diseño de un monitoreo de la dispersión de rayos X en radiografía dental

Tesis (Maestro en Ciencias con especialidad en Metrología de la Radiación) U.A.N.L.

Análisis de la dispersión de rayos-X en el aire en radiografía dental [por] Guillermo Escobedo Valle

Tesis (Maestría en Ciencias con Especialidad en Metrología de la Radiación) U.A.N.L.

Eficacia de las medidas preventivas para caries dental

Tesis (Maestría en Salud Pública con Especialidad en Odontología Social) U.A.N.L.

Prevalencia de caries dental en niños de edad preescolar. Estudio comparativo realizado en las ciudades de Monterrey y Apodaca, N.L.

Tesis ( Maestría en Ciencias Odontológicas con Especialidad en Odontología Infantil) U.A.N.L.

Medición de la longitud de arco dental y su relación con el género y edad en niños de 3 a 6 años que acuden al Posgrado de Odontopediatría de la UANL.

Tesis (Maestría en Ciencias Odontológicas con Especialidad en Odontopediatría) UANL, 2010.

Prevalencia de caries dental en preescolares de tres estratos socioeconómicos.

Tesis (Maestría en Ciencias con Especialidad en Odontología Infantil) UANL, 2010.

Separación padre-hijo : elección de los padres durante la atención dental en la Clínica de Posgrado de Odontopediatría de la UANL.

Tesis (Maestría en Ciencias Odontológicas con Especialidad en Odontopediatría) UANL, 2011.