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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

I. Kinetic and Computational Modeling Studies of Dimethyldioxirane Epoxidations II. Adressing Misconceptions About Energy Changes in Chemical Reactions Through Hands-on Activities

McTush-Camp, Davita 11 May 2015 (has links)
Kinetic studies determining the second order rate constants for the monoepoxidation of cyclic dienes, 1,3-cyclohexadiene and 1,3-cyclooctadiene, and the epoxidation of cis-/trans-2-hexenes by dimethyldioxirane (DMDO) were carried out using UV methodology. Consistent with published results, the kinetics of cis-/trans-2-hexenes by DMDO showed greater reactivity of the cis-isomer compared to that of the trans-compound. Molecular modeling studies for the epoxidation of a series of cis-/trans-alkenes, by DMDO were carried out using the DFT approach. The mechanism of epoxidation by DMDO was modeled by determining the transition state geometry and calculating the electronic activation energies and relative reactivities. The calculations were consistent with a concerted, electrophilic, exothermic process with a spiro-transition state for all cases. Kinetic studies for the monoepoxidation of the cyclic dienes showed a greater reactivity for 1,3-cyclohexadiene compared to that for 1,3-cyclooctadiene. The DFT method was employed to successfully model the transition state for the monoepoxidation of the cyclic dienes by DMDO and successfully predict the relative reactivities. Student misconceptions, at the high school and/or middle school level involving energy changes and chemical reactions have been prevalently noted in literature (by ACS and AAAS). Two examples of these misconceptions are: 1) heat is always needed to initiate a chemical reaction and 2) all chemical reactions create or destroy energy. In order to address these types of misconceptions, an educational module detailing the influence of energy changes on chemical reactions has been developed in conjunction with the Bio-bus program for middle and high school students. Visual aids and hands-on activities were developed in the module to potentially help students overcome/deal with the common misconceptions. Surveys were designed to access the situations (determine the extent of the misconceptions) and the effectiveness of the educational module, before and immediately after the module and one-month later to determine retention. The educational module has been presented to approximately 100 high school students from underrepresented communities. Pre-survey data confirmed the presence of the common misconceptions reported in the literature. Data from the post-survey indicated the new instructional module enhanced the student’s interest of science and expanded their content knowledge and laboratory skills. The post-survey data (immediately following the module) showed a significant difference in two out of five misconceptions when compared to the pre-survey data. However, this significance decreased when the 1-month post-survey data were compared to the pre-survey data.
2

"You get what you pay for" vs "You can alchemize": Investigating Discovery Research Experiences in Inorganic Chemistry/Chemistry Education via an Undergraduate Instructional Laboratory

Bodenstedt, Kurt Wallace 08 1900 (has links)
Synthesis of d10 complexes of monovalent coinage metals, copper(I) and gold(I), with dithiophosphinate/diphosphine ligands -- along with their targeted characterization and screening for inorganic or organic light emitting diodes (LEDs or OLEDs, respectively) -- represents the main scope of this dissertation's scientific contribution in inorganic and materials chemistry. Photophysical studies were undertaken to quantify the phosphorescence properties of the materials in the functional forms required for LEDs or OLEDs. Computational studies were done to gain insights into the assignment of the phosphorescent emission peaks observed. The gold(I) dinuclear complexes studied would be candidates of OLED/LED devices due to room temperature phosphorescence, visible absorption/excitation bands, and low single-digit lifetimes -- which would promote higher quantum yield at higher voltages in devices with concomitant lower roll-off efficiency. The copper(I) complexes were not suited to the OLED/LED applications but can be used for thermosensing materials. Crystallographic studies were carried to elucidate coefficients of thermal expansion of the crystal unit cell for additional usage in materials applications besides optoelectronic devices. This has uncovered yet another unplanned potential application for both copper(I) and gold(I) complexes herein, as both types have been found to surpass the literature's threshold for "colossal" thermal expansion coefficients. Two other investigations represent contribution to the field of chemistry education have also been accounted for in this dissertation. First, a 12-week advanced research discovery experiment for inorganic chemistry has been designed to help students develop application-based content expertise, as well as to introduce students to research experiences that are similar to those found in academia, industry, and government research laboratories. Students are expected to develop a novel research project through conducting a literature search to find suitable reaction protocols, incorporating synthetic techniques, collecting data, characterizing products and applications of those products, and presenting their results. This multi-week research discovery experiment is centered on applications of inorganic synthetic techniques to design, analyze, and screen d10 coinage metal complexes for possible LED/OLED-based applications that were presented in chapter 3 of the dissertation. The second chemistry education contribution pertains to designing a pilot research study to investigate undergraduate chemistry majors' perceptions of environmental sources/influences, self-efficacy, outcome expectations, career interests, and career choice goals in the lab designed in chapter 4 of the dissertation. Specifically, this research aims to gauge students' perceptions of their ability to perform synthetic and analytical methods for the creation of materials that were used in a novel research experiment in the context of an inorganic chemistry laboratory. This research study used a survey to collect data on students' motivation, self-efficacy, career interests, and career goals upon graduation, along with their perceived barriers within the course. This research study is guided by the following research question: How does an inorganic chemistry laboratory course, following a research discovery model, impact undergraduate students' (a) confidence with techniques and skills, (b) perception of ability to conduct research, and (c) interest in pursuing careers involving chemistry?

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