The Role of Multiple Teaching Strategies in Promoting Active Learning in Organic Chemistry

We have introduced four alternative teaching strategies into our yearlong organic chemistry course and have assessed changes in student performance relative to the same course taught by the same instructors using a more traditional lecture format. These strategies, which include reading worksheets, dialogues, in-class worksheets, and role-playing, allow the professor to move through a learning cycle that may effectively accommodate the students needs and multiple learning styles. The reading worksheets guide students through the concept phase and dialogues help students identify the importance of the concepts as they articulate these ideas for themselves. Group worksheets and role-playing provide opportunities for peer-interaction, application of knowledge, creativity, and self-expression. Others have shown that active learning strategies neither enhance nor diminish a students ability to retain factual information, a finding that is supported by our study. Our data from this one study show, however, that students taught by a more traditional approach demonstrate a greater variation in final exam performance between first and second semesters than those taught using a combination of techniques. This result reflects a shift in emphasis from the professor as an information source to the actively engaged student taking responsibility for his or her own learning. This study suggests that these methods, when used in a consistent fashion in conjunction with interactive lecturing, provide a broad base to facilitate student learning and aid in the development of higher order thinking skills.     

Development of the continuously variable volume reactor for flow injection analysis: Part 1. Design, capabilities and testing

A new apparatus for mixing sample and reagent in flow injection analysis (FIA) is described. The continuously variable volume reactor (CVVR) replaces the conventional mixing coil in a flow injection (FI) manifold to provide mixing and dilution. A linear actuator motor allows control of the chamber volume via LabVIEW software. The chamber volume can be incremented in steps of 1 μl over the range 68-1704 μl. In addition, the chamber has an integral variable-speed stirring unit that is also under computer control. Experiments were performed to evaluate the dispersion characteristics of this new device, evaluate the volume reproducibility, and understand the mixing characteristics. Use of the chamber is shown in the determination of iron(II) in pond water, and in NIST SRM 1643d with excellent results and a detection limit of 3.7 μg/l iron(II). Advantages of the CVVR and future research activities using the device are discussed.     

Can magnetic circular dichroism tackle the problem of site symmetry in solutions?

A new approach to unravel the site symmetry of lanthanides in solutions is presented. The magnetic circular dichroism spectra of Eu³⁺ in the symmetries D_3h, C_4v and D_2d are simulated. In these simulations, the main idea is to introduce the magnetic field along a 3-fold axis, being the resultant of the three equivalent X-, Y- and Z-direction of a cube. This implies that the parallel and perpendicular Zeeman effects are taken into account simultaneously.     

Synthesis of Nickel Supported Catalysts for Hydrogen Production by Sol-Gel Method

SiO₂ and Al₂O₃ supported Ni catalysts were synthesized in the form of xerogels: the SiO₂ based materials were prepared starting from Ni propionate or glycolate salts and reacting them with tetraethoxysilane (TEOS) in propionic acid, Si(ethylene glycolate) or sodium silicate. The Al₂O₃ supported catalysts were prepared similarly from Ni propionate salts with Al iso-propoxide salts. Narrow metal particles and strong metal support interactions are observed in the sol-gel catalysts. The metal dispersion was higher for Al₂O₃ based materials than the SiO₂ ones and it deeply depends on the Ni precursor for the silica supported Ni. Wet impregnated oxides with similar Ni loading have higher metal surface area than those from sol-gel processing. The influence of surface differences on the catalytic activity of the materials was studied following the CH₄ and CO₂ reaction in dry reforming conditions by pulse reaction tests.     

Ab initio stochastic optimization of conformational and many-body degrees of freedom

Moderate to large size molecules in solution have complex energy surfaces due to intramolecular (conformational) and intermolecular (many-body) interactions. The first principles Monte Carlo (FPMC) method, previously shown to effectively locate minimum-energy structures for systems with only many-body complexity, has been extended to address conformational flexibility by adding three new Monte Carlo move types. The primary advantage of the FPMC method is the ability to efficiently locate minimum energy structures of molecules with conformational flexibility in the presence of explicit solvent molecules using highly accurate quantum chemical calculations. The additions to FPMC were validated by studying conformers of glycerol, glyceraldehyde, and a large humic acid monomer unit. The structure of glyceraldehyde in the presence of one and two water molecules was also explored to demonstrate the power of FPMC to study systems with both conformational and many-body degrees of freedom.     

The molecular structure of 2-methylbenzotriazole (2MeBzTr) in connection with the x-ray structure of 2MeBzTr.HBF4.H2O

The fluoroborate of 1H-2-methylbenzotriazolium monohydrate crystallizes in the Pbca space group [Z = 8, a = 16.734(3), b = 19.153(9), c = 6.937(1) Å], The hydrogen bond network between the three molecules, 2MeBzTr, HBF₄ and H₂O, corresponds to a situation intermediate between the fluoroborate of a protonated benzotriazole (BF4^?.2MeBzTrH⁺) and a neutral benzotriazole hydrogen-bonded to fluoroboric acid (HBF₄,2MeBzTr). The behaviour of the title compound in solution is also intermediate between these two extreme situations. Thus, the present compound is one of the rare examples of a proton solvated only by very weak hydrogen bond acceptors.     

Modeling the adsorption of U(VI) onto animal chitin using coupled mass transfer and surface complexation

This paper reports the development of a treatment system, using animal chitin as a passive biosorbent, for removing U(VI) from aqueous waste streams. An integral part of this system is a model that provides for the optimization of the treatment system through simulation of U(VI) removal efficiency based on the characteristics of the influent waste stream. The model accounts for changing solution matrix conditions through the coupling of surface complexation and mass transfer models. Complexation of U(VI) by chitin surface sites was modeled using FITEQL. Application of FITEQL in the “forward” mode provided the sorbed and aqueous phase concentrations needed for the mass transfer model. The mass transfer model was derived for both batch and continuously stirred tank reactor (CSTR) configurations using Fick's Law, reactor mass balances and rate law expressions. The coupled model was successfully validated using CSTR data at pH 6.5 and rate constants determined from batch sorption experiments. The CSTR configuration yields a steady-state, eighty percent U(VI) removal for 1 μM influent U(VI) with a solution-phase pH of 6.5 and 3.9 g l⁻¹ chitin.     

New [g]-fused [1,2,4]triazolo[1,5-c]pyrimidines: Synthesis of pyrido[3,2-e] and [4,3-e][1,2,4]triazolo[1,5-c]pyrimidine,pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine and [1,2,4]triazolo[1,5-c]pteridine derivatives

A number of 2-aryl-substituted pyrido[3,2-e] and [4,3-e][1,2,4]triazolo[1,5-c]pyrimidines and [1,2,4]triazolo[1,5-c]pteridines 11,12a,b,e , their corresponding 5-carbonyl derivatives 7,8a,b,e and some pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidin-5-ones 7,8c,d have been synthesized, according to different pathways. The new tricyclic heterocycles were prepared with the aim of studying their possible benzodiazepine receptors affinity.