Achieving greater feedback and flexibility using online pre-laboratory exercises with non-major chemistry students

Compulsory online pre-laboratory exercises were required of non-major, first-year university chemistry students in response to poor student preparation for laboratory sessions. The online pre-laboratory exercises were designed to be straightforward, endeavoring to help students maximize the benefits of the introductory laboratory class. Diagrams and pictures were included in the exercises to improve descriptions. Students were allowed multiple attempts with immediate feedback provided to help them learn from their mistakes. The study is a descriptive account of students' perceptions of the impact of online pre-laboratory exercises on their learning. Students recognized the value of the exercises in improving their organization, their preparedness for the laboratory class, and their understanding of the chemistry concepts of the weekly experiments. The increased flexibility of doing pre-laboratory exercises online and the increased feedback to students were two important aspects of this project that nearly all students recognized as being beneficial to their learning.

Professor Julie Millard, The Dr. Gerald and Myra Dorros Professor of Chemistry and son Zoli Nagy

Julie Millard, The Dr. Gerald and Myra Dorros Professor of Chemistry and her son, Zoli Nagy, reading A Series of Unfortunate Events: The Ersatz Elevator by Lemony Snicket

Photochemical Generation and Intramolecular Chemistry of β-Alkoxycarbenes

The photolytic phenanthrene-based precursors for both β-methoxycarbene and β-ethoxycarbene were synthesized with and without a deuterium label attached to the a carbon. The incorporation of this deuterium label allowed distinction between a 1, 2-H shift and a 1, 2-O shift pathway to the respective alkyl vinyl ether, without the influence of a primary kinetic isotope effect. Photolyses of these precursors gave rearrangement products of the expected β-alkoxycarbenes. In the case of β-methoxycarbene, no methyl vinyl ether was observed due to its volatility. However, the appearance of aldehyde peaks in the NMR spectra, from an apparent further rearrangement to acetaldehyde through an enol intermediate, indicated that a 1,2-H shift had occurred. Ethyl vinyl ether was isolated following the photolysis of the β-ethoxycarbene precursor. Quantification of the two pathways showed less than 2% undergoing an ethoxy shift to the ethyl vinyl ether. Yield experiments on this photolysis demonstrated a maximum yield of β-ethoxycarbene as 43%, though this decreased as the experiment continued. Computational work on the β-ethoxycarbene system indicates that the triplet scate is more stable than the singlet. In addition, the activation energy to the 1.2-H shift pathway is remarkably low and is clearly consistent with the observed overwhelming preference for this pathway in the experiment.

Pressure Perturbation Calorimetry and Guest-Host Chemistry of NDMG and N-MAP with p-Sulfonatocalix[6]arene

The aim of this project is to provide an explanation for recently obtained binding constants for two similar guest molecules, NDMG and N-MAP, with a p-sulfonatocalix[6]arene host in ammonium acetate buffer. This work was done primarily using pressure perturbation calorimetry, which is a technique that determines the coefficient of thermal expansion, α, which is in turn related to the solute molecule's effect on the order of the surrounding water molecules. A series of experiments were designed to test the effects of suspected confounding variables on the validity of PPC data. PPC was then used to study NDMG and N-MAP in ammonium acetate buffer. NDMG exhibited a minimum in α as function of temperature, while N-MAP did not. This difference was theorized to be due to the formation of an intramolecular hydrogen bond in monocationic NDMG that would lower the heat capacity of the molecule and better distribute the molecule's charge. Computational work and nuclear magnetic resonance spectroscopy confirmed that monocationic, ring-closed NDMG has less concentrated charge and more constrained motion than monocationic, ring-open NDMG. This evidence supports the theory that monocationic NDMG forms an intramolecular hydrogen bond and that this may be responsible for the minimum in α. This difference may explain the differences in binding constants between NDMG and N-MAP.

Oxygen and hydrogen isotopic ratios and chemistry in semiarid land river water, Southwest Victoria, Australia

Salt in a salt lake accumulated as a result of perfect evaporation of inflow water during the dry season. Water in a salt lake had a high salinity and its isotope indicated a little evaporation in the wet season because precipitation replenished the salt lake and there was no residual water during evaporation process in salt lake. In a marsh, both perfect and partial disappearance of water by repeated evaporation and water supply from upstream contributed to high salinity and high isotopic ratios because residual water had high isotopic ratios and dried areas accumulated salt. On the other hand, salinity and isotopic ratios depended on ratio of evaporation and water supply during evaporation excluding perfect disappearance of water.