“You’re blind, so I advise you to choose history as your major.” The American Chemical Society and our home institutions have established Diversity, Equity, Inclusion, and Respect (DEIR) as core ...values. “You’re blind. Just sit in the corner and take notes as the other students dictate their observations to you.” But how do we operationalize this call both to implement our DEIR values and at the same time challenge our own assumptions about the differently abled? “I can’t imagine being a chemistry major if you can’t see the color changes!” This commentary describes my journey to better embed DEIR values into my work as a chemist and educator, and hopefully it will be useful to you as you wrestle with similar topics. “You want to be a chemistry major? Have I got an undergraduate research project for you!” The journey begins with a simple yes answer and proceeds through a challenge to underscore an enthusiasm for DEIR practices with a more distinct theoretical foundation that undergirds our DEIR-focused work. This requires expanding our toolkit in the basics of quality teaching with an emphasis on positive student learning outcomes and experiences, all geared toward greater representation and broader participation in the chemical enterprise. Importantly, this also requires a change in perspectivea new paradigm in which DEIR objectives inform the very structure of our educational system. In summary, this commentary recounts the resources that allowed me to change my educational paradigm, many of which came from outside the world of chemistry.
Plants actively perceive and respond to perturbations in their cell walls which arise during growth, biotic and abiotic stresses. However, few components involved in plant cell wall integrity sensing ...have been described to date. Using a reverse-genetic approach, we identified the Arabidopsis thaliana leucine-rich repeat receptor kinase MIK2 as an important regulator of cell wall damage responses triggered upon cellulose biosynthesis inhibition. Indeed, loss-of-function mik2 alleles are strongly affected in immune marker gene expression, jasmonic acid production and lignin deposition. MIK2 has both overlapping and distinct functions with THE1, a malectin-like receptor kinase previously proposed as cell wall integrity sensor. In addition, mik2 mutant plants exhibit enhanced leftward root skewing when grown on vertical plates. Notably, natural variation in MIK2 (also named LRR-KISS) has been correlated recently to mild salt stress tolerance, which we could confirm using our insertional alleles. Strikingly, both the increased root skewing and salt stress sensitivity phenotypes observed in the mik2 mutant are dependent on THE1. Finally, we found that MIK2 is required for resistance to the fungal root pathogen Fusarium oxysporum. Together, our data identify MIK2 as a novel component in cell wall integrity sensing and suggest that MIK2 is a nexus linking cell wall integrity sensing to growth and environmental cues.
Nuclear magnetic resonance (NMR) spectroscopy is an indispensable tool for structure analysis. Students traditionally learn to interpret NMR spectra by using correlation tables to connect ...substructural units to their respective signals. This activity presents a successfully implemented classroom exercise in which students discover for themselves the pattern underlying the chemical shift correlation. To accomplish this goal, students analyze sets of NMR data selected to highlight paradigms of molecular structure on chemical shift, including the effects of electronegative elements, double bonds, and aromatic systems as well as cumulative effects. This approach improved students’ abilities to interpret spectra and use correlation tables.
The stabilizing features of a macrocyclic sesquiterpene-derived cation were explored using quantum mechanical calculations. The monocyclic humulyl cation, the product of 11,1-cyclization of farnesyl ...diphosphate, is the product of the first committed step in the enzymatic synthesis of a range of structurally diverse sesquiterpenes, including humulene (monocyclic); caryophyllene (bicyclic); and protoilludene, pentalenene, and isocomene (tricyclic). These natural products are formed via carbocation cascades that are directed in part by the conformation of the humulyl cation. Understanding the mechanistic details of product formation requires an understanding of the conformational preferences of this fundamental intermediate. Replacing the carbocation with borane (preserving π-accepting capabilities), ammonium (preserving positive charge), and methylene (preserving neither π-accepting capabilities nor charge) provides a systematic method to distinguish electrostatic and orbital effects on structure and internal stabilization. Several modes of internal stabilizationhyperconjugation, transannular π(alkene)···C+ and transannular C–H···C+ interactionswere uncovered, confirming and extending previous studies on this and similar systems.
superscript 1H NMR spectroscopy is a molecular characterization technique that is ubiquitously used in research and teaching laboratories alike. Strategic deuteration of molecules is a commonly ...employed technique in the deconvolution of superscript 1H NMR signals. Here this approach is applied in a second-year chemistry course in which students synthesize 4-methoxychalcone using the Claisen-Schmidt variant of the foundational aldol reaction. The superscript 1H NMR spectrum is complicated by a crowded aromatic and alkene region due in part to extensive conjugation through the two phenyl groups surrounding an alpha,beta-unsaturated ketone. This report demonstrates that students gain competence and confidence in making superscript 1H NMR assignments when presented with a curated set of selectively deuterated chalcones rather than the corresponding spectrum of the fully protiated chalcone. While deuteration does not resolve all of the challenges associated with interpreting this spectrum, it is an invaluable tool to complement chemical shifts (including the predictive nature of resonance structures), integration, and spin-spin splitting. A proposed lecture is presented that is timed to correlate with the performance of the chalcone synthesis lab. Assessment data collected before and after the lecture and then again on the final exam point to the effectiveness of this approach.
Friedel–Crafts alkylation reactions using a curated set of alcohols provide students with the opportunity to combine the study of electrophilic aromatic substitution with carbocation rearrangements. ...In this experiment students may be presented with up to nine alcohols that yield six products, all synthesized under identical reaction conditions. They distinguish their products using a range of instrumental methods including infrared, 1H NMR, and 13C NMR spectroscopies, and mass spectrometry. Additional characterization is provided by the determination of melting point/mixed-melting point and gas chromatographic retention time. Students work in teams to assign structures to their individual reaction products; providing nine starting materials ensures minimal duplicates in a given laboratory section. As students interpret their data, some discover that a carbocation rearrangement occurred, resulting in isolation of only one product despite starting from a pair of isomeric reagents. This laboratory provides students with the opportunity to engage in a range of laboratory and problem-solving skills, and thus is designed to be performed toward the end of a two-semester organic chemistry sequence.
Students analyzed a set of 34 carboxylic esters using 1H nuclear magnetic resonance (NMR) spectroscopy to examine paradigmatic examples of spin–spin coupling, a foundational concept used to determine ...molecular structure by NMR spectroscopy. The ester functional group provides excellent chemical shift dispersion so that students were able to analyze well-resolved peaks and to apply concepts of chemical shift, line shape, and integration to the analysis of molecular substructures. A laboratory activity combining molecular models, worksheets, and NMR data collection and analysis provided students with the ability to predict and to analyze spectra representing spin–spin splitting for N = 0–6 (where N is the number of three-bond neighbors that are hydrogens).
Nuclear magnetic resonance (NMR) spectroscopy is an integral part of the undergraduate chemistry curriculum. In addition to structure determination, NMR spectroscopy is used to analyze chemical ...reactions and equilibria in situ. Determination of the position of equilibria is well-suited to NMR analysis in the undergraduate laboratory as an extension of peak identification and signal integration, and the determination of keto–enol equilibrium remains a popular undergraduate laboratory experiment. Several factors affect the position of keto–enol equilibrium, defined here as K e/k = enol/keto, including structure (steric bulk, conjugation, electron-withdrawing/donating groups, resonance), temperature, and solvent. A judiciously selected set of compounds that have a common 1,3-dicarbonyl moiety with progressively changing ligands at the 1 and 3 positions is presented. This array allows students to investigate structure–function relationships that affect keto–enol equilibrium in a cumulative fashion and affords instructors a broad selection of compounds for study in both introductory and advanced laboratory courses using a variety of pedagogic approaches.
We describe accommodations that we have made to our applied computational–theoretical chemistry laboratory to provide access for blind and visually impaired students interested in independent ...investigation of structure–function relationships. Our approach utilizes tactile drawings, molecular model kits, existing software, Bash and Perl scripts written in-house, and three-dimensional printing in a process that allows a blind or visually impaired student to satisfy her or his curiosity about structure–function relationships with minimal assistance from sighted co-workers.
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Quantum chemical calculations coupled to experiments were used to predict covalent hydration propensities of biologically relevant α-ketoamides. Experimentally determined hydration ...equilibrium constants for related ketones and aldehydes were compared to computationally determined values to develop a method for predicting hydration equilibrium constants. This method was used on six newly synthesized α-ketoamides to experimentally verify computational predictions. A correlation between calculation and experiment was observed and applied to models of several pertinent APIs. Our results indicate that the keto form is favored for practically all α-ketoamides in biological environs.
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