Undergraduate Chemistry Laboratory Research Articles

Microwave Instruments: Green Machines for Green Chemistry?

In this column, the authors discuss the ease of using microwave ovens for various activities in the undergraduate chemistry laboratory and suggest a few models of microwave systems for readers to consider.

Thermodynamic Exploration of Eosin−Lysozyme Binding

We developed a modular pair of experiments for use in the undergraduate physical chemistry and biochemistry laboratories. Both experiments examine the thermodynamics of the binding of a small molecule, eosin Y, to the protein lysozyme. The assay for binding is the quenching of lysozyme fluorescence by eosin through resonant energy transfer. In both experiments, students measure fluorescence quenching at constant lysozyme concentration as a function of added eosin and determine the dissociation constant, KD, and ΔG° for binding. In the physical chemistry experiment, students repeat the fluorescence measurements at several temperatures to determine the temperature dependence of ΔG°, and therefore ΔH° and ΔS° as well. Typical student results yield a KD of (28.3 ± 7.5) μmol L−1 and a binding ΔG° of (−26.04 ± 0.70) kJ mol−1 at 25 °C. ΔH° and ΔS° of binding are found to be (−4.1 ± 2.5) kJ mol−1 and (73.9 ± 8.7) J mol−1 K−1, respectively. This pair of laboratories represents an interdisciplinary module in which students in different courses examine the same system but from different perspectives and with different emphases.

A New Java Program for Graphical Illustration of the Franck−Condon Principle: Application to the I2 Spectroscopy Experiment in the Undergraduate Physical Chemistry Laboratory

Requires FCIntensity.jar Themeasurement and subsequent analysis of I2 absorption and emission spectra is a standard experiment in the undergraduate physical chemistry laboratory (1-5). The observation of interesting intensity alternations in the dispersed fluorescence spectrum and the lack of clear alternations in the absorption spectrum are a manifestation of the Franck-Condon principle, which is an important concept in physical chemistry. Discussion of the Franck-Condon principle, although often neglected in the undergraduate curriculum, can illustrate the connection between vibrational eigenfunctions and transition probabilities. We have developed a portable, flexible, and user-friendly program to illustrate the relationship between Franck-Condon factors and the observed spectral intensities. Students also explore the effects of changing spectroscopic parameters on the predicted spectra. FCIntensity is a Java program that computes the eigenfunctions and eigenvalues of the Morse oscillator Hamiltonian using numerical methods. The program is easily uploaded and implemented on a personal computer and permits facile manipulation of input parameters (Figure 1). As part of the analysis of our I2 laboratory, the students are given the ground state Re (2.6664 A) value and asked to obtain the best-fit B-state Re by comparing the calculated intensity distribution to experiment. Although the calculated intensity patterns do not exactly match experiment (given the Morse approximation that can be discussed), only B-state Re values near 3 A provide an acceptable fit. The remarkable sensitivity is surprising to most students. The comparison between calculation and experiment also reveals the dependence of the spectrum to other parameters. For example, changes in Te, ve, and De for the B-state result in shifts of the spectral positions of all emission lines, while changes in De and ve for the ground state result in changes in the spacing between emission lines. Once the emission spectrum has been analyzed, we ask the students to use the program to simulate the measured absorption spectrum using the same parameters. Calculations using v00 =0, 1, 2 provide visual confirmation of the location of the hotbands and, through inspection of the vibrational wave functions, the origins of the nonoscillatory behavior relative to the emission spectrum.

O uso de aparelhos de micro-ondas domésticos em aulas experimentais de química orgânica: nitração de salicilaldeído

The use of microwave in chemistry has known benefits over conventional heating methods, e.g. reduced reaction times, chemical yield improvement and the possibility if reducing or eliminating the use of organic solvents. We describe herein a procedure for the nitration of salicylaldehyde in water using a domestic microwave oven, which can be used as an experiment in the undergraduate chemistry laboratory. The experiment involves safe and rapid preparation and identification of the position isomers by thin layer chromatography and 1H NMR, or by their melting points.

Quantification of Sugar Mixtures with Near-Infrared Raman Spectroscopy and Multivariate Data Analysis. A Quantitative Analysis Laboratory Experiment

An experiment for Raman spectroscopy in combination with multivariate data analysis was designed and implemented in the undergraduate analytical chemistry laboratory curriculum. Raman spectroscopy is currently considered among the most important nondestructive routine optical analysis tools. An experiment is presented demonstrating the capability of Raman spectroscopy in combination with principal components analysis and regression (PCA/PCR), which was applied to determine the composition of complex sugar mixtures that cannot be adequately quantified using conventional univariate analysis methods.

Analysis of Dextromethorphan in Cough Drops and Syrups: A Medicinal Chemistry Laboratory

Fluorescence spectroscopy is used to determine the quantity of dextromethorphan hydrobromide (DM) in over-the-counter (OTC) cough drops and syrups. This experiment is appropriate for an undergraduate medicinal chemistry laboratory course when studying OTC medicines and active ingredients. Students prepare the cough drops and syrups for analysis, compare their results with analysis of a DM standard solution and explore interference from other ingredients (food coloring, corn syrup, and methyl cellulose). Students also perform a standard addition analysis to obtain a quantitative result for the quantity of DM in a cough medicine. This experiment can be a straightforward laboratory exercise to be completed in one laboratory period or an open-ended investigation spanning two or more laboratory periods. This exercise gives students experience in chemical analysis of an OTC medicine and could be extended to other medications or food products.

Comparison of Biochemical and Chemical Digestion and Detection Methods for Carbohydrates

There is a multitude of chemical and biochemical detection methods for sugars. Which ones would be most practical in an undergraduate laboratory setting? How to best detect non-reducing disaccharides? How to make such lab fun for students to perform? After trying several spectrophotometric methods, it was found that chemical detection by dinitrosalicylic acid and biochemical detection by hexokinase/glucose-6-phosphate dehydrogenase reagent are most appropriate. Sucrose, a non-reducing disaccharide was digested chemically with hydrochloric acid and biochemically with invertase. It was concluded that chemical detection and biochemical detection compliment each other. Chemical digestion method was preferred over the digestion by invertase. These methods were applied for testing the validity of sugar ingredients printed on drink labels as well as the measurement of sugar levels in ripening bananas at two different conditions. The comprehensive comparison of these methods and the detection of sugar concentrations in interesting samples might serve as a basis for an undergraduate chemistry laboratory.

Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment

This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic acid at neutral pH. Cyclic voltammograms of L-ascorbic acid are different on these electrodes, owing to the different surface charge of the SAMs. Cysteamine-modified electrodes give a sharper oxidation peak at a smaller overpotential and thus are more suitable for measuring the concentration of L-ascorbic acid in an aqueous solution. A linear calibration curve is obtained using such an electrode, permitting the determination of L-ascorbic acid content in a vitamin C tablet. This experiment provides a means for teaching the basics of voltammetry, teaching the effect of chemical modification of the electrode surface on the electrode reaction, and providing students with hands-on experience in fabricating and utilizing electrochemical sensors. Additionally, it can be completed within three hours and is suitable as an undergraduate laboratory experiment.

Magnetic Field Gradient Calibration as an Experiment To Illustrate Magnetic Resonance Imaging

A nuclear magnetic resonance (NMR) spectroscopy experiment for the undergraduate physical chemistry laboratory is described that encompasses both qualitative and quantitative pedagogical goals. Qualitatively, the experiment illustrates how images are obtained in magnetic resonance imaging (MRI). Quantitatively, students experience the relationships between gradient strength, spectral width, and the quality of the obtained projection images as they calibrate the maximum field gradient strength of the instrument. They also find out the size of a trapped air bubble in their sample in close analogy how one could obtain information on physical sizes of objects in MRI.

ATR–FTIR Spectroscopy in the Undergraduate Chemistry Laboratory. Part I: Fundamentals and Examples

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for measuring the infrared spectra of solids and liquids as well as probing adsorption on particle surfaces. Several examples of the use of FTIR-ATR spectroscopy in different undergraduate chemistry laboratory courses are presented here. These examples include measuring the infrared spectra of solid and liquid organic compounds commonly used as unknowns and of inorganic solids synthesized by students. The use of ATR-FTIR spectroscopy in the upper-level physical chemistry laboratories will be discussed in Part II where a new experiment involving the adsorption of ions from solution onto oxide particle surfaces is introduced. In addition to the implementation of ATR-FTIR spectroscopy into the undergraduate curriculum, students involved in undergraduate research can use this technique to get high-quality publishable data on a number of interdisciplinary chemically-relevant interesting research projects.

ATR–FTIR Spectroscopy in the Undergraduate Chemistry Laboratory. Part II: A Physical Chemistry Laboratory Experiment on Surface Adsorption

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for measuring the infrared spectra of solids and liquids as well as probing adsorption on particle surfaces. The use of FTIR-ATR spectroscopy in organic and inorganic chemistry laboratory courses as well as in undergraduate research was presented in Part I as well as background information and the fundamentals of the ATR-FTIR technique. In Part II, the use of ATR-FTIR spectroscopy in the upper-level physical chemistry laboratories is discussed. A new experiment involving the adsorption of ions from solution onto oxide particle surfaces is introduced. In this laboratory experiment, students use ATR-FTIR spectroscopy to determine the Langmuir adsorption constant, Kads, for sulfate ion adsorbed on 2 particles at pH = 3. A thin film of oxide particles deposited onto the ZnSe ATR element is exposed to solutions of different sulfate concentrations. The infrared spectrum of adsorbed sulfate can be measured in this way. This experiment, which can be easily implemented into an upper-level chemistry curriculum, introduces students to several concepts including surface adsorption, oxide surface chemistry, and environmental interfacial processes.

Extensions of a Basic Laboratory Experiment: [4+2] and [2+2] Cycloadditions

We describe an extended third-year undergraduate chemistry laboratory exercise in which a number of techniques and concepts are applied to the same set of chemical reactions. The reactions are the photochemical and thermal cycloadditions of s-nitrostyrene and 2,3-dimethylbutadiene. This can be viewed as a single long lab or a series of connected exercises exploring a number of themes. This serves as an example of the goals and pedagogy used in a course designed to prepare students for a fourth-year undergraduate thesis. The exercises include synthesis, NMR spectroscopy, and computer-based molecular modeling. The same reagents are used, but the photochemical reaction gives the [2+2] product and the thermal reaction produces the [4+2] product. These reactions are used as a basis for discussions of a number of topics: the Woodward�Hoffmann rules, stereochemistry and regiochemistry, kinetic versus thermodynamic control of reactions, analysis of stereochemistry by 1D NMR, introduction of 2D NMR methods, molecular modeling, and use of computer programs for accurate visualization. This set of exercises is an example of an extension of the typical three-hour lab into more detailed investigations and an introduction to research methods

Synthesis and Characterization of Aldol Condensation Products from Unknown Aldehydes and Ketones

An experiment for the undergraduate chemistry laboratory in which students perform the aldol condensation on an unknown aldehyde and an unknown ketone is described. The experiment involves the use of techniques such as TLC, column chromatography, and recrystallization, and compounds are characterized by 1H NMR, GC–MS, and FTIR. This experiment provides the students with a thorough exercise in the practical aspects of organic chemistry. It requires students to think like researchers and allows them the opportunity to independently apply previously learned techniques in the laboratory.

Teaching the Rovibronic Spectroscopy of Molecular Iodine

Molecular iodine absorbance and fluorescence spectroscopy has a long history in the undergraduate physical chemistry laboratory curriculum. A review of articles from the pedagogical literature reveals surprising variability in reported X-state and B-state potential parameters derived from such well-studied spectra. The variation is a result of errors in spectral interpretation and analysis, and this article clarifies the correct methods for treating the data. Parameters obtained from student data are compared with accepted values from the primary literature, and expectations for accuracy and precision are established. This article also points out that the internuclear separation of X-state I2 can be calculated from the spacing of an easily resolved rotational doublet in the argon ion laser-induced fluorescence spectrum. This doublet has not been identified before in pedagogical articles.

From the Research Bench to the Teaching Laboratory: Gold Nanoparticle Layering

The emphasis currently being placed on research and development of nanotechnology strongly supports the introduction of nanoscience techniques and methodology into the undergraduate chemistry laboratory curriculum. The procedures presented within are designed for undergraduate chemistry students to experiment with synthetic, mechanistic, and measurable properties of gold nanoparticles and layering techniques. Methodology involves the synthesis of gold colloidal suspensions, attachment of a functional group to glass with subsequent creation of self-assembled monolayers (SAMS) through deposition of gold nanoparticles, and measurements of wavelengths, absorbance, and conductivity. Educational emphasis includes an understanding of the nanoscale and an exposure to nanotechnology through the synthesis and layering of gold nanoparticles.

High-Resolution Vibration–Rotation Spectroscopy of CO2: Understanding the Boltzmann Distribution

In this undergraduate physical chemistry laboratory experiment, students acquire a high-resolution infrared absorption spectrum of carbon dioxide and use their data to show that the rotational�vibrational state populations follow a Boltzmann distribution. Data are acquired with a mid-infrared laser source and infrared detector. Appropriate absorption peak assignments are made by comparison of the experimental spectrum with the high-resolution transmission molecular absorption (HITRAN) database. Integrated absorption peak areas are used as a measure of relative rotational�vibrational state populations. The effect of temperature on the population distribution is explored by sampling the absorption spectrum at several different temperatures, giving students the opportunity to observe the properties of a Boltzmann distribution.

A rubric to characterize inquiry in the undergraduate chemistry laboratory

Download options Please wait... Article information DOI https://doi.org/10.1039/B6RP90031C Article type Paper Submitted 31 Dec 2006 Accepted 14 Mar 2007 Download Citation Chem. Educ. Res. Pract., 2007,8, 212-219 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions A rubric to characterize inquiry in the undergraduate chemistry laboratory M. E. Fay, N. P. Grove, M. H. Towns and S. L. Bretz, Chem. Educ. Res. Pract., 2007, 8, 212 DOI: 10.1039/B6RP90031C To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Michael E. Fay Nathaniel P. Grove Marcy Hamby Towns Stacey Lowery Bretz

Providing solutions through problem-based learning for the undergraduate 1st year chemistry laboratory

A PBL laboratory-based module for first year undergraduate chemistry has been developed and successfully implemented. Its aim was to develop the students’ practical and transferable skills, as well as their content knowledge and scientific understanding, and also to address the concern expressed in the literature over the effectiveness of the traditional laboratory courses to achieve these aims. The PBL module also encouraged students to prepare for their laboratory session in an active and collaborative manner through pre-lab exercises. By combining elements of group work, discussion, hands-on activities and alternative assessment methods, the students were provided with an environment conducive to meaningful, deep learning. We describe how the PBL module was developed by adapting the experience for the students rather than changing the experiments. Specific examples from analytical, physical and organic chemistry are given with a focus on the pre-laboratory exercises, associated group work, and the assessment methods, as well as on the actual practical work. [Chem. Educ. Res. Pract., 2007, 8 (3), 347-361.]

A Polymer in Everyday Life: The Isolation of Poly(vinyl alcohol) from Aqueous PVA Glues. An Undergraduate Chemistry Experiment

In this article, we present a simple undergraduate chemistry laboratory involving the polymers commonly used in everyday life and the IR spectroscopy for functional groups identification. The polymer contained in the PVA glue is further hydrolyzed to poly(vinyl alcohol) in dilute aqueous solution via the base hydrolysis of the acetate groups. The IR spectra of three related polymers, the poly(vinyl acetate) in white glue, the PVA in the aqueous PVA glue, and the resulting PVA, are recorded. The differences in these spectra are rationalized with the molecular structures of the polymers.

Using a Spreadsheet to Fit Experimental pH Titration Data to a Theoretical Expression: Estimation of Analyte Concentration and Ka

A method of determining analyte concentration and Ka by least-squares fitting experimental acid–base pH titration data to a single theoretical expression is presented. The fitting is carried out using the Solver Add-in of the ubiquitous Excel spreadsheet program. The theoretical expressions used in this article are easily derived using the systematic treatment of equilibrium and alpha fractions, and therefore this method of analysis is appropriate for the typical undergraduate analytical chemistry laboratory–lecture sequence.