Chemical Hazards: Concentrated Acids, Concentrated Bases and an Oxidising Agent
This is a safety experiment, which allows the students to observe the damage that concentrated acids and bases and potassium permanganate can to different materials in a controlled environment. The students write their own Material Safety Data (MSD) Table and in group discussions discuss their own MSD Tables with actual MSD Sheets.
Electronic Spectroscopy as a Probe for the Mechanism of a Chromium(II) Catalysed Substitution Reaction
The activities involved in this experiment are:
Prepare and/or collect of solution state spectra of a series of homoleptic complexes of chromium(III) so as to arrive at an experimentally-based spectrochemical series. Collection of the solid state UV-Vis spectra of CrCl3 (anhydrous) and KCr(SO4)2.12H2O so as to determine (using the rule of average environment) the coordination environment of chromium(III) in the salt CrCl3.6H2O. Establish the connection between the solution and solid state spectra and use this to confirm that over a short timescale the coordination sphere of chromium(III) in CrCl3.6H2O does not change on dissolution. Determine the relative rates of the first and second aquation reactions of [CrCl2(OH2)4]+
Record the UV-Vis spectra of the product(s) formed from the chromium(II) catalysed dissolution of anhydrous chromic chloride and use the rule of average environment to deduce (1) whether a single or several products are formed during the reaction and (2) identify the coordination environment of the chromium(III) product.
Finding the Solubility of Calcium Hydroxide by Three Different Methods
he concentration of dissolved calcium hydroxide in a saturated solution of calcium hydroxide is determined by three independent methods: gravimetric analysis (evaporation of the water followed by weighing the solid residue); titrimetric analysis (titration with hydrochloric acid); and, pH measurement (via estimation of the concentration of hydroxide ion present).
An Aldol Condensation
In this reaction a base-catalysed crossed aldol condensation will be performed, in which an enolate anion from a ketone adds to an aromatic aldehyde. It is followed by a virtually spontaneous dehydration. Aldol reactions with two carbonyl compounds usually give mixtures of products: both reactants might form enolate anions, and each anion could react with either carbonyl compound – hence, four possible products.
Chemistry of alpha-Amino Acids: A Multi-Step Synthesis of Hippuric Acid and Derivatives
In this experiment, you will synthesise hippuric acid starting from glycine, an amino acid that is commonly found in proteins, and benzoyl chloride. The reaction of glycine with benzoyl chloride in the presence of an alkaline catalyst yields the amide, benzoylglycine (hippuric acid). The name comes from the Greek work for horse, hippos, because hippuric acid was first isolated from the urine of horses. With hippuric acid in hand, you will prepare a heterocycle, 4-benzylidene-2-phenyloxazol-5-one – the overall scheme is illustrated below. This heterocyclic system is activated towards new carbon-carbon bond formation and can be utilised for the synthesis of new α-amino acids.
Separation and Estimation of Organic Compounds
Chromatographic techniques are used to examine the coloured components (which include carotene and chlorophyll) of a mixture obtained by extraction of green leaves with acetone, and to separate the carotene from the other components. Students use two types of chromatography, thin layer and column chromatography, the former illustrating to the students the feasibility of separating components and the latter being used to separate the carotene to allow its quantitative determination. Spectrophotometry Chlorophyll-a, the green pigment in the leaf extracts used to determine the percent by weight of each of chlorophyll and carotene in the leaves. The amount of chlorophyll in the leaf extract mixture can be quantified without its isolation from the leaf extract mixture.
A Problem Oriented Approach to Understanding Analytical Chemistry and the use of Portfolio Assessment
Students were asked to submit a portfolio which provided evidence of their learning and contained the following elements: a summary of the issue/problem to be addressed, a laboratory report, examples of self directed learning, examples of shared learning resources and a reflective log. In this paper emphasis will be placed on the laboratory component but there will be some discussion of the other student learning elements. The lecturer chose amino acid analysis as the problem/issue to be addressed by the students. It was chosen because it provided an example of a sample that is not ideal for chromatographic analysis.
An Oscillating Chemical Reaction
The purpose of this experiment is to set up and observe the well-known oscillating reaction involving the manganese-catalysed decomposition of hydrogen peroxide by iodate. The various reagents required are prepared at the required concentrations from the bulk chemicals. The oscillations produce a cyclic colour change in a starch indicator, allowing the reaction to be followed photometrically using simple equipment. A basic analysis of some kinetic features of the reaction is carried out, using the photometric data recorded during the experiment.
Determination of Copper(II) Ion Concentration through Absorption Colourimetry
Students are given a stock solution of 0.25 M copper(II) nitrate, Cu(NO3)2, and then they make a series of accurate dilutions. They then use the PASCO Colourimeter to produce a calibration absorption curve, and find the equation of best-fit. The absorbance from a sample of Cu(NO3)2 of ‘unknown’ concentration is measured and the calibration curve and its linear regression equation is then used to calculate the unknown’s concentration.
Thermodynamics of Ligand Binding
In this experiment, a synthetic and non-natural porphyrin ligand, meso-tetraphenylporphyrin will be used as a tetradentate ligand for zinc ions, and the thermodynamics of binding of an extra ligand to the zinc will be investigated. Students prepare 10 solutions containing the zinc porphyrin complex with varying amounts of an allocated p-substituted pyridine, as the ligand. The visible spectra are recorded of each solution and the binding constants determined. The equilibrium constants for the zinc tetraphenylporphyrin with the p-substituted pyridines follow the order which would be predicted on the basis of the electron-donating or electron-withdrawing nature of the para-substituent.
Calculating Simple Force Constants with Computational Quantum Chemistry
This experiment allows the student to calculate the force constant by quantum mechanical calculations for the three diatomic molecules, F2, O2 and N2. It uses the Gaussian and Mopac quantum chemistry codes running on a server and accessed by forms through a web browser. A selection of Hartree-Fock and Density Functional Theory methods are available, along with the semi-empirical AM1 and PM3 methods. Rather than using the “black box” calculation of the force constants from a calculation of the frequencies, here the student calculates the energy at the optimum bond length and with the bond length increased and decreased by 0.01 A. They then fit a parabola through these points to calculate the second derivative and hence the force constant. For some more advanced calculations the appropriate energies are provided rather then calculated.
Investigation of Rotation of Plane Polarised Light using a Home Made Polarimeter
Students construct a simple polarimeter and use it to investigate the optical activity of common sugar (sucrose). Sucrose is an optically active molecule and therefore rotates the plane of polarisation of plane polarised light. Students have an opportunity to create a series of sugar solutions of known concentrations using an analytical balance and volumetric flasks.
Preparation and Properties of Three Nickel(II) Complexes
In this experiment three nickel(II) complexes with different geometries are synthesised. The magnetic moments of the complexes are measured in order to establish the correct geometry of each. Molecular mechanics calculations are used to rationalise the observed differences in geometry of two of the complexes.
Acetylation of Ferrocene
This experiment describes the Friedel-Crafts acylation of ferrocene with acetic anhydride, using phosphoric acid as the catalyst, to form acetylferrocene. It provides a means of introducing the chemistry of electrophilic aromatic substitution and the metallocenes. This material is part of the Level II lecture material at the University of Adelaide and this experiment provides a means of exploring this chemistry. As the reaction does not go to completion, chromatography is required to separate the product from the starting material. This experiment introduces how to carry out thin-layer and column chromatography. The students are expected to develop an experimental design, based on column chromatography, that will allow them to isolate pure material.
Isolation of Shikimic Acid from Star Aniseed
This laboratory experiment was designed as a practical component in the Natural Products Chemistry course (3rd year undergraduate) at Christchurch Polytechnic Institute of Technology, Christchurch, New Zealand. This experiment uses Soxhlet extraction followed by purification using ion exchange (Amberlite 1RA-400 resin), decolourisation using activated charcoal and recrystallisation – all useful techniques in natural product isolation. Subsequent charcoal decolourisation and recrystallisation afford pure shikimic acid in 2-7% yield. This experiment would also be relevant to organic chemistry courses.