Physical methods / analytical techniques
Discuss students responses with respect to the answer key.
This activty was developed for the IONiC VIPEr summer 2018 workshop, and has not yet been implemented.
Inorganic chemists often use IR spectroscopy to evaluate bond order of ligands, and as a means of determining the electronic properties of metal fragments. Students can often be confused over what shifts in IR frequencies imply, and how to properly evaluate the information that IR spectroscopy provides in compound characterization. In this class activity, students are initially introduced to IR stretches using simple spring-mass systems. They are then asked to translate these visible models to molecular systems (NO in particular), and predict and calculate how these stretches change with mass (isotope effects, 14N vs 15N). Students are then asked to identify the IR stretch of a related molecule, N2O, and predict whether the stretch provided is the new N≡N triple bond or a highly shifted N-O single bond stretch. Students are lastly asked to generalize how stretching frequencies and bond orders are related based on their results.
Evaluate the effect of changes in mass on a harmonic oscillator by assembling and observing a simple spring-mass system (Q1 and 2)
Apply these mass-frequency observations to NO and predict IR isotopic shift (14N vs. 15N) (Q3 and 4)
Predict the identity of the diagnostic IR stretches in small inorganic molecules. (Q5, 6, and 7)
Springs, rings, stands, and masses (100 and 200 gram weights for example).
Assemble students into small groups discussions to answer the questions to the activity and collaborate.
This LO has not been implemented; however, we recommend a few options for evaluating student learning:
implement as in-class group work, collect and grade all questions
have students complete the literature discussion questions before lecture, then ask them to modify their answers in another pen color as the in-class discussion goes through each questions
hold a discussion lecture for the literature questions; then for the following lecture period begin class with a quiz that uses a slightly modified problem.
This LO has not been implemented yet.
In honor of Professor Richard Andersen’s 75th birthday, a small group of IONiC leaders submitted a paper to a special issue of Dalton Transactions about Andersen’s love of teaching with the chemical literature. To accompany the paper, this literature discussion learning object, based on one of Andersen’s recent publications in Dalton, was created. The paper examines an ytterbium-catalyzed isomerization reaction. It uses experimental and computational evidence to support a proton-transfer to a cyclopentadienyl ring mechanism versus an electron-transfer mechanism, which might have seemed more likely.
The paper is quite complex, but this learning object focuses on simpler ideas like electron counting and reaction coordinate diagrams. To aid beginning students, we have found it helpful to highlight the parts of the paper that relate to the reading questions. For copyright reasons, we cannot provide the highlighted paper here, but we have included instructions on which sections to highlight if you wish to do that.
After completing this literature discussion, students should be able to
Count the valence electrons in a lanthanide complex
Explain the difference between a stoichiometric and catalytic reaction
Predict common alkaline earth and lanthanide oxidation states based on ground state electron configurations
Describe how negative evidence can be used to support or contradict a hypothesis
Describe the energy changes involved in making and breaking bonds
On a reaction coordinate diagram, explain the difference between an intermediate and a transition state
Explain how calculated reaction coordinate energy diagrams can be used to make mechanistic arguments
This is a paper that is rich in detail and material. As such, an undergraduate might find it intimidating to pick up and read. We have provided a suggested reading guide that presents certain sections of the paper for the students to read. We suggest the instructor highlight the following sections before providing the paper to the students. While students are certainly encouraged to read the entire paper, this LO will focus on the highlighted sections.
First 5 lines ending at the word high (you may encourage students to look up exergonic if that is not a term commonly used in your department)
Line 14 starting with “In that sense,” through the end of the paragraph
From the start through the word “endoergic” in line 22
Line 31 from “oxidation of” to the word “described” in line 33
Line 40 from “These” to the word “dimethylacetylene” in line 45
From the start to the word “appears” in line 4
The words “to involve” in line 4
Starting in line 4 with “a Cp*” to “transfer” in line 5
Results and Discussion
Paragraph 3 from the start through “six hours” in line 10
From the start to “solution” in line 3
From “This exchange” in line 10 to “allene” in line 11
From “Hence” in line 19 through the end of the paragraph
Paragraph 6 from the start through “infrared spectra” in line 19
Paragraph 7 from “Hence” in line 4 through the end of the paragraph
Mechanistic aspects for the catalytic isomerisation reaction of buta-1,2-diene to but-2-yne using (Me5C5)2Yb p 2579.
Synthesis of (Me5C5)2Yb(η2-MeC≡CMe).
Synthesis of (Me5C5)2Ca(η2-MeC≡CMe).
Reaction of (Me5C5)2Yb with buta-1,2-diene