Organic Chemistry

9 Jun 2019

Inorganic Chemistry

Submitted by Caroline Saouma, University of Utah

9 Jun 2019

Chem 165 2018

Submitted by Adam R. Johnson, Harvey Mudd College

This is a collection of LOs that I used to teach a junior-senior seminar course on organometallics during Fall 2018 at Harvey Mudd College. There were a total of 9 students in the course. The Junior student (there was only one this year) was taking 2nd semester organic concurrently and had not takein inorganic (as is typical).

Subdiscipline:

Organometallic Chemistry

Topics Covered:

Bonding models: Discrete molecules

Catalysis

Chemical literature

Communication skills

Organometallic chemistry

Physical methods / analytical techniques

Professional skills development

Prerequisites:

First Semester Inorganic Chemistry / Foundation Course in Inorganic Chemistry

Organic Chemistry

Corequisites:

No Corequisites

Course Level:

Upper Division

9 Jun 2019

1FLO: PCET and Pourbaix

Submitted by Anne Bentley, Lewis & Clark College

Evaluation Methods:

I graded each student’s problems as I would any other homework assignment, and they averaged about 80% on that part of the assignment. The other half of the total points for the assignment came from in-class participation.

Evaluation Results:

We had a rich conversation about this article in class; it was probably one of the most interesting literature discussion conversations I’ve had. Although this was the only introduction to Pourbaix diagrams in the course, 12 of 15 students correctly interpreted a “standard” Pourbaix diagram on a course assessment.

Description:

This set of questions is based on a single figure from Rountree et al. Inorg. Chem. 2019, 58, 6647. In this article (“Decoding Proton-Coupled Electron Transfer with Potential-pKa Diagrams”), Jillian Dempsey’s group from the University of North Carolina examined the mechanism by which a nickel-containing catalyst brings about the reduction of H⁺ to form H₂in non-aqueous solvent. Figure 3 in the article presents an excellent introduction to the use of Pourbaix diagrams and cyclic voltammetry to determine the mechanism of a proton-coupled electron transfer reaction central to the production of hydrogen by a nickel-containing catalyst.

Prerequisites:

Corequisites:

Topics Covered:

Physical methods / analytical techniques

Course Level:

Upper Division

Learning Goals:

Students should be able to:

- identify atoms in a multidentate ligand that can coordinate to a metal as a Lewis base

- outline the difference between hydride addition to a metal and protonation of a ligand in terms of changes to the overall charge of the complex

- analyze a Pourbaix diagram to predict the redox potential and pKa of a species

Subdiscipline:

Electrochemistry

Related activities:

Analyzing a journal article for basic themes, roles of authors, and the scientific method

A discussion on "Electrochemical formation of a surface-adsorbed hydrogen-evolving species"

Electrocatalysis and Proton Reduction

An Introduction to Electrocatalysis: Hydrogen Evolution from Mono and Binuclear Cobalt Complexes

Nanomaterials for Carbon Dioxide Reduction

Implementation Notes:

I have discussed the challenge of integrating literature discussions into my inorganic course in a BITeS post and the VIPEr forums. Each spring I try something a little different. This year I used three articles from the literature to frame our review of course material at the end of the semester, with each literature discussion occupying a one-hour class meeting.

In each case, the students completed problems before coming to class. While these problems were based on the journal articles, they did not require the students to read / consult the journal articles in order to complete the assignment. The students brought an electronic or paper copy of the article to class. I usually put students in groups (approximately 3 per group) and gave each group new questions to work on, which did draw from the article. After some time working in groups, each group presented their material to the rest of the class.

In implementing this particular literature discussion, I didn’t have any further questions for them. I walked through some of the other figures from the article (especially Figure 1). We discussed the authors’ use of color in creating Figure 3. We also reviewed the significance of horizontal vs vertical vs diagonal lines. Because I had not covered Pourbaix diagrams in the course, the activity was a good introduction to the concept.

Because these problems don’t require consultation with the article, they are suitable to use on an exam.

Time Required:

varies

9 Jun 2019

Triphenylphosphine: Transformations of a Common Ligand

Submitted by Bradley Wile, Ohio Northern University

Evaluation Methods:

This lab report is graded using the attached rubric (see faculty files).

Evaluation Results:

Over the last four iterations of this lab, the average total score was ~42/50 (n = 21). Students are generally good at recognizing that a redox process is occurring, though some struggle with this realization. Most students generate a Lewis structure with a dative bond, though some do not use the MO diagram to infer a reasonable direction for the dative interaction. I typically work through this with the students, asking them questions like "which orbitals have electrons?" and "what orbitals are interacting in your Lewis depiction?" This has been a good introduction to these synthetic and instrumental methods, and gives the lab partners an opportunity to divide up their responsibilities.

Description:

This experiment tasks students with preparing triphenylphosphine sulfide, and the corresponding I₂ adduct, then characterizing these products using common instrumental methods. Students are asked to consider MOs and tie this to their Lewis bonding depiction for the final product. This discussion is supported by WebMO calculations and tied to the experimental data obtained by the student.

If you would like to use this lab, please complete the feedback form (faculty files) and let me know how you adapt it. I would like to publish this procedure (eventually), and I am open to collaborative projects to get this to the best final form.

Course Level:

Upper Division

Prerequisites:

Organic Chemistry

Topics Covered:

Main group chemistry

Learning Goals:

After completing this lab report, students should be able to:

Construct an MO diagram for I₂, and relate this to the bonding in the Ph₃PS-I₂ complex
Using MO theory as a basis, decide on the best Lewis representation for Ph₃PS-I₂
Discover the wealth of bonding modes within main group species
Identify changes in the observable spectra for P(III) and P(V) compounds
Search and reference the primary chemical literature using correct ACS reference formatting

Subdiscipline:

Main Group Chemistry

Corequisites:

No Corequisites

Equipment needs:

This experiment is run using our in house instumentation including:

NMR spectrometer capable of acquiring ¹H and ³¹P spectra
IR spectrometer
UV-vis spectrometer (we acquire data on a Spec200 that works just fine for this)
GC-MS (optional)

These spectra are provided as faculty files. If you do not have any of these capabilities, the spectra may be given to students as a handout.

Additionally, the experiment will require use of round-bottomed flasks, condensers, beakers, scintillation vials, hot plates, and gravity filtration apparatus (stemless if hot filtration required). Solvents and reagents are typically already present in the department, or may be purchased at reasonable cost.

Implementation Notes:

I use this lab as the first experiment of the semester, and begin the first week's activity after the introduction and lab safety discussion.

Prior to running the experiment, I prepare approximately one batch of each product (Ph₃PS and Ph₃PS-I₂) in case of a laboratory mishap. The products are indefinitely stable under ambient conditions.

I do not describe the reaction as a redox process, or suggest a bond order (i.e. I try to write the formula for Ph₃PS with an ambiguous bond order, as shown here).

Depending on the age of your bottle of Ph₃P, you may spot a small quantity of Ph₃P=O in the ³¹P spectrum (small peak around 30 ppm in the included spectrum). This may be an opportunity to discuss connections to biochemistry or atmospheric oxidation, or ask students to draw Lewis depictions of these species.

I teach my students how to manually run their own NMR spectra using TopSpin at this point (they have previously learned ¹H and ¹³C using the autosampler). I typically discuss the differences between ³¹P{¹H} and ³¹P (non decoupled) spectra at this time. Note that the lab handout has some instructions specific to the Bruker software that may be updated if you use a different spectrometer.

Literature articles describing the crystal structure of the final adduct (and related I₂ species) are linked here. I have not typically gone into great detail about this, as the assembled I₂ ribbons can confuse the students that are just putting the basic concepts together.

Time Required:

Two full 3 hour labs, and approximately 1 additional hour (first week). If characterization is done outside of normal lab hours, this could be accomplished in one full 3 hour lab and one additional hour.

Web Resources:

Crystal structure of the triphenylphosphine sulfide-iodine addition complex J. Phys. Chem. 1968,72(5), 1561-1565

A new assembly of diiodine molecules at the triphenylphosphine sulfide template J. Chem. Soc., Dalton Trans., 1999, 3069-3073

Crystal structure of triphenylphosphine sulfide diiodine J. Chem. Soc., Dalton Trans., 1998, 1289-1292