Reaction mechanisms

30 Jun 2016
Evaluation Methods: 

This LO was created at the VIPEr Workshop in June 2016 and has not yet been evaluated.

Some possible evaluation methods:

  • The LO could be evaluated from written student work individually or from small groups, from the in-class discussion, or both. One method may be to allow students to write their answers to the discussion questions as homework in one color pen and then have them make changes during the in-class discussion in a different color pen. The resulting worksheets could be collected and some questions graded based on individual student answers and some questions graded based on group answers.

  • Faculty could ask students to read the article and then divide them into groups to prepare short presentations on different concepts (NMR, CV, electron-counting, etc.). These presentations could be rated by faculty and students.

  • Faculty could ask problem set, quiz and/or exam questions related to questions and concepts. A problem set related to this LO is posted on VIPEr.

Evaluation Results: 

This LO was created at the VIPEr Workshop in June 2016. No evaluation results have yet been obtained but two of the team members who created this LO will be using it in their classes during AY2016-2017. We will report back on the evaluation results.

Description: 

This literature discussion is designed for upper-level inorganic chemistry students. The article explores the motivations, design, and characterization of novel nickel(II) and nickel(IV) complexes for carbon-heteroatom bond forming reactions. Students can apply and integrate their knowledge of organic chemistry mechanisms, organometallic chemistry, and techniques for characterizing metal-ligand compounds that include NMR and CV.

This literature discussion was created as part of the NSF TUES VIPEr Workshop 2016 at the University of Michigan Ann Arbor based on the article “Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel (IV) complexes.”

Reference: Nicole M. Camasso and Melanie S. Sanford Science 2015, 347, 1218-1220.  DOI: 10.1126/science.aaa4526. Supplementary materials at www.sciencemag.org/ content/347/6227/1218/suppl/DC1.

The article was read by a team of seven workshop participants and the corresponding author, Prof. Sanford, presented the work to this audience. Following discussions with Prof. Sanford and between workshop participants, the LO was created.

Corequisites: 
Course Level: 
Subdiscipline: 
Learning Goals: 

 

General learning goals for literature discussions

 

Through reading this article, students will be able to…

  • integrate information from different subdisciplines of chemistry as they apply to answering research questions

  • extract information from figures, schemes, and tables in a scientific paper.

  • relate content in the current literature to concepts covered in class.

  • discuss scientific material with peers in an academic manner.

  • develop opinions and arguments related to a scientific paper and support them using external sources.

  • articulate the motivation and implications of scientific research presented in a scientific paper.

  • use references in the article to find and read literature precedents for concepts described in the primary article.

 

Learning goals specific to this literature discussion.

 

Students will be able to…

  • utilize general chemical knowledge to interpret research motivation and suggest potential issues (Question 1)

  • determine molecular geometries and count electrons for inorganic complexes (Question 3)

  • interpret and characterize intermediate products by NMR (Question 4)

  • demonstrate ability to interpret a voltammogram at a basic level. (Question 5a)

  • determine d-orbital splitting for multiple oxidation states and use this to determine potential characterization methods (Question 5b-d)

  • analyze NMR spectral data to compare characteristics (electron density, Lewis acidity, geometry, etc.) of metals discussed in the article. (Questions 6-8)

  • analyze the ligand environment around a metal center and make detailed comparisons between a series of related complexes. (Question 9)

  • draw transition states for and cite evidence to support a proposed reaction mechanism. (Question 10)

  • discuss the details of the nucleophilicity parameter and how it relates to reacton rate. (Question 11)

  • analyze the features of a cyclic voltammogram and compare with chemical reactivity (Question 12)

Implementation Notes: 

We have included a wide range of discussion questions, but expect that those who adopt this LO will pick and choose questions as they see fit.

There are a couple ways we plan to implement this literature discussion:

1. Students will read the article and answer a few of the simpler questions before coming to class. In class, students will discuss several questions at a time in small groups, followed by whole class discussion. Small groups may revise their answers accordingly, and will submit their group answers in addition to their individual responses at the end of the period.

2. Students will be divided into small groups and assigned a question from the lit exercise, then given 1 week to read over the article outside of class. During this time, students will be expected to answer questions 1-3 individually, and work with their groups to answer their assigned question. Each group will share their thoughts and opinions regarding the answers to their assigned question by presenting to the entire class in a “chalk talk” type discussion at the white board. Groups will be provided with images of any figure listed in the paper and lit discussion exercise in powerpoint so they can project images relevant to their discussion to the entire class.

Time Required: 
1-2 class periods for entire LO. Can be modified to be shorter
30 Jun 2016
Evaluation Methods: 

Informally faculty will walk around the room evaluate and assist with the challenges students face as they go through the activity.

Every group of students will submit one set of answers that will be graded for accuracy. Some questions are lower-level and intended to help students identify key ideas and relevant data from the paper. These questions could be worth fewer points while more complex quesitons could be worth more points.

We envision that faculty members will not have a challenging grading load since the discussion will happen during class and most answers will generated during class discussion.

Evaluation Results: 

We have not yet tested this activity in the class.

Description: 

This literature activity is designed to introduce students to the concept of outer-sphere hydroboration catalytic reactions. It can be used after hydrogenation and hydroboration reactions have been introduced in class (typically covered in organic chemistry). Additionally, this activity allows students to apply their understanding of redox chemistry, acid base chemistry, and physical techniques to characterize products and elucidate reactions mechanisms.

The LO is built around a paper by the Szymczak group (JACS, 2015, 137, 12808-12814) where they describe the role of ligand design and its ability to be modified via acid-base reactions to change the reactivity of a hydroboration catalyst.

The LO has a modular design and can be taught in its entirety or in pieces. It also contains links to related LOs that can serve to reinforce, or introduce, concepts covered in this activity.

Corequisites: 
Prerequisites: 
Learning Goals: 

After completing this assignment students will be able to…

Lower-order thinking

  • Recognize the key features of a hydroboration outer-sphere catalytic mechanism
  • Define turnover frequency and explain how turnover frequency represents catalyst effectiveness
  • Label the nucleophile and electrophile in different hydroboration species
  • Explain the key features of a hydroboration outer-sphere catalytic mechanism
  • Describe how redox-potential affects the nucleophilicity of metal-hydride complexes
  • Describe how spectroscopy is used to help elucidate reaction mechanisms
  • Summarize key points from an article in the primary literature

Higher-order thinking

  • Elucidate how (de)protonation of the catalysts modulates their nucleophilicity
  • Write and revise a hypothesis
  • Compare and contrast hydroboration of nitriles using NaBH4 (stoichiometric) and an outer-sphere hydroboration catalyst
  • Generalize how (de)protonation of metal complexes modulates their nucleophilicity
  • Infer how the secondary coordination of metal complexes can alter reactivity
  • Optional: Apply symmetry rules to assign the point group of compounds
  • Optional: Connect spectroscopic experimental evidence to the symmetry of compounds
Subdiscipline: 
Implementation Notes: 

Note to the instrucutor: This activity has not been tried in class before. We look forward to hearing input from anyone who implements this LO.

Before reading the article students will generate their initial hypothesis as an exercise to test their initial understanding purely on theoretical background from the course (2016 Szymczak LitDiscussion-Handout). Students will then read the paper and during the next class period they will work in groups of 2 or 3 students to answer the questions about the paper (2016 Szymczak LitDiscussion).

This activity is intended to be modular; each section is divided according to themes. If an instructor wants to do the whole activity it is possible but each module can be taught independently. The hypothesis generation and revision prompts are also something that instructors might choose to leave out depending on the needs of the class.

The faculty member will alternate between periods of monitoring the students’ progress and having the class report out their findings.

Time Required: 
One class period
27 Jun 2016

A Guided-Inquiry Approach to Building a Catalytic Cycle

Submitted by Murielle Watzky, University of Northern Colorado
Description: 

This activity introduces students to fundamental types of organometallic reactions, and directs them to examine how each of these reactions affects the total electron count for the organometallic complex and the oxidation state of the central metal.  Students are then directed to use these reactions to build a sequence of steps for a catalytic cycle.

Learning Goals: 

Upon completion of this activity, students will be able to…

-       discuss fundamental organometallic reactions.

-       determine how fundamental organometallic reactions affect the total electron count in an organometallic complex and the oxidation state of the central metal.

-       apply their knowledge of fundamental organometallic reactions to put together a catalytic cycle.

-       understand the cyclic nature of catalysis.

Subdiscipline: 
Corequisites: 
Course Level: 
Implementation Notes: 

This activity can be used as an introduction to fundamental organometallic reactions and/or catalytic cycles. Students should work in small groups of 3-4.  Student must already be able to count electrons in an organometallic complex.

10 Jun 2016

George Stanley Organometallics

Submitted by Adam R. Johnson, Harvey Mudd College

This is an LO for the collection of organometallics LOs by George Stanley. Adam Johnson is curating the material that was written by George.

For many years, George hosted his organometallics lecture notes, powerpoint slides, and handouts, on his personal website at LSU. He always wanted that material available to the public. Recently, they moved to a CMS and that material is no longer available. Adam is working with George to get the 2016-2017 version of his materials up on VIPEr for everyone to use.

The lecture notes are freely available to all.

Subdiscipline: 
Prerequisites: 
Corequisites: 
Course Level: 
28 Sep 2015

Working with Catalytic Cycles

Submitted by Matt Whited, Carleton College
Evaluation Methods: 

Informal evaluation during group work and during group presentations

Evaluation Results: 

I most recently used this LO in the early weeks of a dedicated "Organometallic Chemistry" course after a fairly brief introduction to reaction mechanisms, as a way of transitioning to catalysis.  The students performed well on activity, easily completing the "fill-in-the-blank" problems, though they struggled a little more on the free response questions.  In particular, some groups needed help in assigning the role of HI in the Monsanto process.

Overall, this activity did a much better job than lectures I have used in past years to introduce catalysis.  Students identified key points where catalysis can be interrupted and factors to consider when thinking about overall rates and side products.

Description: 

Students work in groups to identify relevant steps and intermediates in 3 catalytic cycles, all the while considering bonding (and electron counting) factors.  Following assignment of these steps and intermediate species, the students consider several questions related to catalysis more broadly, particularly the role of each reagent, how to speed up or slow down specific steps, and the importance of regiospecificity in certain steps.

Learning Goals: 
  • Students will be able to apply knowledge of fundamental organometallic reaction classes to put together a catalytic cycle
  • Students will be able to consider the interplay of different steps and chemical species during catalysis, including structural factors allowing certain steps to occur
  • Students will be able to explain the role of accessible species not directly on the catalytic cycle and how these relate to the desired catalysis
Corequisites: 
Course Level: 
Subdiscipline: 
Implementation Notes: 

Students worked in groups of 3-4, allowing me to circulate and help groups as they came upon problems.  After allowing sufficient time for their work (maybe 15 minutes), I had groups present their answers for discussion by the class.

Time Required: 
30 minutes
16 Sep 2015

Iron Cross-Coupling Catalysis

Submitted by Laurel Goj Habgood, Rollins College
Evaluation Methods: 

Our proposed evaluation method is a written report in the style of an Inorganic Chemistry communication.  Instructors may choose an alternative method, such as an oral presentation, that is more appropriate for their class.

Evaluation Results: 

This experiment will be piloted during the 2015-2016 school year.  Evaluation results are forthcoming.

Description: 

In this experiment, students will synthesize and characterize an iron complex followed by completion of two series of catalytic cross-coupling reactions mimicking the methodology utilized by organometallic chemists to balance catalyst efficacy and substrate scope.  Initially the complex Fe(acac)3 [acac =  acetylacetone] is prepared.  Two sets of catalytic reactions are completed: one comparing different iron catalysts (Fe(acac)3, FeCl2, FeCl3) while the other compares substrates (4-chlorotoluene, 4-chlorobenzonitrile, 4-chlorotrifluorotoluene). This experiment was designed during the June 2015 “Improving Inorganic Chemistry Pedagogy” workshop funded by the Associated Colleges of the South.

Corequisites: 
Learning Goals: 

●      Prepare Fe(acac)3 and perform appropriate characterization.

●      Develop skills in manipulating chemicals in an air-free environment.

●      Determine efficacy of catalytic reactions (% product) using appropriate analytical technique

●      Provide explanations for differences in product yields grounded by inorganic theory

Equipment needs: 

FT-IR spectrometer

GC, GC/MS, or NMR spectrometer

Air-Free equipment to maintain nitrogen-environment 

Implementation Notes: 

This experiment will be piloted during the 2015-2016 school year.  As we collect data we will post additional information regarding experimental details and evaluation methods.  We welcome others in the VIPEr community to help us test this!  If you do try this, consider filling out the evaluation file attached and sending to lhabgood@rollins.edu.

Students will synthesize and characterize the iron complex individually.  Each student should complete an appropriate subset of the catalytic reactions such that the pooled class data has each catalytic reaction replicated in triplicate.  The Fe(acac)3 complex is commercially available so it is possible to complete the lab in two sessions if students are provided with all three catalysts initially.

Time Required: 
Three 3-hour lab sessions: (1) Synthesize iron complex, demonstrate air-free techniques, (2) Perform catalytic reactions with appropriate analysis for product yield, (3) Complete catalytic reactions with appropriate analysis for product
6 Jul 2015

Kinesthetic Learning: Cyclic Voltammetry Mechanisms

Submitted by Chip Nataro, Lafayette College
Evaluation Methods: 

I have only used this at the workshop. I do not anticipate teaching this material in class, so I doubt I will get any evaluation data. Perhaps the participants will comment on the effectiveness of this LO.

Description: 

This activity was created as part of a primer on cyclic voltammetry for the 2015 TUES workshop. The activity is designed to have one person represent the potential and several other people represent the molecules in solution. By simply scanning (walking through the line of people) and shaking hands, several simple mechanisms can be illustrated. The use of a joy buzzer with the first hand shake is highly encouraged, but not at all necessary. It adds a bit of levity to a serious topic and the author highly encourages using the joy buzzer on a "volunteer" that promised muffins years ago and has yet to deliver on said promise.

Learning Goals: 
  • A student will visualize simple cyclic voltammetry mechanisms with a kinesthetic experience.
  • A student will explain possible outcomes for single molecules upon oxidation or reduction. 

 

Prerequisites: 
Course Level: 
Corequisites: 
Equipment needs: 

Students

A joy buzzer (picture included in case you are unfamiliar with this object) is optional, but certainly fun.

Subdiscipline: 
Related activities: 
Implementation Notes: 

The idea behind this LO is for students to be able to visualize some of the possible outcomes of a species upon oxidation or reduction. It requires the instructor to select several students (4-6) to participate. The instructor and the students huddle before each demonstration so the students know how to behave. The slides that accompany this LO are used to show what the actual CVs look like after performing the visualization with student volunteers. The following instructions are also summarized in the notes on the slides.

In the case of a reversible system, the instructor (potential) walks past a line of students shaking their hands. The students turn 180 degrees upon shaking hands. When the instructor reaches the end of the line, they turn around and repeat the process in the opposite direction. In an irreversible system, after shaking hands, the students can do any number of thing to represent a chemical reaction taking place, the products of which are electrochemically silent. This could be putting their hands behind their backs, linking hands with another student, or anything else. Upon sweeping back through the line, the instructor discovers no hands to shake. In the third example, the instructor goes through the line very slowly the first time. This gives some of the students time to do something (grasp each other's hands for example) after having getting a hand shake. Not all of the students should undergo this reaction, so some of the students are available to shake hands upon reversing the scan. The second time, the instructor should sweep through fairly quickly so that the students don't have time to form another product. I encouraged my participants to make dramatic movements when I did the slow scan. In the final mechanism, upon shaking hands students were instructed to turn around and lift their hands up for a high five. This showed that an electroactive species was present, but it was somehow different from the starting material.

The joy buzzer is completely optional, but it was great fun. The person I did it to was not at all expecting it. It is electrochemistry after all, there should be a little shock.

Time Required: 
5-10 minutes
2 Jul 2015
Evaluation Methods: 

Students can hand in tthe first set of questions as homework which may be evaluated.  Class participation and group work may also be graded appropriately.

Evaluation Results: 

This is an untested LO.

Description: 

This learning object is based on discussion of the literature, but it follows a paper through the peer review process.  Students first read the original submitted draft of a paper to ChemComm that looks at photochemical reduction of methyl viologen using CdSe quantum dots.  There are several important themes relating to solar energy storage and the techniques discussed, UV/vis, SEM, TEM, electrochemistry, and catalysis, can be used for students in inorganic chemistry.

Unlike a typical literature LO where students discuss only the current science, this LO contains the actual reviewer comments to the original submitted manuscript as well as a link to the final version that was published in Journal of Materials Chemistry A.

DOI: 10.1039/C5TA03910J

Prerequisites: 
Learning Goals: 

Students will be able to...

·  Communicate the main ideas of a scientific research paper to classmates.

·  Identify the research area, importance of the research, and background information provided in a scientific paper.

·  Discuss areas of a paper that may be improved through revision.

·  Compare their views of necessary revisions with actual anonymous reviewers on a scientific paper and the eventual publication.

·  Understand the importance and shortcomings of the peer review process using an actual publication from the literature.

Implementation Notes: 

The LO has multiple sections which may be discarded or edited depending on the particular learning goals desired.  While the chemistry may be difficult for lower level students, the discussion of the peer review process may be valuable to students across multiple levels and even in writing courses.  Also provided are the authors' actual responses to the reviewers comments.  It should also be noted that the original article was submitted to ChemComm, but the subsequent revised article was submitted and accepted to Journal of Materials Chemistry A.

Time Required: 
Homework Assignment + 1 h in class
2 Jul 2015
Evaluation Methods: 

The assignment can be graded at the conclusion of the class period and then revisited at points later on an exam or at the final.  

Description: 

This question set has students examine the kinetics of the electrocatalytic reduction of CO2 to CO described in Sampson, D.L.; Nguygen, D., Grice, K.A.; Moore, C.E.; Rheingold, A.L.; Kubiak, C.P. Manganese Catalysts with Bulky Bipyridine Ligands for the Electrocatalytic Reduction of Carbon Dioxide:  Eliminating Dimerization and Altering Catalysis.  J. Am. Chem. Soc. 2014, 136, 5460-5471. 

Learning Goals: 

Students will be able to...

  • Identify the experimental conditions required for the pseudo-first-order kinetics assumption to be valid.
  • Compare and contrast electrochemical and chemical kinetics.
  • Apply given experimental data to deduce the reaction order with respect to all reactants in the electrocatalytic reduction of CO2.
  • Calculate the rate constant (kcat) for a given set of conditions.
Corequisites: 
Equipment needs: 

Students should have access to a computer with Microsoft Excel.  

 

 

Implementation Notes: 

This can be adapted to a general chemistry/introductory class or can be used as in-class discussion with upper level students.  Secondarily this can be given as a homework asssignment and then used in class as a discussion or as an in-class acctivity.  

 

 

Time Required: 
one 50 minute class
2 Jul 2015
Evaluation Methods: 

Students will be evaluated on preparation and participation using the attached evaluation form.

Evaluation Results: 

This is a new learning object created at the 2015 Summer VIPEr workshop and not yet been implemented. Results will be added by the creators after use in a class.

Description: 

This Learning Object involves reading a recent scientific journal article, answering questions relating to the content, and participating in a classroom discussion. The paper under review is “Regeneration of an Iridium (III) Complex Active for Alkane Dehydrogenation Using Molecular Oxygen,” Organometallics, 33, 1337-1340. DOI: /10.1021/om401241e). This paper presents a summary of results from experiments relating to important recent advances in organometallic chemistry, including alkane dehydrogenation and using as an oxidant to regenerate the active form of a catalyst.

 

Corequisites: 
Course Level: 
Learning Goals: 

After completing this literature discussion, students should be able to:

  • explain in 1-2 sentences the relevance/importance/rationale of a paper and what the conclusions are

  • interpret proton NMR spectra in the context of the paper

  • explain from the standpoint of the thermodynamic principles why the uphill transformation from alkane to alkene in this case is possible and non-reversible

  • count electrons in transition metal complexes and identify oxidation states and oxidized and reduced species
  • integrate their chemical knowledge and be able to come up with a reasonable answer to “what is the next step?” in the context of this paper

Implementation Notes: 

Give the hand out (or post the assignment online) to students ~1 week before the class period assigned for the discussion, with the following instructions: “Please go to the ACS website and find and download a copy of the paper. Print it out and as you read the paper, make notes on the paper and bring these to class with you. We will be using this paper to answer the following questions:” Alternatively, the paper could be downloaded by the instructor and either emailed or handed out to the students. In order to answer one of the questions, a table of thermodynamic values from the NIST website has been provided.

 

In order to reassure students who might be shy or hesitant about speaking up, students should be advised that they will not be graded on the correctness of the answer, but rather on their preparation and participation.

 

During the literature discussion, each student will be selected to answer a subset of the questions orally and/or on the board to start the discussion of that question. At the end of the literature discussion, the students will hand in the notes they have on each of the discussion questions, which they can edit during the discussion. The students be evaluated based on two criteria:

 

1.       Preparation: Did the students come to the discussion will thoughtful answers to the questions they were assigned?


2.       Participation: Did the students participate in the discussion of answers assigned to others? Did they communicate original ideas and questions clearly during the discussion?

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