Reaction mechanisms

14 Aug 2017

Chapter 14--Stanley Organometallics

Submitted by George G. Stanley, Louisiana State University
Description: 

Chapter 14 from George Stanley's organometallics course, Catalysis Introduction

 

this chapter covers an introduction to catalysis and includes many questions directly from the literature.

The powerpoint slides contain answers to some of the in-class exercises, so those are behind the "faculty only" wall. I share these with students after the class, but not before.

Everyone is more than welcome to edit the materials to suit their own uses, and I would appreciate being notified of any mistakes that are found.


Course Level: 
Subdiscipline: 
Corequisites: 
14 Aug 2017

Chapter 13--Stanley Organometallics

Submitted by George G. Stanley, Louisiana State University
Description: 

Chapter 13 from George Stanley's organometallics course, Migratory Insertion and Elimination

 

this chapter covers migratory insertion and elimination reactions.

The powerpoint slides contain answers to some of the in-class exercises, so those are behind the "faculty only" wall. I share these with students after the class, but not before.

Everyone is more than welcome to edit the materials to suit their own uses, and I would appreciate being notified of any mistakes that are found.


Subdiscipline: 
Corequisites: 
Course Level: 
14 Aug 2017

Chapter 12--Stanley Organometallics

Submitted by George G. Stanley, Louisiana State University
Description: 

Chapter 12 from George Stanley's organometallics course, Oxidative Addition and Reductive Elimination

 

this chapter covers oxidative addition and reductive elimination reactions.

The powerpoint slides contain answers to some of the in-class exercises, so those are behind the "faculty only" wall. I share these with students after the class, but not before.

Everyone is more than welcome to edit the materials to suit their own uses, and I would appreciate being notified of any mistakes that are found.


Subdiscipline: 
Corequisites: 
Course Level: 
14 Aug 2017

Chapter 11--Stanley Organometallics

Submitted by George G. Stanley, Louisiana State University
Description: 

Chapter 11 from George Stanley's organometallics course, Ligand Substitution

 

this chapter covers ligand substitution reactions.

The powerpoint slides contain answers to some of the in-class exercises, so those are behind the "faculty only" wall. I share these with students after the class, but not before.

Everyone is more than welcome to edit the materials to suit their own uses, and I would appreciate being notified of any mistakes that are found.


Subdiscipline: 
Corequisites: 
Course Level: 
3 Jun 2017

Introduction to Agostic Interactions

Submitted by Emma Downs, Fitchburg State University
Description: 

A brief introduction to agostic interactions and their importance to common organometallic mechanisms such as beta-hydride elimination. Examples of compounds containing these interactions are discussed and compared to familiar molecules such as diborane. Ways to characterize these interactions are also introduced.

Slides are based on the PNAS review Agostic Interactions in Transition Metal Compounds 

Brookheart, Green, and Parkin Proc. Natl. Acad.Sci. 2007104(7), 6908-6914

 

 
Course Level: 
Corequisites: 
Learning Goals: 

Define an agostic interaction and relate it to other types of bonding.

Provide examples of how the presence of an agostic interaction can be determined experimentally and through computational methods. 

 

Implementation Notes: 

This LO was developed at the VIPEr 2017 workshop at Franklin and Marshall College so it has not yet been implemented. The authors believed that implementation of this LO is best for an inorganic course that is post-organic, post-spectroscopy. It could be helpful after a discussion of 3-center 2-electron bonding and/or Lewis acidity/basicity. A literature discussion on an interesting agostic interaction with silicon was developed in conjunction with this LO and would be appropriate after discussing this five slides about LO.

Time Required: 
20 minutes
3 Jun 2017

An ion exchange method to produce metastable wurtzite metal sulfide nanocrystals

Submitted by Janet Schrenk, University of Massachusetts Lowell
Evaluation Methods: 

Evaluation methods are at the discretion of the instructor. For example, you may ask students to provide written answers to the questions, evaluate whether they participated in class discussion, or ask students to present their answers to specific questions to the class.

Description: 

In this literature discussion, students use a paper from the literature to explore the synthesis, structure, characterization (powder XRD, EDS and TEM) and energetics associated with the production of a metastable wurtzite CoS phase. Students also are asked define key terms and acronyms used in the paper; identify the goal of the experiments and determine if the authors met their goal. They examine the fundamental concepts around the key crystal structures available.  

 

Preserving Both Anion and Cation Sublattice Features during a Nanocrystal Cation-Exchange Reaction: Synthesis of a Metastable Wurtzite-Type CoS and MnS

Powell, A.E., Hodges J.M., Schaak, R.E. J. Am. Chem. Soc. 2016, 138, 471-474.

http://pubs.acs.org/doi/abs/10.1021/jacs.5b10624

 

There is an in class activitiy specifically written for this paper. 

Corequisites: 
Prerequisites: 
Learning Goals: 

In answering these questions, a student will be able to…

  • define important scientific terms and acronyms associated with the paper;

  • describe the rocksalt, NiAs, wurtzite, and zinc blende in terms of anion packing and cation coordination;

  • differentiate between the structure types described in the paper;

  • explain the difference between thermodynamically stable and metastable phases and relate it to a free energy diagram; and

  • describe the structural and composition information obtained from EDS, powder XRD, and TEM experiments.

Implementation Notes: 

This learning object was created at the 2017 IONiC Workshop on VIPEr and Literature Discussion. It has not yet been used in class.

Time Required: 
50 minutes
3 Jun 2017

Quantum Dot Growth Mechanisms

Submitted by Chi Nguyen, United States Military Academy
Evaluation Methods: 

The question document attempted by students in preparation for the literature discussion will be due prior to the in-class discussion. In particular, students' performance on the particle-in-a-box question will be evaluated to assess retention from the previously covered course material. The next exam following the discussion will contain specific question(s) (data/figure analysis) addressing these topics. Students' performance difference between the two will be evaluated. The extent to which students improve their post-discussion understanding of the concepts will direct future implementation.

Evaluation Results: 

To be determined. This is a newly proposed literature discussion.

Description: 

This literature article covers a range of topics introduced in a sophomore level course (confinement/particle-in-a-box, spectroscopy, kinetics, mechanism) and would serve as a an end-of-course integrated activity, or as a review activity in an upper level course. The authors of the article employ UV-vis absorption spectroscopy of CdSe quantum dots as a tool to probe the growth mechanism of the nanoparticles, contrasting two pathways.

 

Reference:  DOI 10.1021/ja3079576 J. Am. Chem. Soc. 2012, 134, 17298-17305

 
Corequisites: 
Prerequisites: 
Learning Goals: 

Apply the particle in a box model to interpret absorbance spectra with respect to nanoparticle size.

 

Analyze the step-growth and living chain-growth mechanisms proposed in this paper.

 

Evaluate the kinetics as it applies to the step-addition.

 

Recognize and apply multiple scientific concepts in an integrative manner.
Implementation Notes: 

Sophomore level implementation:  Recommend focusing on select portions (e.g. Figures 1b, 2, 5 with corresponding text) of the paper rather than having students read the entire document.  The learning objects focus on select topics, such as particle-in-a-box, reaction mechanism, and kinetics in conjunction with absorbance spectroscopy.  This would be a good literature discussion resource for an end-of-course integrative experience that encompasses multiple topics from general chemistry and inorganic chemistry.  

 

Advance level implementation:  For an upper division course, incorporate the paper in its entirety early in the course as an assessment on students’ ability to integrate multiple concepts that they should have learned in general chemistry, organic chemistry, and physical chemistry.  To enhance the experience, accompanying the literature discussion on this paper with a laboratory experience by repeating the experimental and characterization procedures presented in the paper, and having students' compare their results with published results.  This also serves to enhance students’ scientific literacy by critically assessing the quality of the paper.

 

Excerpts of the paper and questions can be used on a graded event, or as lesson preparation for in class discussion.

 
Time Required: 
In-class discussion takes approximately 50 minutes with students having already read the paper and submitted their responses to the questions.
23 May 2017

Ligand based reductive elimination from a thorium compound

Submitted by Chip Nataro, Lafayette College
Evaluation Methods: 

This was developed after the semester in which I teach this material. I look forward to using it next fall and I hope to post some evaluation data at that point.

Description: 

This literature discussion is based on a paper describing the ligand-based reductive elimination of a diphosphine from a thorium compound (Organometallics2017, ASAP). The thorium compound contains two bidentate NHC ligands providing an opportunity to discuss the coordination of these ligands. The ligand-based reduction is very subtle and would be challenging for students to pick up without some guidance. The compound undergoing reductive elimination also presents an excellent introduction into magnetic nonequivalence and virtual coupling. In addition, the compounds presented in this paper provide the opportunity to do electron counting on f-block compounds. 

Prerequisites: 
Corequisites: 
Learning Goals: 

Upon completing this LO students should be able to

  1. Use the CBC method to count electrons in the thorium compounds in this paper
  2. Describe the bonding interaction between a metal and a NHC ligand
  3. Discuss magnetic nonequivalency and virtual coupling
  4. Describe ligand-based reductive elimination and rationalize how it occurs in this system
Course Level: 
Time Required: 
50 minutes
11 Apr 2017

Johnson Matthew Catalytic Reaction Guide

Submitted by Sheila Smith, University of Michigan- Dearborn
Evaluation Methods: 

No evaluation yet

Evaluation Results: 

No results yet

Description: 

This guide, available in print, online and in an app, allows users to look up appropriate catalysts and conditions to accomplish a wide variety of reactions.

 

Prerequisites: 
Course Level: 
Learning Goals: 

A student should be able to use the Catalytic Reaction Guide (CRG) to identify appopriate reaction conditions and catalysts to accomplish a wide variety of reactions.

Implementation Notes: 

I have not yet used this... I just picked up a copy at ACS, but will add to this as I implement it in my classroom.

 

Time Required: 
variable
27 Mar 2017

Nanomaterials for Carbon Dioxide Reduction

Submitted by Anne Bentley, Lewis & Clark College
Evaluation Methods: 

The problems presented here represented half the points on the final exam – I have included point totals to give an idea of the weight assigned to each problem.

Evaluation Results: 

Twelve students were enrolled in my course in the fall 2016. The average overall score for these problems was 78%.

For problem 1b, I calculated the oxidation numbers using the familiar general chemistry method of assigning oxygen as –2 and hydrogen as +1. Students recently coming through organic may have some other way to do it, and you may need to provide directions for your students about your preferred method.  I think I could have worded part (c) better to try to emphasize the redox processes involved. I wanted them to think of combustion, but I think they needed to be specifically prompted, such as "Give an example of the combustion processes that generate CO2 and trace the oxidation state of carbon through the reaction." Overall my students scored 86% on problem 1.

The second problem (about another method that could be used to measure d-spacing) was fairly hit or miss.  Five students got full credit, six students got 3 points, and one got zero. Eleven out of twelve did answer part (a) correctly.  I realized as I made this LO that the article says the carbon-based material doesn’t diffract X-rays, but doesn’t actually directly explain whether or not the Cu nanoparticles diffracted X-rays, so you may need to adjust the question to be technically accurate.

Question three (re: surfactants in nanoparticle synthesis) referred back to knowledge from earlier in the course. The overall score was 61%.

Question 4 (define and describe electrodes) was fairly straightforward, and students scored 85%.

Question 5 caused some confusion, as some students missed that I was looking for “carbon-containing” products only. I didn’t count off for that mistake, but it made the problem harder for students who included hydrogen in each box.  Overall, students did very well on this problem (89% correct).

Question 6 – again, not too much trouble here (84% correct).

Question 7 – I was surprised that students didn’t do better on this question, as I thought that water reduction was mentioned often in the article.  Only three (of 12) students scored 5 points on this problem, and the average score was 53%.  This was probably my favorite question, as it foreshadows electrochemistry topics I cover in my inorganic course.

Description: 

This literature discussion is based on an article describing the use of copper nanoparticles on an N-doped textured graphene material to carry out the highly selective reduction of CO2 to ethanol (Yang Song et al., “High-Selectivity Electrochemical Conversion of CO2 to Ethanol using a Copper Nanoparticle / N-Doped Graphene Electrode” ChemistrySelect 2016, 1, 6055-6061.  DOI: 10.1002/slct.201601169). The article provides a good introduction to the concepts of electrochemical reduction, selectivity and recycling of fossil fuels. The literature discussion assignment shared here was used as half of the final exam in a half-credit nanomaterials chemistry course, but could be adapted for use as a take-home or in-class assignment.

Corequisites: 
Course Level: 
Learning Goals: 

After reading this paper and working through the problems, a student will be able to:

  • assign oxidation states to carbon and trace the oxidation and reduction of carbon through fossil fuel combustion and CO2 conversion
  • describe the role of control experiments in studying the CO2 conversion presented in the article
  • define the word “selective” in the context of this research
  • use the proposed mechanism to explain why the electrode studied produces ethanol in such a high proportion
  • identify the primary reaction competing with CO2 reduction for available electrons
Implementation Notes: 

These questions comprised half of the final exam for my half-credit nanomaterials chemistry course in the fall of 2016.  I gave the article to the students one week ahead of time. They were encouraged to read the article, make any small notes they liked, and meet with me in office hours with questions. At the final exam they were allowed to use their copy of the article, but they were also required to hand in their copy with their exam so that I could make sure they hadn't written lots of extraneous information on the exam copy.

The nanomaterials course features near-weekly homework assignments centered around articles from the literature. Because I used this article at the end of the course, students were already familiar with nanomaterials synthesis and characterization techniques. Thus, some of the questions I asked relied on previous knowledge. 

Please feel free to adapt these questions and add some of your own. Leave comments describing any new questions you’ve added.

Time Required: 
one hour

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