Synthesis and reactivity

2 Apr 2008

Fluoro Analogue of Wilkinson's Catalyst

Submitted by Maggie Geselbracht, Reed College
Evaluation Methods: 
Student performance on the discussion questions is assessed.
Description: 
This paper describes the synthesis and characterization of the fluoro analogue of Wilkinson's catalyst [(Ph3P)3RhF]. The fluorine for chlorine switch causes an interesting change in the reactivity, promoting activation of C-Cl bonds in chloroarenes. Discussion of this paper nicely pairs with the chemistry of Wilkinson's catalyst, highlighting periodic trends in bonding and reactivity.
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Implementation Notes: 
Students are asked to read the paper and answer the discussion questions before coming to class. These questions serve as a useful and hopefully accessible point to begin discussion of the paper.
Time Required: 
50 minutes
28 Mar 2008

Miessler and Tarr: Inorganic Chemistry, 3rd. Ed

Submitted by Nancy Scott Burke Williams, Scripps College, Pitzer College, Claremont McKenna College
Description: 

Miessler and Tarr is an inorganic textbook which is is best suited to an upper-division one-semester inorganic course, though there is more material than can be covered in a single semester, so some choice of topics is necessary.  It is very well suited for a course oriented around structure, bonding, and reaction chemistry of transition metal compounds, but is very limited in its treatment of solids, main-group, descriptive chemistry, and bioinorganic.  Pchem would be helpful but is not necessary.  In particular, the treatment of MO theory is very in-depth.  The quality of end-of chapter problems is generally good.  The book is fairly readable, giving it an advantage over some of the more "reference work" style textbooks, but as a result, is a less useful text to have on your bookshelf five years hence.  Pearson Higher Ed. suggests a retail price of $144.20.  

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28 Mar 2008

Zinc-Zinc Bonds

Submitted by Maggie Geselbracht, Reed College
Evaluation Methods: 
Student performance on the discussion questions is assessed.
Description: 
This paper in Science reports the synthesis of decamethyldizincocene, a stable compound of Zn(I) with a zinc-zinc bond. The title compound and the starting material, bis(pentamethylcyclopentadienyl)zinc, offer a nice link to metallocene chemistry, electron counting, and different modes of binding of cyclopentadienyl rings as well as more advanced discussions of MO diagrams. More fundamental discussion could focus on the question of what constitutes the evidence for a chemical bond, in this case, the existence of a zinc-zinc bond.
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Course Level: 
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Implementation Notes: 
Students are asked to read the paper and the accompanying Perspecitves article before class as well as answer the discussion questions. The questions serve as a useful starting point for class discussion. I also took this opportunity to introduce the MO diagram for ferrocene to illustrate the 18 electron rule.
Time Required: 
50 minutes
26 Mar 2008

Housecroft and Sharpe: Inorganic Chemistry, 3ed

Submitted by Lori Watson, Earlham College
Description: 

Housecroft and Sharpe (Inorganic Chemistry, 3ed): This is a comprehensive inorganic textbook designed primarily for students at the Junior/Senior level. P-Chem would not be needed as a prerequisite for this text, but would be helpful. It includes both theoretical and descriptive material along with special topics, enough for a two semester course though it is easily adaptable to a one-semester "advanced inorganic" course by choosing only some topics. It is written in a clear and generally readable style and the full-color graphic contribute to student understanding. Ancillaries include electronic versions of most figures, and a student site with a limited number of multiple choice review questions for each chapter. The 3rd edition updates the end-of -the-chapter problems, though disappointingly does not draw problems from the recent literature. In general, these are good review problems to make sure students understand the basic concepts, but some faculty will want to supplement student assignments with more challenging problems. The list price for the student text is $175 for a paperback, 1098p version.

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9 Mar 2008
Description: 
This is a literature discussion assignment which asks students to read and write responses to some guided questions.  This is then followed by an in-class discussion loosely based on the questions provided.  This particular article investigates the synthesis and structural characteristics of a calcium carbene.  Within the context of the journal article, I ask students to review MO diagrams and interpret X-ray data.  I also introduced computational methods in the context of inorganic chemistry using this paper.
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Time Required: 
2-3 hours for students beforehand; 50 minutes in class
9 Mar 2008
Evaluation Methods: 

Take home writing assignment and in-class discussion.

Evaluation Results: 

Students found the kinetics a bit difficult to follow, but "got it" after we went over it in class. They picked up on the catalytic cycle right away and came away with some good "suggestions" for future work.

Description: 

This is a literature discussion assignment in which students read a paper, come up with their own answers to the provided questions (and submit them).  This is followed by a general in-class discussion on the paper.  This particular article deals with hydrosilyation of carbonyl compounds by a Re catalyst and describes the mechanism and kinetics in detail.  I found it a good paper to help students connect their P-chem (and inorganic) kinetics with a "real" system.  As part of the literature assignment, I also ask students to draw an MO diagram of a simple substrate (for review).

Subdiscipline: 
Course Level: 
Learning Goals: 

Upon completing this LO students should be able to:

  1. read and extract information from a primary literature article
  2. develop the MO diagram for SiHCl3 using a fragment orbital approach
  3. interpret X-ray crystallographic data to explain bond distances and angles
  4. analyze kinetics data to understand reaction order and kinetic isotope effect for stoichiometric and catalytic reactions
  5. understand and explain how a reaction can be irreversible yet have labile ligands
     
Implementation Notes: 

Students who are currently enrolled in Thermodynamics and Kinetics may need to be paired with a student who has previously completed the course

Time Required: 
2-3 hours writing for students; 50 minutes in-class (could be shorter)
4 Jan 2008

Two Communications on Bioinorganic and Coordination Chemistry

Submitted by Hilary Eppley, DePauw University
Evaluation Methods: 
Could either grade participation in an in class discussion or collect the answers and grade them.
Evaluation Results: 
For this assignment, I like to break up a reasonably sized class into two groups, focusing their attention on one of the communications, but reading both of them. You could have the students complete the questions for one or both of the papers.
Description: 
This assignment would make a good choice for a first attempt at actually having a discussion on primary literature articles since these are two short communications. They also touch on two important applications of coordination chemistry so might be appropriate early in a course, namely modeling biological systems and non-linear optical applications.
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Time Required: 
2 h
4 Jan 2008

student choice experiment

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 
I typically have this assignment as one of 6 to 7 lab experiments that take place during the semester.  I grade on purity, yield, the proposal written by the student, and quality of presentation (when done).
Description: 

The students prepare a short proposal outlining their desired target and why they want to make it.  Chemicals are ordered, and during the last 3-4 weeks of the semester, the students carry out their synthesis.  The writeup is as a paper submtited to the journal Inorganic Chemistry using the template from the journal web page.

This is a favorite lab at HMC.  I increased the length of the experiment to 4 weeks from 2 weeks during 2007, allowing more time for exploration, optimization, and characterization of their products.  Past targets have inlucded Wilkinson’s catalyst, ionic liquids, Zr(ebthi)Cl2 (challenging), siloxane polymers (difficult to characterize).

 I highly recommend that students submit proposed syntheses early to get them approved.  The students are often either way too ambitious, or too tentative and want to make some simple thing from another lab manual.  I like them to do two linear steps (more for stronger students.)


Course Level: 
Prerequisites: 
Equipment needs: 
varies widely!
Implementation Notes: 
The lab is chaos.  Hire a TA for this experiment.  Students are running you ragged for the first 2 weeks in the lab, but it is a lot of fun. 
Time Required: 
3-4 weeks, more if student presentations are included
4 Jan 2008

Buchwald/Hartwig amination

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 

I would normally grade on purity and yield of the isolated compound, as well as experimental technique, but since we are still optimizing the conditions, I give students the benefit of the doubt.

Description: 

I wanted a modern organometallic experiment showing the utility of Pd for coupling reactions.  Students attempted a variety of reaction conditions during the spring of 2007 and 2008.  Eventually,  we were able to get the reaction to work with a variety of primary amines (linear, cyclohexylamine) and t-butylamine.  Yields are not great (40-80%) and this experiment needs some optimization.  However, products were observed by GC-MS and NMR.

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Equipment needs: 

This experiment is air-sensitive, but not enormously so.  The most sensitive reagent is the NaOtBu, which could be weighed in air in a pinch.  We use a glove box since we have one.  We store the Pd complexes under N2 after use.

 

Schlenk line, Ar balloons or glove box

Schlenk glassware, standard organic glassware

temperature controlled oil bath or heating mantle and thermometer.

Related activities: 
Implementation Notes: 

I usually turn off the students reactions after 18-24 hours, let them cool down, quench them with ether and store them in the 2-neck flasks until the following week where students work up the reaction and analyze by NMR and GC-MS.  We don't purify the compounds by column chromatography, but that could be added easily.

Time Required: 
1 to 2 3-4 hour lab sessions
17 Nov 2007

How to Read an Inorganic Paper for Synthesis Information

Submitted by Hilary Eppley, DePauw University
Evaluation Methods: 

I typically have this assignment worth about 25 points. I typically use the class when this is turned in as a discussion (could even have them bring two copies of answers to class) to get at some of the topics covered in this assignment. I always like to talk about some definitions, where to find certain information in the paper, sample answers to other questions (funding, productivity of author, types of characterization, etc.). Students turn in a copy of the paper with their assignment so that the instructor can check answers. Alternatively, you could assign one or two papers to the entire class. I just like talking about the differences in the discussion.

Evaluation Results: 

Most students do quite well on this assignment, generally earning 20-25 out of 25 on the assignment.   Things sometimes missed include not knowing what to do with solvents in writing the reactions, not identifying all of the characterization methods, or missing special conditions because they are described in the General Experimental Methods section at the beginning of the Experimental Section.   

Description: 

This assignment takes students through the process of learning how to find and read a paper from the primary literature, specifically to get experimental details (synthesis, characterization).  It also focuses on how to use a variety of chemical information resources.  It could be combined with the questions from Chemical Information Assignment to create a longer assignment.  

Prerequisites: 
Corequisites: 
Learning Goals: 

A student will analyze an inorganic paper to determine the goal of the research and analyze the experimental and discussion section of a paper to extract the following information:

  • Chemical reactions (with appropriate stoichiometric ratios)
  • Special conditions for reactions (such as air sensitivity, hydrothermal conditions)
  • Experimental techniques used to identify and characterize compounds
  • Special equipment needed

The discussion resulting from the assignment will allow the instructor to address terms that students did not understand and perhaps relate the discussion to future topics that will be covered in the class.  When  combined with the Chemical Information Assignment, it could also be used as an introduction to both finding structures, what else the author has written, and other chemical information.     

Course Level: 
Topics Covered: 
Time Required: 
about 1 1/2 hours for the students, 50 min in class

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