Physical methods / analytical techniques

10 Jun 2020

A copper "Click" catalyst for the synthesis of 1,2,3-triazoles

Submitted by Chip Nataro, Lafayette College
Evaluation Methods: 

I have not used this in class yet, but anticipate updating this after the fall 2020 semester. This comes as a result of the June 9th LO party.

Description: 

This paper (Gayen, F.R.; Ali, A.A.; Bora, D.; Roy, S.; Saha, S.; Saikia, L.; Goswamee, R.L. and Saha, B. Dalton Trans2020, 49, 6578) describes the synthesis, characterization and catalytic activity of a copper complex with a ferrocene-containing Schiff base ligand. The article is relatively short but packed with information. However, many of the details that are assumed knowledge in the article make for wonderful questions some of which I hope I have captured. The LO includes electron counting using the CBC method, d-orbital splitting, Latimer diagrams and interpretation of catalytic results. There are also opportunities to discuss green chemical practices.

Corequisites: 
Prerequisites: 
Course Level: 
Learning Goals: 

A student should be able

determine the electro count and metal valence in the catalyst

use group theory to determine the number of IR active vibrations in the catalyst

discuss green chemical principles in relation to this article

interpret data from tables and draw conclusions from that data

suggest an additional catalytic experiment that could be performed

Implementation Notes: 

I like the question invoking a Latimer Diagram to get students to rationalize why the copper(I) active catalyst was not isolated. I also enjoyed sneaking in a group theory question. But my favorite quesiton is the last one in which students are asked to go beyond what it presented in the paper and suggest another catalytic reaction to perform. There are some aspects of the paper that were not covered in-depth. In particular the XPS seemed to be a rabbit hole I opted not to go down. The authors do not go into great detail on this topic and perhaps there is a question that could be included, but I opted not to. I also opted not to include anything about the bonding in ferrocene which can be found in many of my other LOs. Also on this list one might include UV-Vis spectroscopy and the computational studies.

Time Required: 
50 minutes
9 Jun 2020

Gold carbonyl complexes

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

the first 3 problems are skill practice. The fourth problem is tough and would lead natrually to an in class discussion of bonding models, and how theories change over time.

Evaluation Results: 

I don't have any, unfortunately. 

Description: 

I've been meaning to write an LO on non-classical metal carbonyl complexes for a long time. This paper describes the synthesis and characterization of a gold carbonyl prepared in superacidic media. The LO asks the students to do some relatively straightforward reduced mass calculations to predict the 13C labeled CO stretch from the unlabeled one, but then asks the students to think about /why/ the Au-CO stretch is /higher/ than that of free CO.

Learning Goals: 

Students will practice using reduced mass calculations to calculate labeled stretching frequencies

Students will practice the Dewar-Chatt-Duncanson model of bonding

Students will use an MO diagram and their understanding of MOs to answer the question as to why the CO stretch in a non-classical carbonyl is higher than that of free CO

 

Equipment needs: 

none

Corequisites: 
Course Level: 
Implementation Notes: 

This is billed as an in-class activity because the fourth question is quite difficult. I assigned it as a challenge homework problem during the COVID semester (Spring 2020) but no one did it as far as I can tell. 

Time Required: 
30 minutes with time for discussion at the end
6 Apr 2020

Migratory Insertion Guided inquiry

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

I look to see if students are able to 

1) determine the correct number of IR stretches for the compounds,

2) calculate the labeled IR stretches from the unlabeled ones,

3) correctly predict the product distributions expected for the 3 mechanistic pathways

4) understand/explain the importance of experiment 2, negative evidence, and microscopic reversibility

Evaluation Results: 

Awaiting assessment data at time of submission; will add ASAP.

based on 3 complete submissions (43% response rate, due to COVID)

students generally had no problems with questions 1 and 2, and were able to determine the number/symmetry of IR stretches using group theory, and to predict a vibrational frequency from a areduced mass calculation.

question 3 gave them a lot of trouble. I would normally do this as an in-class exercise and be able to talk them thorugh problems. students were able to draw some of the correct products for the various mechanisms but did not understand the fact that there would be a statistical distribution of products based on the 13C label. However, I spoke with all 3 students and they said that after priming their brains with the exercise, the reading in the textbook made a lot of sense and they understood what they had missed. Perfect!

Students did not generally understand the concept of negative evidence as hoped.

For future years, if I were unable to do this exercise in class, I would want to provide more guidance to get students to think about product distribution. However, if done in class, I think that watching them struggle a bit before helping them over the hurdle would be good.

Description: 

The migratory insertion reaction is one of the "four" main reactions in organometallic chemistry. It involves the formation of an acyl group by insertion of a CO molecule into a metal alkyl bond. The reaction is sometimes called the carbonyl insertion reaction because the product appears to be a result of direct insertion of the CO into the metal alkyl, but that name implies a mechanistic pathway that may not be in operation.

The reaction of methyl pentacarbonyl manganese(I), MeMn(CO)5, was studied extensively by Calderazzo in the mid 1960s. The use of C13 labeled CO and IR spectroscopy allowed for the identification of the mechanism for the reaction among the likely possibilities of direct insertion, alkyl migration, or carbonyl migration. This guided inquiry exercise presents some of the data from the Calderazzo paper and has students interpret it to determine the mechanism of the reaction in this system.

It should be noted that there are examples of all three mechanisms operating in different chemical systems, so this exercise is specific to the manganese substrate, though it is usually more generally applied.

Learning Goals: 

Students will interpret and analyze IR data of metal carbonyls

Students will calculate IR bands for 13C labeled peaks in the IR

Students will predict product distributions for the three likely mechanisms (direct insertion, carbonyl migration, alkyl migration).

Students will compare expected and observed product distributions and identify the mechanism operating

Students will discover and discuss the concept of "negative evidence."

Equipment needs: 

none

Prerequisites: 
Corequisites: 
Subdiscipline: 
Course Level: 
Implementation Notes: 

In my course, we usually cover isotopic labeling and its application to IR spectroscopy. We also use group theoretical methods to predict and assign M-CO stretches the correct symmetry labels and whether they are IR active or not. These two factors could be removed from the guided inquiry and presented as additional data to the students if you don't cover these topics. The rest of the activity is self contained. Access to the paper is not required, as the IR bands are in the document but a reference is provided.

Time Required: 
30-50 minutes
21 Mar 2020

chromium and molybdenum arene complexes (COVID-19 version)

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

i have no idea.... yet! (growth mindset!)

Evaluation Results: 

I will report this later this spring.

Description: 

The synthesis of (arene)Cr(CO)3 and (arene)Mo(CO)3 complexes are fairly standard experiments in the organometallic curriculum. I present here some student data and experimental descriptions of real procedures carried out at Harvey Mudd College over the previous two to three years. The word document has the answers in it so it is posted under "faculty resources" but the raw data (pdf or png form) is presented for those who need data to support their distance learning classrooms in the Spring of 2020. I also include an input file for Mo(benzene)(CO)3 should you desire to use WebMO or Gaussian to carry out some calculations. 

 

there was a minor mistake in the reported integrations for one of the complexes in the original faculty only file; it has been fixed in the v2 version.

Course Level: 
Prerequisites: 
Corequisites: 
Learning Goals: 

Students will interpret provided data to write their own experimental sections for molecules they were unable to prepare in the lab. The guided inquiry part allows students to use data to predict the outcome of a chemical reaction.

Equipment needs: 

be able to view PDF/PNG files

Implementation Notes: 

I have not used this yet but will be using it spring 2020.

Time Required: 
unknown
21 Mar 2020

Ferrocene acylation - The Covid-19 Version

Submitted by Chip Nataro, Lafayette College
Description: 

This is the classic Chromatography of Ferrocene Derivatives experiment from "Synthesis and Technique in Inorganic Chemistry" 3rd Ed. (1986 pp 157-168) by R. J. Angelici. There are no significant changes from the experiment published in the book so details will not be provided. What is provided are links to some excellent videos showing the experiment and characterization data for students to work with. For the time being this will be a living document. Currently it has 1H, 13C{1H}, COSY, DEPT, HMBC, HSQC IR, UV-Vis, GC-MS and Cyclic Voltammetry raw data files for all compounds for students to work with. It also includes processed 1H, 13C{1H}, COSY, DEPT, HMBC, HSQC, IR, GC-MS and Cyclic Voltammetry data for all compounds. If anyone has any additional means of characterization they would like to include (say Mossbauer) please feel free to contact the author.

Corequisites: 
Learning Goals: 

A student should get an appreciation for what doing this lab would be like by watching videos. In addition, the student will analyze the data provided and learn about the characterization of ferrocene, acetylferrocene and 1,1'-diacetylferrocene.

Equipment needs: 

Nothing.

The NMR data comes from a Bruker instrument and can be opened with TopSpin, MestReNova and perhaps other programs.

Implementation Notes: 

Like most everyone at this time this is going to be a trial by fire.

20 Mar 2020

setting up an air-sensitive reaction (video)

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

have not done

Evaluation Results: 

n/a

Description: 

This is a video I made to demonstrate the basics of air-sensitive reaction setup under nitrogen flush. It is the simplest, most basic method for setting up a reaction with air/water sensitive reagents.

The link goes to my channel on YouTube.

Corequisites: 
Subdiscipline: 
Learning Goals: 

After watching this video, a student will be able to set up a reaction under nitrogen. Or, if there is a global pandemic and the students are at home, they will at least see how it is done.

Course Level: 
Implementation Notes: 

I made this and am sharing it with my students because they did not get an opportunity to set up an air sensitive reaction this year.

Time Required: 
5 minutes to watch video
19 Mar 2020

Job's Method - The Covid-19 Version

Submitted by Chip Nataro, Lafayette College
Evaluation Methods: 

Students are generally asked to write a full lab report including an abstract, brief introduction, experimental and results/discussion. I will likely not ask them to do that in this virtual lab. However, they will be asked to determine the value for n for the various [Ni(en)x] solutions as well as questions 1 and 2 from Angelici's book. In addition, I typically ask them to do some literature searching questions, but I am not sure if they will have access to SciFinder so I may have to bypass that or provide them the original papers I have them look at. Links to those papers are included.

Evaluation Results: 

I'll use this in a few weeks and see how it goes.

Description: 

This is the classic Job's Method experiment from "Synthesis and Technique in Inorganic Chemistry" 2nd Ed. (1977 or 1986 pp 108-114) by R. J. Angelici. There are slight changes from the experiment published in the book but they just include running solutions with ethylenediamine mole fractions of 0.67 and 0.75, so details will not be provided. What is provided are a series of pictures and videos showing the experiment being performed. Also included are the raw files of the absorbance spectra in EXCEL. It is not perfect but given the situation many of us are facing at the time this is published, it is better than nothing.Note that this lab was updated on 4/4/2020. The previous data was terrible. New solutions using a fresh bottle of ethylenediamine were prepared. The two solutions mentioned previously were also included. The data is much better. The worked up data has also been included in the instructor only files.

My apologies to my coauthors who spent way too much time looking over the original data set and trying to make sense of it. Their thoughts and insight led to this update. My sincere apologies to anyone else that scuffled over the original data.

Prerequisites: 
Corequisites: 
Course Level: 
Learning Goals: 

A student should get an appreciation for what doing this lab would be like by watching videos. In addition, the student will analyze the data provided and determine the species present in solutions containing various mole fractions of ethylenediamine and Ni(II).

Equipment needs: 

Nothing

Implementation Notes: 

Like most everyone at this time this is going to be a trial by fire.

9 Oct 2019

2019 Nobel Prize - Li-ion battery LOs

Submitted by Barbara Reisner, James Madison University

Congratulations to the 2019 recipients of the Nobel Prize - John B. Goodenough, M. Stan Whittingham and Akira Yoshino. It's a well deserved honor!

There are several LOs on VIPEr that talk about lithium ion batteries and related systems. The 2019 Nobel is a great opportunity to include something about these batteries in your class.

I hope to see more LOs in the coming weeks so we can bring this chemistry into our classrooms!

Prerequisites: 
Corequisites: 

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