Molecular structure

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. 

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.

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" 3rd Ed. (1986 pp 108-114) 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 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. I was extremely rushed given that the governor essentially closed the state down the evening I did this, so please forgive any errors. This also includes literature searching questions.

Prerequisites: 
Course Level: 
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 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.

5 Dec 2019

Flipped Class Module - Lewis Structures of Industrially and Environmentally Relevant Molecules

Submitted by Jack F Eichler, University of California, Riverside
Evaluation Methods: 

1) Performance on the pre-lecture online quiz

2) Performance on the in-class activity (clicker scores or hand-graded worksheet)

 

Evaluation Results: 

Students generally score on average 70% or higher on the pre-lecdure quiz, and on average 70% or more of students correctly answer the in-class clicker questions. 

Description: 

This is a flipped classroom activity intended for use in a first semester general chemistry course. Students are expected to have prior knowledge in identifyng the difference between molecular and ionic compounds, understanding the conceptual framework for how covalent bonds form, and how to draw Lewis dot symbols for atoms, and how to determine the number of valence electrons for atoms.



The activity includes:

1) pre-lecture learning videos that guide students through learning how to draw valid Lewis structures, determining how to caculate the formal charge for atoms in molecular compuonds/Lewis structures, and using formal charge to determine which Lewis structure is most stable if multiple Lewis structures are possible for a given molecule;

2) pre-lecture quiz questions; and

3) an in-class activity that requires students to apply their knowledge of chemical bonding in drawing Lewis structures.

Acknowledgement: This material is based upon work supported by the National Science Foundation under Grant No. 1504989. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Learning Goals: 

Students should be able to:

a) draw Lewis structures of molecular compounds;

b) determine the formal charge of atoms in molecular compounds;

c) use formal charge to predict the most stable Lewis structure.

 

Equipment needs: 

Suggested technology:

1) online test/quiz function in course management system

2) in-class response system (clickers)

Course Level: 
Corequisites: 
Prerequisites: 
Implementation Notes: 

Attached as separate file. 

Time Required: 
50-80 minutes
9 Oct 2019

Fourier Transform IR Spectroscopy of Tetrahedral Borate Ions

Submitted by Zachary Tonzetich, University of Texas at San Antonio
Evaluation Methods: 

The students perpare laboratory reports displaying their data in proper format with each peak labeled. The report must also contain answers to all of the quetions posed in the manual. Student performance and learning is assessed by the qualtity of their written reports and by a separate quiz covering aspects of vibrational spectroscopy. Teaching assistans also ensure that students' data acquisition is performed in a satisfactory manner during the laboratory period.

Evaluation Results: 

Students typically have great difficulty connecting the idea of normal modes, their symmetries, and why we observe IR peaks. They approach IR spectroscopy in much the same way they do NMR spectroscopy (i.e. methane shows four equivalent C-H bonds so I expect one C-H stretching motion) leading to serious misconceptions. This laboratory was designed in part to dispell these misconceptions. Question 1 addresses this issue most directly and many of the class answer incorrectly.

The questions in the laboratory involving harmonic oscialltor analysis are generally more straightforward for students as they just need to use the correct equations. Most of the class answers these correctly.

Likewise, students generally understand that vibrational frequencies are inversely proportional to the mass of the atoms involved in the vibration and are there able to make connections between the observed spectra of BH4-, BD4- and BF4-.

Aspects of functional group analysis are more familiar to students and they generally have little trouble assigning the spectrum of tetraphenylborate.

Description: 

This experiment was developed for an upper division Instrumental Analysis course to give students additional experience with infrared (IR) spectroscopy beyond the routine functional group identification encountered in undergraduate Organic Chemistry courses. It shares some aspects with the analysis of gas phase rovibrational spectra typically performed in Physical Chemistry courses, but places a greater emphasis on more practical considerations including data acquisition (using ATR) and interpretation. The molecular ions used in the experiment also demonstrate tetrahedral symmmetry which allows for topics in Group Theory to be exploited.

The experiment has students record the spectra of several tetrahedral borate ions including the isotopomers NaBH4 and NaBD4. The students then analyze their data in the context of the symmetry of normal modes, the harmonic osciallator model, comparisons with Raman spectra, and functional group composition. Post lab questions guide students through each of the topics and ask them to make quantative and qualitative predictions based on their data and theoretical models of molecular vibration.

Course Level: 
Learning Goals: 

-Students should be able to understand the relationship between molecular structure, normal modes, and peaks in the IR spectrum. This is a major misconception with students as they tend to believe that the presence of four B-H bonds in the borohydride ion will neccessary mean that four peaks (or one since they are equivalent) will be observed by IR. Unlike NMR spectroscopy, there is no 1:1 correspondence between the number of equivalent bonds and the number of peaks observed in the spectrum.

-Students should also be able to apply their knowledge of theoretical models (quantum harmonic oscillator) to quantitaively intrepret IR spectra and predict the energy of transitions that cannot be observed due to instrumental limitations.

-Students should be able to understand at a qualitative level how the masses of atoms affect the energy of molecular vibrations.

Equipment needs: 

The only required piece of equipment beyond the chemicals is an infrared spectrophotometer. At our institution we use an ATR element to acquire the data, but KBr pellets or nujol mulls should work equally well. All chemicals were purchased from Sigma-Aldrich and are of reasonable price.

Implementation Notes: 

See attached file with more details. The data acquisition is very straightforward if ATR sampling is employed. Students need only use the instrument for about 15 - 20 minutes to record all four samples.

Time Required: 
30 minutes to 2 hr depending upon the number of students.
25 Jul 2019

1FLO: One Figure Learning Objects

Submitted by Chip Nataro, Lafayette College
Corequisites: 
9 Jun 2019

An improved method for drawing the bonding MO for dihydrogen

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

When I do this correctly, the students don't accidentally see something which may make immature students giggle.

Evaluation Results: 

I have had multiple colleagues tell me that this technique worked for them and saved them from repeating an embarassing classroom event.

Description: 
Most of us have probably been there. Discussing homonuclear diatomic MO diagrams and on the first day you want to put up the sigma bonding molecular orbital for H2. If you teach it like me, you emphasize the LCAO-MO approach, so you draw a hydrogen atom with its 1s orbital interacting with a hydrogen atom with its 1s orbital...and then you notice giggling from the less mature audience members. My technique will help to prevent this from happening. The technique is in the "faculty only" files section.
Learning Goals: 

The instructor will draw the bonding MO of dihydrogen without accidentally causing laughter in the class or self embarassment.

Corequisites: 
Equipment needs: 

chalkboard or whiteboard

ability to adjust quickly just in case

Prerequisites: 
Implementation Notes: 

I have come close to accidentally drawing the incorrect version of this diagram and I am able to stop myself quickly as illustrated in the instructions. 

Time Required: 
a minute to learn, a lifetime to master.

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