Intermolecular interactions

29 Jul 2019

Introduction to Drago's ECW Acid-Base Model

Submitted by Colleen Partigianoni, Ferris State University
Description: 

This LO was created to introduce Drago’s ECW model, which is an important contribution to the discussion of Lewis acid-base interactions. Unlike the qualitative Pearson’s HSAB model (Hard Soft Acid-Base model,) the quantitative ECW model can be used to correlate and predict the enthalpies of adduct formation and to obtain enthalpy changes for displacement or exchange reactions involving many Lewis acids and bases.  Unlike all other acid-base models, graphical displays of the ECW model clearly show that there is no one order of acid or base strengths, and illustrate that two parameters are needed for each acid and base to provide an order of acid or base strength.  The ECW model can also provide a measure of steric strain energy or pi bonding stabilization energy accompanying adduct formation, which is not possible with any other acid-base model. 

This set of slides is intended to provide a basic introduction to the model and several examples of predicting energy changes using the model. It also illustrates how to construct and interpret a graphical display of the model.

 It should be noted that this LO is not in the PowerPoint format, but instead is a more extensive set of notes for instructors who are not familiar with the ECW model. It could be condensed and rewritten in the more standard PowerPoint format.

There is also an ECW problem set LO that can used to supplement this LO.

Prerequisites: 
Corequisites: 
Learning Goals: 

After viewing the slides, students, when provided with appropriate data, should be able to:

  • Calculate sigma bond strength in Lewis acid-base adducts using Drago’s ECW model.
  • Show how to deal with any constant energy contribution (W) to the reaction of a particular acid (or base) that is independent of the base (or acid) when an adduct is formed.
  • Garner information regarding steric effects and pi bond stabilization energy in Lewis acid-base adducts using the ECW model.
  • Show using a graphic display of ECW that two parameters for each acid and each base are needed in acid-base models to determine relative strengths of donors and acceptors.
Evaluation
Evaluation Methods: 

This LO has not been used yet and evaluation information will be posted at a later date.

8 Jun 2019

VIPEr Fellows 2019 Workshop Favorites

Submitted by Barbara Reisner, James Madison University

During our first fellows workshop, the first cohort of VIPEr fellows pulled together learning objects that they've used and liked or want to try the next time they teach their inorganic courses.

7 Apr 2019

Encapsulation of Small Molecule Guests by a Self-Assembling Superstructure

Submitted by Shirley Lin, United States Naval Academy
Evaluation Methods: 

I have not yet implemented this LO. As with other literature discussions, instructors could collect the completed worksheets (by an individual student or in groups of students) for evaluation.

Evaluation Results: 

I have not yet implemented this LO so there are currently no evaluation results to share.

Description: 

This literature discussion focuses upon two journal articles by the Rebek group on the synthesis and host-guest chemistry observed with the "tennis ball." 

Corequisites: 
Learning Goals: 

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

  • provide examples of supramolecular systems in nature that use reversible, weak noncovalent interactions 
  • define terms in supramolecular chemistry such as host, guest, and self-complementary
  • identify the number and location of hydrogen bonds within the "tennis ball" assembly
  • draw common organic reaction mechanisms for the synthesis of the "tennis ball" subunits
  • describe the physical and spectroscopic/spectrometric techniques used to provide evidence for assembly of a host-guest system
  • explain the observed thermodynamic parameters that are important for encapsulation of small molecule guests by the "tennis ball"
Implementation Notes: 

This LO could be used at the end of a traditional 2-semester organic chemistry sequence as an introduction to organic supramolecular systems, as an organic chemistry example within a discussion about inorganic supramolecular chemistry, or in an upper-division elective course about supramolecular chemistry. The LO topic, the "tennis ball," has a published laboratory experiment in J. Chem. Educ. (found here). Time permitting, instructors could have students read the article and complete the literature discussion before executing the experiment in the lab.

As usual, instructors may wish to mix-and-match questions to suit their learning goals.

Time Required: 
depends upon implementation; minimum of 20-30 minutes for the literature discussion if students read an d answer questions outside of class
3 Mar 2019

Supramolecular Chemistry Videos

Submitted by Shirley Lin, United States Naval Academy
Evaluation Methods: 

I have yet to use this resource with students and therefore have no assessment of student learning to share at this time.

Evaluation Results: 

I have yet to use this resource with students.

Description: 

The Rebek Laboratory homepage contains information on and molecular visualizations of a variety of host-guest systems developed by the research group over several decades. The theme behind this set of examples is the use of hydrogen-bonding to achieve self-assembly. Under the "Research" tab, one can find four videos with narration: an introduction to molecular assembly and three videos of specific examples of self-assembled host systems (the cavitand, the cylinder and the volleyball). In addition, at the bottom of the tab, there are links to JSmol files for 5 host systems (tennis ball, jelly donut, cylindrical capsule, softball, and tetrameric capsule) that allow the assemblies to be visualized interactively.

 

This is a great resource for faculty looking for ways to incorporate the new ACS Committee on Professional Training guidelines to discuss macromolecular, supramolecular, mesoscale and nanoscale systems within the framework of their existing curricula.

Corequisites: 
Learning Goals: 

I have not yet used this resource with students but here are some possible relevant learning goals.

After viewing the Rebek Laboratory Homepage web source, students will be able to:

1) classify various self-assembled host-guest systems by the number of molecular components forming the assembly

2) identify the number and position of the hydrogen bonds that are responsible for the assembly of each host

3) identify the functional groups on the components of the host systems that are responsible for hydrogen bonding

4) state the experimentally determined percent volume of space generally occupied by guests that are encapsulated in these host systems

 

Subdiscipline: 
Implementation Notes: 

I have yet to use this website in my teaching but I hope that it may be a resource in expanding our curriculum in supramolecular chemistry.

Time Required: 
depends on use

Pages

Subscribe to RSS - Intermolecular interactions