Electrophilic Aromatic Substitution
At a Glance
Discipline
- STEM
- Chemistry
Instructional Level
- College & CEGEP
- University
Course
- Organic Chemistry
Tasks in Workflow
Social Plane(s)
- Individual
- Group
- Whole Class
Type of Tasks
- Discussing
- Analyzing
- Reviewing & assessing peers
- Revising & improving
- Writing
Technical Details
Useful Technologies
- Interactive whiteboards
Time
- Single class period (< 90 mins)
Instructional Purpose
- Application & knowledge building
- Assessment & knowledge refinement
Overview
In groups, students analyze and sort 5 substituents based on whether they are activating or deactivating groups at a whiteboard or interactive board. Groups switch boards to peer review and annotate another group’s work before returning to their original board to discuss the comments made by their peers.
Each group then selects one activating and one deactivating substituent from their sorted compounds to add to the benzene ring. They draw resonance structures for both. This is followed by another period of peer review and annotation by another group.
The instructor then assigns each group a distinct reagent to carry out electrophilic aromatic substitution onto benzene rings attached to each substituent students previously sorted. Groups complete these five reactions, then once again switch whiteboards to peer review and annotate another groups work.
Groups then circulate around the room (gallery walk) to examine and discuss all finalized reactions posted by their peers. Each group compiles a flow chart outlining the steps required to solve a electrophilic aromatic substitution problem. Individual students then, out of class, apply their flow chart in solving related questions, modifying it until it is robust and using it as a study aid for future examinations.
Instructional Objectives
Students will learn to identify and sort activating and deactivating substituents in electrophilic aromatic substitution, draw resonance structures for benzene, and examine substituent effects in electrophilic aromatic substitution.
Workflow & Materials
Activity Workflow
Contributor's Notes
Benefits
Challenges
Tips
Benefits
Students can review the work done by their peers, revisiting the content. They assess their own understanding by providing explanations for their work.
Challenges
If students don’t do the prior reading, it is difficult for them to participate in the activity. Consequently, incorporating a mini lecture or summary at the start of the activity can place students on a more even playing field.
Some groups are much faster than others. Additional steps or problems can be provided for students who have additional time.
Tips
If time is too short for a gallery walk, the instructor may compile the reactions completed by all groups, check them for errors, then distribute them, allowing students to construct the flow chart outside of class time. Another option is to have each group (or the instructor) post the reactions into an online collaborative platform.
When drawing out resonance structure, it is essential students realize that there is a loss of aromaticity. They must also realize the effect the substituent will have on subsequent substitution.
Including “exceptions” in the problems helps generate more discussions within each group. Students need to gain a better understanding of why the “exception” is truly an exception, and prevents students from blindly applying the same recipe to all problems.
Applied Strategies
Published: 18/09/2018
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