A Green, Guided-Inquiry Based Electrophilic Aromatic Substitution for the Organic Chemistry Laboratory

Author Contact: stdeal@georgiasouthern.edu

Summary

This exercise demonstrates the regioselectivity of substituted aromatic systems while reducing the amount and hazards of the waste produced by the class. Although typical iodinations involve either absurd amounts of derivitization (i.e., nitration, then reduction to aniline, formation of diazonium, then iodinization) or use of hazardous/expensive reagents (iodine and mercury acetate, bis(pyridine)iodonium tetrafluoroborate), this experiment teaches important aromatic chemistry using safe and inexpensive reagents.

Students are first asked to predict where the iodine will substitute on salicylamide. Then, by simply adding household bleach and sodium iodide, they perform the iodination and analyze their product by IR spectroscopy. An interesting aspect of this lab is the analysis of the substitution pattern on their product by IR spectroscopy as opposed to proton NMR.

Supplemental information includes background information regarding electrophilic aromatic substitutions and using IR to determine substitution patterns, experimental procedure, student questions and key, a list of necessary materials, and instructor notes.

Summary prepared December 2008 by Douglas M. Young at the University of Oregon.

Category Descriptors

Chemistry Concepts

• Aromatic Compounds
• Electrophilic Substitution

Laboratory Techniques

• IR Spectroscopy
• pH
• Recrystallization
• Vacuum Filtration

Green Chemistry Principles

• Avoid Chemical Derivatives
• Maximize Atom Economy
• Prevent Waste

Chemistry Subdiscipline

• Organic Chemistry

Target Audience

• Colleges/Universities

Source

• Journal Articles