Greening Wittig Reactions: Solvent-Free Synthesis of Ethyl trans-Cinnamate and trans-3-(9-Anthryl)-2-Propenoic Acid Ethyl Ester

Author Contact: hweizman@ucsd.edu

Summary

While the Wittig reaction is often used as an example of a reaction with poor atom economy, it is still important to recognize that any reaction, the Wittig included, can be made greener. This solvent-less Witting not only eliminates the hazards associated with tradition solvents, but also uses reagents with little or no known toxicity. This is particularly notable given the relatively high typical yield of 80-85%.

However, the significant greening of the reaction is not the only attractive feature of this experiment. The spectra of the products allows for a very thorough and important discussion of proton NMR. Here educators have an opportunity to teach students how to use coupling constants to determine alkene stereochemistry and how the shape of a molecule can affect the conjugation of the system and how this change in shape can be detected by NMR.

A list of chemicals and equipment, student handout, laboratory procedure, notes for the instructor, NMR spectra, and computational data are all available in the supplemental information.

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

Category Descriptors

Chemistry Concepts

• Aldehydes/Ketones
• Alkenes
• Carbonyl Chemistry
• Esters
• Stereochemistry

Laboratory Techniques

• Extraction
• NMR Spectroscopy
• Recrystallization
• Rotary Evaporation
• Vacuum Filtration

Green Chemistry Principles

• Minimize the Potential for Accidents
• Prevent Waste
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Organic Chemistry

Target Audience

• Colleges/Universities

Source

• Journal Articles