Sodium Borohydride Reduction of Vanillin: A Low Solvent Synthesis of Vanillyl Alcohol

Laboratory Procedure

Author Contact: clecher@marian.edu

Summary

This pleasant-smelling reaction is a greener version of the classical borohydride reduction. The experiment utilizes a novel scenario to introduce reduction chemistry and to highlight the importance of experimental design. The vanillin is dissolved in a minimal amount of ethanol, reduced with sodium borohydride, and upon acidification, vanillyl alcohol precipitates from the resulting aqueous reaction mixture. This eliminates the need for an organic extraction, which is typically performed with this type of reaction. Students typically achieve excellent yields, with typical yield ranging from 65 to 95%. The exercise provides a good context for discussing pKas as the acidic phenol is deprotonated by the borohydride, generating hydrogen gas.

Summary prepared March 2007 by Carl S. Lecher, Department of Chemistry, Marian College.

Category Descriptors

Chemistry Concepts

• Carbonyl Chemistry
• Natural Products
• Oxidation/Reduction Chemistry
• Preparation of Alcohols
• Solutions/Solvents

Laboratory Techniques

• IR Spectroscopy
• Melting Points and Melting Ranges
• pH
• Recrystallization
• Vacuum Filtration

Green Chemistry Principles

• Prevent Waste
• Use Renewable Feedstocks
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Organic Chemistry

Target Audience

• Colleges/Universities

Source

• Original Contributions - unpublished