Contact Information

Author
  • James E. Hutchison
  • Professor
  • Chemistry
  • Univ. of Oregon
  • Eugene, OR 97403
Email
Phone
(541) 346 - 4228
Website

Microwave Synthesis of Tetraphenylporphyrin

Laboratory Procedures (PDF)

Author Contact: hutch@uoregon.edu

Summary

In the present experiment students prepare a porphyrin, tetraphenylporphyrin, from four molecules each of pyrrole and benzaldehyde. The carbon framework of the porphyrin is assembled through eight electrophilic substitutions between benzaldehyde and pyrrole to produce a porphyrinogen. Oxidation of the porphyrinogen during the reaction yields the porphyrin (an 18-electron aromatic compound).

Traditionally, porphyrin syntheses have been carried out in corrosive, high-boiling solvents, such as propionic acid or have been done in large volumes of a halogenated solvent containing a corrosive Lewis acid catalyst. In many cases, toxic oxidizing compounds are used to convert the porphyrinogen to porphyrin. In this experiment, students employ a method of porphyrin synthesis that is solventless-it is carried out on a solid support. The two reagents, pyrrole and benzaldehyde, react on the support under irradiation in a conventional microwave oven. The product is eluted off the solid support with a small amount of solvent. Usually one purifies porphyrins by column chromatography often employing chlorinated solvents such as methylene chloride or chloroform. In this experiment, a safer chromatography solvent mixture (hexanes and ethyl acetate) is used. The link to the laboratory procedures includes pre- and -post lab questions.

Summary prepared May 2005 by Julie A. Haack, Department of Chemistry at the University of Oregon.

Source

Warner, M.; Succaw, G.; Doxsee, K. M.; Hutchison, J. E. Microwave Synthesis of Tetraphenylporphyrin Greener Approaches to Undergraduate Chemistry Experiments, Print Kirchhoff, M., Ryan, M., Eds.; American Chemical Society: Washington D.C., 2002; pp 27-31.

Category Descriptors

Chemistry Concepts
  • Electrophilic Substitution
  • Oxidation/Reduction Chemistry
  • Solid-Support Reagents
Laboratory Techniques
  • Assembly of Reaction Apparatus
  • Liquid Chromatography
  • Metallation
  • Thin-layer Chromatography
  • UV-Vis Spectroscopy
Green Chemistry Principles
  • Avoid Chemical Derivatives
  • Increase Energy Efficiency
  • Maximize Atom Economy
  • Prevent Waste
  • Use Safer Solvents/Reaction Conditions
Chemistry Subdiscipline
  • Organic Chemistry
Target Audience
  • Colleges/Universities
Source
  • Books