Contact Information

  • David M. Collard
  • Assoc. Professor and Director of Graduate Studies
  • School of Chemistry and Biochemistry
  • Georgia Institute of Technology
  • Atlanta, GA 30332-0400
(404) 894 - 4026

Synthesis and Spectroscopic Analysis of a Cyclic Acetal: a Dehydration Performed in Aqueous Solution

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An organic chemistry laboratory experiment involving an equilibrium dehydration reaction where two hydroxyl groups of a tetra-alcohol, pentaerythritol, react with benzaldehyde in aqueous acid to form a benzal, 5,5-bis(hydroxymethyl)-2-phenyl-1,3-dioxane (an acetal derived from benzaldehyde) is described. This reaction can be used to illustrate the mechanism for the formation of ketals (and acetals) and their use as protecting groups for ketones (and aldehydes). Since the product contains nonequivalent geminal protons this experiment is appropriate for the analysis of inequivalent protons by NMR spectroscopy. The temperature sensitivity of this reaction also enables this experiment to be used as a group exercise to illustrate optimization of reaction conditions to maximize product yield. The green components of this procedure illustrate the use of inexpensive, nontoxic starting materials and water as a solvent.

Supplemental materials are provided on the J. Chem. Educ. website and include laboratory procedures, sample questions and instructor notes.

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


Collard, D. M.; Jones, A. G.; Kriegel, R. M. J. Chem. Educ., Print 2001, 78, pp 70-72.

J. Chem. Educ. (Abstract only)

Category Descriptors

Chemistry Concepts
  • Aldehydes/Ketones
  • Aqueous Solution Chemistry
  • Equilibrium
Laboratory Techniques
  • Assembly of Reaction Apparatus
  • Microscale Lab
  • NMR Spectroscopy
Green Chemistry Principles
  • Design Less Hazardous Chemical Syntheses
  • Use Safer Solvents/Reaction Conditions
Chemistry Subdiscipline
  • Organic Chemistry
Target Audience
  • Colleges/Universities
  • Journal Articles