Reduction of 4-tert-Butylcyclohexanone: a Laboratory Class Project in Diastereoselectivity and Thermodynamic vs. Kinetic Control

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 14 Issue 6 (2009) pp 232-235

Reduction of 4-tert-Butylcyclohexanone: a Laboratory Class Project in Diastereoselectivity and Thermodynamic vs. Kinetic Control

Michael Novak*, Benjamin W. Gung, James W. Hershberger, Richard T. Taylor, Bright Emenike, Mrinal Chakraborty, Ashley N. Scioneaux, Amanda E. Ponsot, and Philias Daka

Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, email: novakm@muohio.edu
Received December 8, 2008. Accepted September 2, 2009

Published online: 29 December 2009

Abstract. In the first semester majors’ organic laboratory course at Miami, students work on a class project in which individual students contribute data to establish the diastereoselectivity of three different methods of reduction of 4-tert-butylcyclohexanone: NaBH₄/EtOH, lithium tri-sec-butylborohydride (L-Selectride)/THF, and Al(isoPrO)₃/isoPrOH (Meerwein-Pondorff-Verley or MPV reduction). ¹H NMR analysis of the crude product mixtures provides a convenient method to establish the cis/trans isomer ratio of the product 4-tert-butylcyclohexanols. Reduction with NaBH₄ leads predominately to the trans-isomer ((88 ± 3)% trans), L-Selectride yields predominately the cis-isomer ((92 ± 1)% cis), while MPV reduction leads to an equilibrium mixture containing (23 ± 4)% cis-isomer. After individual students report their stereoselectivity results on one of the three methods, the instructor compiles and averages the data, and reports it back to the students. The students write a formal report on the project in which the issues of diastereoselectivity and thermodynamic vs. kinetic control of a product mixture are addressed.

Key Words: Laboratories and Demonstrations; organic chemistry

(*) Corresponding author. (E-mail: novakm@muohio.edu)

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Supporting Materials:

Laboratory handout for this experiment and guidelines for formal laboratory write-up (78 KB).