Unexpected Synthetic Outcomes from a Traditional Separations Laboratory: A Learning Experience for Faculty and Students

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 25 (2020) pp 105-108

Unexpected Synthetic Outcomes from a Traditional Separations Laboratory: A Learning Experience for Faculty and Students

Sylvia S. Bridges^†, Kevin M. Bucholtz^†, David R. Goode^†, Margaret K. Meadows^†, Ryan McGuire^†, Katherine M. Masters^‡, Adam M. Kiefer*^,†

^†Department of Chemistry, Mercer University, Macon, GA 31207, Kiefer_am@mercer.edu;^‡‡Department of Chemistry, Pennsylvania State University, University Park, PA 16802
Received January 24, 2020. Accepted May 2, 2020.

Published: 6 May 2020

Abstract. The introduction of ¹H NMR analysis into a trusted separation experiment in an undergraduate Organic Chemistry laboratory has yielded a revelatory unexpected outcome. When students extract acetylsalicylic acid (aspirin) from dichloromethane using a sodium hydroxide solution followed by precipitation with acid, the separated sample collected is not aspirin but instead the saponified salicylic acid product. Faculty investigated the experiment to determine the conditions under which the hydrolysis reaction occurred. In response to the failed separation experiment, students were guided through a discussion of carbonyl reactivity along with an experiment in which they converted the collected salicylic acid into acetylsalicylic acid. Faculty investigated modifications to the separation experiment that prevent the unwanted hydrolysis reaction in future iterations. The experience underscores the importance of product characterization along with adequate testing of published laboratory experiments for both faculty and undergraduate students.

Key Words: Laboratories and Demonstrations; organic chemistry; second-year undergraduate; laboratory instruction; separation science; NMR spectroscopy; misconceptions/discrepant events; esters

(*) Corresponding author. (E-mail: Kiefer_am@mercer.edu )

Article in PDF format (221 KB) HTML format

Supporting Materials:

The Supporting Information are available online include the Student Procedures from 2018, 2015, 2005, and relevant student ¹H NMR spectra (PDF). (2200 KB)