Synthesis and Use of Ethyl 6-Acetyloxyhexanoate as an Internal Standard: An Interdisciplinary Experiment for an Undergraduate Chemistry Laboratory

Abstract

The combination of organic synthesis and analytical chemistry into a related laboratory experiment is an excellent demonstration of the utility of making a compound to then be used further. Herein we describe an undergraduate laboratory experiment that involves the straightforward synthesis of an internal standard, ethyl 6-acetyloxyhexanoate, for the quantification of various aroma compounds in juice through GC-FID analysis. In addition to the organic synthetic procedures of undertaking a reaction under reflux, separation, and extraction protocols followed by determining the purity of a synthesized compound, this experiment also facilitates the teaching of making standard solutions, using solid phase extraction, preparing samples, and performing and interpreting the results of GC-FID analysis.

A Problem-Based Approach to Teaching the Internal Standard Method by ATR-FTIR Spectroscopy

“…3,9−15 Recently, published laboratory experiments which contain learning outcomes for teaching the internal standard method include: identifying and qualifying linalool in essential oils using SPME-GC-MS, 11 assessing blood alcohol content within a forensic context 14 and an analysis of ethanol content in beer, 9 both via gas chromatography, as well as quantifying fatty acids in cooking oils using GC-MS, 10 and synthesizing and using ethyl 6-acetyloxyhexanote as an internal standard in the quantification of aroma compounds in juices by GC-FID. 12 While the experiment outlined within this paper presents students with the opportunity to select their internal standard as part of the laboratory exercise, Johnson et al 11 describe an experiment in which their students select their internal standards prior to the experiment within the prelab exercise. This juxtaposition of how students engage in the internal standard selection process shows the different pedagogical approaches that may be taken, providing different benefits depending on the time and resources required within the laboratory.…”

“…Many undergraduate laboratory experiments described in the literature for spectroscopic analysis utilize the internal standard method of calibration and specifically focus on student understanding of the method as a learning goal of the laboratory. ,− Recently, published laboratory experiments which contain learning outcomes for teaching the internal standard method include: identifying and qualifying linalool in essential oils using SPME-GC-MS, assessing blood alcohol content within a forensic context and an analysis of ethanol content in beer, both via gas chromatography, as well as quantifying fatty acids in cooking oils using GC-MS, and synthesizing and using ethyl 6-acetyloxyhexanote as an internal standard in the quantification of aroma compounds in juices by GC-FID . While the experiment outlined within this paper presents students with the opportunity to select their internal standard as part of the laboratory exercise, Johnson et al describe an experiment in which their students select their internal standards prior to the experiment within the prelab exercise.…”

Water Depollution Control: A Gateway to Reaction Monitoring and Analytical Chemistry

“…We adapted the reaction monitoring to the laboratory classroom and optimized the reaction conditions to reach 75% degradation within 2 h: the students were asked to follow the degradation both by UV–vis spectrophotometry and gas chromatography (GC) with an internal standard method . Both of these techniques required the use of specific and accurate equipment such as mechanical pipettes or syringes.…”