Implementation of picoSpin Benchtop NMR Instruments into Organic Chemistry Teaching Laboratories through Spectral Analysis of Fischer Esterification Products

Abstract

1H NMR analysis is an important analytical technique presented in introductory organic chemistry courses. NMR instrument access is limited for undergraduate organic chemistry students due to the size of the instrument, price of NMR solvents, and the maintenance level required for instrument upkeep. The University of Georgia Chemistry Department recently acquired three picoSpin desktop 1H NMR instruments for the undergraduate organic laboratories. These instruments can sit on a standard lab bench, can analyze samples without NMR solvents, and are easily maintained. In this Fischer esterification experiment, students used unknown starting alcohols to synthesize esters through Fischer esterification. Upon completion of the reaction, students identified the unknown starting alcohol via spectral analyses of the products. Over the course of 4 semesters, 704 out of 940 students (75%) correctly identified the starting alcohol and 71% of students surveyed indicated that 1H NMR spectrum was the most helpful identification tool in their analyses. This experiment established for students the utility of NMR spectral analysis and provided them with the opportunity to employ technology commonly used in academic research facilities.

Applications of benchtop NMR in the organic chemistry instructional laboratory

“…For example, we modified the Fischer esterification reaction to include several unknown alcohols. 9,10 Students perform a standard acid-catalyzed esterification using the same carboxylic acid but with individually assigned unknown alcohols. The structures for the product esters are elucidated by 1 H NMR analysis using the benchtop NMR spectrometer.…”

“…At the University of Georgia, we have developed and implemented a library of experiments with unknown substrates or reagent sets, called multi‐outcome experiments (MOEs). For example, we modified the Fischer esterification reaction to include several unknown alcohols 9,10 . Students perform a standard acid‐catalyzed esterification using the same carboxylic acid but with individually assigned unknown alcohols.…”

Benchtop NMR Spectroscopy and Spectral Analysis of the cis- and trans-Stilbene Products of the Wittig Reaction

“…Several universities have had success using benchtop NMR spectrometers at an operating frequency of 45 MHz, and these low-field systems have been used to analyse Fischer esterification products, 13 and the free radical-mediated bromination of ethylbenzene 14 . Moreover, the portability 90 of these systems also permits them to be used in university-high school partnership program in the USA 15 , and university outreach strategies in the UK.…”

A Visual Organic Chemistry Reaction: The Synthesis of 4-Amino-3-nitrobenzoic Acid Methyl Ester via Fischer Esterification

“…2 However, more commonly, we see that aspirin synthesis is now often performed in secondary education at high school, and thus there is a drop in the students' engagement if repeated at a tertiary level. 3 Fischer esterification is an important topic included in most introductory chemistry courses, and examples of these reactions are abundant 4,5 . The reaction is a reversible condensation reaction where a carboxylic acid reacts with an alcohol to produce an ester and water.…”