title: Monitoring chemical reactions by low-field benchtop NMR at 45 MHz: pros and cons.
abstract: Monitoring chemical reactions is the key to controlling chemical processes where NMR can provide support. High-field NMR gives detailed structural information on chemical compounds and reactions; however, it is expensive and complex to operate. Conversely, low-field NMR instruments are simple and relatively inexpensive alternatives. While low-field NMR does not provide the detailed information as the high-field instruments as a result of their smaller chemical shift dispersion and the complex secondary coupling, it remains of practical value as a process analytical technology (PAT) tool and is complimentary to other established methods, such as ReactIR and Raman spectroscopy. We have tested a picoSpin-45 (currently under ThermoFisher Scientific) benchtop NMR instrument to monitor three types of reactions by 1D (1) H NMR: a Fischer esterification, a Suzuki cross-coupling, and the formation of an oxime. The Fischer esterification is a relatively simple reaction run at high concentration and served as proof of concept. The Suzuki coupling is an example of a more complex, commonly used reaction involving overlapping signals. Finally, the oxime formation involved a reaction in two phases that cannot be monitored by other PAT tools. Here, we discuss the pros and cons of monitoring these reactions at a low-field of 45 MHz by 1D (1) H NMR. Copyright © 2015 John Wiley & Sons, Ltd.
authors.affiliation: Department of Attribute Sciences, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA, 91320-1799, USA.
authors.forename: Maria Victoria
authors.identifier: http://orcid.org/0000-0002-8429-9534
authors.initials: MV
authors.lastname: Silva Elipe
authors.affiliation: Department of Attribute Sciences, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA, 91320-1799, USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Milburn
keywords: 1D 1H NMR; 45 MHz; Fischer esterification; NMR; Suzuki coupling; low-field NMR; reaction monitoring; tubeless NMR; two-phase reaction