NMR Kinetics of the SN2 Reaction between BuBr and I−: An
Introductory Organic Chemistry Laboratory Exercise
T. Andrew Mobley*
Department of Chemistry, Grinnell College, Grinnell, Iowa 50112, United States S Supporting Information
ABSTRACT: A simple organic chemistry experiment is described that investigates the kinetics of the reaction between 1-bromobutane (BuBr) and iodide (I−) as followed by observing the disappearance of BuBr and the appearance of 1-iodobutane (BuI) using 1H NMR spectroscopy. In small groups of three to four, students acquire data to examine the concentrationdependence of both the organic substrate and the nucleophile under pseudoﬁrst-order and second-order conditions. After data processing, students analyze three data sets (one second-order experiment, and two ﬁrst-order experiments with diﬀerent concentrations of iodide) using an electronic spreadsheet. Students discuss the experimentally determined rate law, comparing it to that predicted for this SN2 reaction.
KEYWORDS: Second-Year Undergraduate, Hands-On Learning/Manipulatives, Laboratory Instruction, Organic Chemistry, Physical Chemistry, Kinetics, Rate Law, Mechanisms of Reactions, Nucleophilic Substitution, NMR Spectroscopy or the last 10 years, an introduction to kinetics in the ﬁrst term of second-year undergraduate organic chemistry has
been taught with the experiment described herein; approximately 1000 students have completed the experiment.1 The introductory organic chemistry course serves as an ideal setting for teaching kinetic theory, with this experiment coming twothirds of the way through the ﬁrst semester of a two-semester organic sequence. At this point, our students have a ﬁrm basis in structural concepts, are able to translate simple NMR spectra into chemical structures, and understand the concept of a
reaction mechanism. Concurrent with this experiment, students are learning in the classroom the fundamentals...
References: the Organic Laboratory. In Abstracts of Papers, 225th ACS National
Meeting, New Orleans, LA, March 23−27, 2003; American Chemical
Society: Washington, DC, 2003; CHED-1277.
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