NMR Kinetics of the SN2 Reaction between BuBr and I–: An Introductory Organic Chemistry Laboratory Exercise

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 concentration-dependence of both the organic substrate and the nucleophile under pseudo-first-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.