Deeper Analysis of the EAS Nitration of Bromobenzene: A Computational and Spectroscopic Study for the Undergraduate Organic Laboratory

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 21 (2016) pp 166-172

Deeper Analysis of the EAS Nitration of Bromobenzene: A Computational and Spectroscopic Study for the Undergraduate Organic Laboratory

Brian J. Esselman*^,†, Nicholas J. Hill*^,†, William B. Tucker^†,‡, Maria A. Zdanovskaia^† and Asif D. Habib^§

^†Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706 USA. besselman@chem.wisc.edu, hill@chem.wisc.edu; ^‡Current Address: Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215 USA; ^§Department of Chemistry, University of Wisconsin–Waukesha County, 1500 N. University Drive, Waukesha, WI 53188 USA
Received June 10, 2016. Accepted July 17, 2017.

Published: 17 August 2016

Abstract. Electrophilic aromatic substitution (EAS) reactions are ubiquitous in the undergraduate organic chemistry curriculum. Operationally simple EAS nitration reactions are often used in the instructional laboratory as examples of kinetically-controlled processes to predict the regiochemical outcome of the reaction via the Hammond-Leffler postulate. Herein, we present a detailed spectroscopic and computational investigation of the EAS nitration of bromobenzene in which students explore the potential energy surface via modeling of the arenium cation intermediates and determine the regiochemical outcome of the reaction by ¹H-NMR and GC-MS analysis. Spectroscopic examination of the composition of the crude reaction mixture with the support of empirical ¹H-NMR chemical shift parameters and computational data enables students to fully explore the product distribution of this EAS reaction.

Key Words: Laboratories and Demonstrations; organic chemistry; EAS reactions; mechanisms; computational chemistry; spectroscopy; active learning

(*) Corresponding author. (E-mail: hill@chem.wisc.edu)

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Supporting Materials:

The supporting materials include examples of student ¹H-NMR spectra, an “Introduction to NO₂⁺ generation” molecular modeling lecture slide, the introductory spectroscopy exercise and solutions, student laboratory manual chapter and instructor notes, sample student ¹H-NMR spectra, examples of final exam questions, descriptions of varying reaction conditions, and GC column conditions. Solutions to all laboratory or exam questions are available upon request. Additionally, full spectral characterization of each regioisomeric product is provided. (3.5 MB)