Applying the (n + 1) Rule Using the Alcohol Peak in a 45 MHz NMR Spectrometer

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 20 (2015) pp 79-82

Applying the (n + 1) Rule Using the Alcohol Peak in a 45 MHz NMR Spectrometer

Meden F. Isaac-Lam

Department of Biology and Chemistry, Purdue University North Central, Westville, IN 46391, isaaclam@pnc.edu
Received January 12, 2015. Accepted March 18, 2015.

Published: 20 April 2015

Abstract. Nuclear magnetic resonance (NMR) is an indispensable spectroscopic method to determine structures of organic molecules. A 45 MHz NMR spectrometer was used to acquire spectra of several unknown liquids (alcohols, esters and ketones) run as neat samples. For the unknown alcohols, splitting of the OH peak which followed the (n + 1) rule was observed, and must be explained to students to avoid incorrect structural assignment. The OH peak in a primary, secondary and tertiary alcohol appeared as a triplet, doublet, and singlet, respectively. This experiment was introduced in the second-semester organic chemistry laboratory course as an exercise involving structural elucidation of unknown liquid using NMR and IR spectroscopic methods.

Key Words: Laboratories and Demonstrations; organic chemistry; NMR

(*) Corresponding author. (E-mail: isaaclam@pnc.edu )

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Supporting Materials:

Handout and instructions for students containing procedures for the experiment. (558 KB)