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Synthesis and NMR Spectral Analysis of Amine Heterocycles: The Effect of Asymmetry on the 1H and 13C NMR Spectra of N,O-Acetals

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Shahrokh Saba , James A. Ciaccio , Jennifer Espinal and Courtney E. Aman

Department of Chemistry, Fordham University, Bronx, NY 10458

J. Chem. Educ., 2007, 84 (6), p 1011

DOI: 10.1021/ed084p1011

Publication Date (Web): June 1, 2007

Section:

History, Education, and Documentation

Abstract

We describe an undergraduate organic laboratory experiment in which students prepare two structurally similar heterocyclic amines: one achiral, 3-isopropyloxazolidine, 2, and the other chiral, (±)-3-isopropyl-2-(4-nitrophenyl)oxazolidine, 3. These N,O-acetals differ only by the presence of a single ring substituent that introduces asymmetry; thus, each compound has distinct 1H and 13C NMR spectral patterns. Each student prepares 2-(isopropylamino)ethanol, 1, and then the class is divided into two groups: one group prepares 2, and the other group prepares 3. NMR spectroscopy clearly indicates that the nuclei of the methyl groups (and the hydrogens of each methylene) of 2 and 3 are enantiotopic and diastereotopic, respectively. Students must explain why the NMR spectra of 3 have more peaks in the aliphatic region and increased coupling in the 1H spectrum, leading to a discussion of prochirality and topicity of ligands within a single molecule. This operationally straightforward experiment is a meaningful exercise in chemical synthesis and spectral problem solving, and students sample the benefits of collaborative work by dividing up the synthetic and analytical tasks and then sharing their data.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Laboratory Instruction

Keywords (Pedagogy):

Collaborative / Cooperative Learning

Keywords (Subject):

Amines / Ammonium Compounds

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Using NMR To Probe the Regio- and Stereochemistry of the Hydration of 1-Hexene
Shahrokh Saba, Donald D. Clarke, Christa Iwanoski, and Thomas Lobasso
Journal of Chemical Education2010 87 (11), 1238-1241
- Using NMR To Probe the Regio- and Stereochemistry of the Hydration of 1-Hexene
  Shahrokh Saba, Donald D. Clarke, Christa Iwanoski, and Thomas Lobasso
  Journal of Chemical Education2010 87 (11), 1238-1241
  This undergraduate organic laboratory experiment complements previously described and popular experiments on hydration of 1-hexene where students experimentally establish the Markovnikov regioselectivity of alkene hydration. In this experiment, students ...
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