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A Simple and Convenient Method for Generation and NMR Observation of Stable Carbanions: An Advanced Undergraduate Laboratory Experiment

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Hamid S. Kasmai

Department of Chemistry, East Tennessee State University, Johnson City, TN 37614

J. Chem. Educ., 1999, 76 (6), p 830

DOI: 10.1021/ed076p830

Publication Date (Web): June 1, 1999

Abstract

A simple and convenient method for the generation and NMR study of stable carbanions is described. Cyclopentadienide, indenide, fluorenide, xanthenide-d1, thioxanthenide-d1, 9,10-dihydroanthracenide-d3, and imidazolide anions were prepared from their corresponding conjugate acid progenitors in K⁺DMSYL-d6^–/DMSO-d6 base/solvent system and their ¹H and ¹³C NMR spectra were recorded. The data and sample spectra illustrate that reliable and good quality NMR spectra of stable carbanions may be obtained using simple laboratory setups and NMR instruments operating at 90 MHz or lower frequencies. The experiments described provide a good opportunity for students to apply the basic principles of ¹H and ¹³C NMR spectrometry and the interesting topic of the exchange phenomenon in NMR. In addition, a study of acidities of carbon acids, calculations of electron and charge densities of carbanions, and the study of the correlation between the calculated charge densities and recorded NMR chemical shifts may be integrated into these activities.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Organic Chemistry

Keywords (Feature):

Advanced Chemistry Classroom and Laboratory

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Acids / Bases

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This article has been cited by 5 ACS Journal articles (5 most recent appear below).

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An Acid Hydrocarbon: A Chemical Paradox
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Journal of Chemical Education2004 81 (1), 65
- An Acid Hydrocarbon: A Chemical Paradox
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Synthesis, Kinetics, and Thermodynamics: An Advanced Laboratory Investigation of the Cis-Trans Isomerization of Mo(CO)4(PR3)2
Kim E. Mooney , Ashfaq A. Bengali
Journal of Chemical Education2003 80 (9), 1044
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Determination of the Regiochemistry of Disubstituted Arenes Generated by Addition of a Carbanion to the (η6-Anisole)Cr(CO)3 Complex
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Journal of Chemical Education2001 78 (1), 68
- Determination of the Regiochemistry of Disubstituted Arenes Generated by Addition of a Carbanion to the (η6-Anisole)Cr(CO)3 Complex
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  It has become increasingly important to demonstrate to undergraduates that chemistry is not many separate subfields, but rather a set of interconnected concepts. We describe a laboratory activity that integrates fundamental concepts of organic and ...
  Abstract | Hi-Res PDF | PDF w/ Links