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How the Substituent Effect Influences π-Electron Delocalisation in the Ring of Reactants in the Reaction Defining the Hammett Substituent Constants σm and σp
Int. J. Mol. Sci. 2005, 6(1), 52-62; doi:10.3390/i6010052
Article

13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines

1, 1,* , 2 and 1
1 Department of Chemistry, Technical & Agricultural University, Seminaryjna 3, PL-85-326 Bydgoszcz, Poland 2 Department of Chemistry, P.O. Box 35, FIN-40014, University of Jyväskylä, Finland
* Author to whom correspondence should be addressed.
Received: 16 April 2004 / Revised: 24 January 2005 / Accepted: 25 January 2005 / Published: 31 January 2005
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Abstract

Chemical shifts of the para carbon atoms, δ(13C-4), in a series of aromatic amines were used to calculate the σp, σR and σOR substituent constants for different amino groups. 1-Pyrrolidino, N,N-di-n-butylamino and N,N-diethylamino groups were found to be the most strong electron-donors. ortho-Substitution decreases the donor properties of the amino group. The amino groups in 2,6-di-i-propylaniline and N,N-2,6-tetramethylaniline have very weak electron-donor properties. The nitrogen atom in benzoquinuclidine and N,N-dimethyl-2,6-di-i-propylaniline have an electron-acceptor character. The calculated substituent constants of the amino groups studied are consistent with the spectral and reactivity data available in literature. Values of δ(15N) cannot be used as a direct measure of electronic effects of the N atom in anilines.
Keywords: Amino groups; substituent effects; steric inhibition to resonance; 13C- and 15N-NMR; aromatic amines Amino groups; substituent effects; steric inhibition to resonance; 13C- and 15N-NMR; aromatic amines
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Zakrzewska, A.; Gawinecki, R.; Kolehmainen, E.; Ośmiałowski, B. 13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines. Int. J. Mol. Sci. 2005, 6, 52-62.

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