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

International Journal of Molecular Sciences

Anna Zakrzewska²  Ryszard Gawinecki²  Erkki Kolehmainen¹ 

[1] Department of Chemistry, P.O. Box 35, FIN-40014, University of Jyväskylä, Finland;Department of Chemistry, Technical & Agricultural University, Seminaryjna 3, PL-85-326 Bydgoszcz, Poland

关键词: Amino groups;    substituent effects;    steric inhibition to resonance;    ¹³C- and ¹⁵N-NMR;    aromatic amines;   

DOI  :  10.3390/i6010052

来源: mdpi

【 摘 要 】

Chemical shifts of the para carbon atoms, δ(¹³C-4), in a series of aromatic amines were used to calculate the σ_p, σ_R andsubstituent 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.

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