Effect of substituents on the nickel-induced contact shifts in aromatic amines. Comparison with spin delocalization in phenyl, benzyl, and related radicals was written by Underwood, Graham R.;Clyde, William C.;Zitter, Mark S.. And the article was included in Journal of Physical Chemistry in 1981.Reference of 644-98-4 This article mentions the following:
Ni[CH(COMe)2]2 (I)-induced proton and 13C NMR contact shifts were studied in a series of anilines, pyridines and heterocycles. Substituents have little effect on the shifts unless bonded directly to N or separated from it by just 1 atom. INDO calculations on 2-substituted Ph radicals suggest that the singly occupied orbital is bent slightly away from the substituent; the ESR hyperfine splitting constants as well as the Ni-induced shifts reflect this distortion. The specificity of I for the N lone pair, the relative constancy of its induced shifts, and their ready interpretation make this a useful NMR shift reagent for amines. In the experiment, the researchers used many compounds, for example, 2-Isopropylpyridine (cas: 644-98-4Reference of 644-98-4).
2-Isopropylpyridine (cas: 644-98-4) belongs to pyridine derivatives. Pyridine’s the lone pair does not contribute to the aromatic system but importantly influences the chemical properties of pyridine, as it easily supports bond formation via an electrophilic attack. One of the examples of pyridines is the well-known alkaloid lithoprimidine, which is an A3 adenosine receptor antagonist and N,N-dimethylaminopyridine (DMAP) analog, commonly used in organic synthesis.Reference of 644-98-4