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A Proton Dance: Wheland Complexes and Ammonium Salts Obtained from Organic Acids and 1,3,5-Tris(N,N-dialkylamino)benzene Derivatives

[ Vol. 18 , Issue. 4 ]

Author(s):

Carla Boga, Luciano Forlani, Silvia Tozzi, Erminia Del Vecchio, Andrea Mazzanti, Magda Monari and Nicola Zanna   Pages 512 - 523 ( 12 )

Abstract:


The reaction of a series of symmetric and unsymmetric triaminobenzene derivatives with proton as electrophile has been studied. The formation of both Wheland complex (C-H salt) and N-H salt in relative amount depending on the experimental conditions has been observed. In the case of the attack of the proton on the nitrogen atom, the 1H and 13C NMR spectra showed the equivalence of three aromatic protons (and related carbon atoms) of the adduct thus indicating that salification occurs on a non-defined nitrogen atom. This behavior can be explained hypothesizing motion of the proton from a nitrogen atom to another in a motion that could not permit to define the protonation site. On the contrary, X-ray diffraction analysis on crystals of the NH salts reveals that in the solid state the proton is situated in a well-defined position.

Keywords:

Aromatic substitution, nuclear magnetic resonance, proton, supernucleophiles, tautomerism, Wheland intermediate, X-ray diffraction.

Affiliation:

Department of Industrial Chemistry ‘Toso Montanari’, Alma Mater Studiorum - Universita di Bologna, Viale del Risorgimento, 4 - 40136 Bologna Italy.



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