Exploratory Topological Study of the Laplacian of the Electronic Charge Density in n-Butonium Cations

LOBAYAN, R.; SOSA, G. L.; JUBERT, A. H.; NELIDA MARIA PERUCHENA

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: American Chemical Society Publ; Año: 2004 vol. 108 p. 4347 - 4356

1089-5639

In this work we present a systematic HF/6-311++G** study of the topology of the Laplacian of the electronic density for the 11 carbocations, generated upon the insertion of a proton into the C-C or C-H bonds during the protonation of n-butane, two 2-C-n-butonium, three 1-C-n-butonium, three 2-H-n-butonium and three 1-H-n-butonium. It is the continuation of a previous one where the charge density topology of n-butoniums at the same level of approach was studied. The Laplacian charge concentration critical points at each valence shell of carbon atoms are analyzed and also both the charge concentration and the charge depletion critical points closer to hydrogen atoms are studied. Our exploratory analysis shows that the study of the Laplacian topology of the electronic density would be used as a suitable tool in order to quantify the displacement effects of the electronic density through the sigma bonds, the delocalization of the positive charge (in our case introduced into the system by a proton) and the degree of electronic deficiency of the Carbon atom. It is demonstrated here how these facts allow us to understand the stability order found in the studied carbocationic species: 2-C-n-butoniums  > 1-C-n-butoniums  >  2-H-n-butoniums  >  1-H-n-butoniums.