Topological electron density properties at critical points along aromatic rings as reactivity and regioselectivity descriptors in electrophilic substitutions

Abstract

In order to evaluate the substituent effect on the reactivity and regioselectivity of aromatic rings with respect to electrophilic substitution reactions, we considered several benzene derivatives containing activating (ÀNH 2 , ÀNHCH 3 , ÀN(CH 3 ) 2 , ÀOH, ÀOCH 3 , and ÀCHCH 2 ) and deactivating (ÀF, ÀCl, ÀBr, ÀCOH, ÀCOCH 3 , ÀCOOCH 3 , ÀCOOH, ÀCOCl, ÀCN, and ÀNO 2 ) groups. In this sense, we propose alternative theoretical descriptors of reactivity and regioselectivity, which are based only on electron density properties of initial substrates. The descriptors investigated here were obtained from the quantum theory of atoms in molecules (electron density curvatures at the ring critical point [RCP] and at the critical points of carbon nuclei along with kinetic and potential energy densities at the RCP) and from the interacting quantum atom formalism (intra-atomic energy values of carbon atoms). The topological parameters at the RCPs and at carbon nuclei within the aromatic moiety were particularly successful in this task, being able to provide quantitative predictions of reactivity as compared with traditional resonance parameters used to that same end.

Interacting Quantum Atoms and Multipolar Electrostatic Study of XH···π Interactions

“…However, no orbitals are directly involved in the context of REG-IQF or REG-MULTI because QTAIM, and thus IQA, is an orbital-invariant method. , Incidentally, one can argue that it is actually incorrect to give an orbital-based name (π) to an interaction that can be explained without referring to orbitals, as we do here. More results on the interactions between aromatic compounds and ions seem to point in the same direction: strong quadrupole–charge interactions are reported by several studies, where the strength of the electrostatic interactions in those systems plays an essential role in the enantioselectivity. – Moreover, the quadrupolar electrostatics of carbon atoms of aromatic rings have been demonstrated to be proper descriptors of aromatic electrophilic substitution reactions, thereby strengthening the importance of the development of methods to understand electrostatic effects in such context. , …”

“…52−54 Moreover, the quadrupolar electrostatics of carbon atoms of aromatic rings have been demonstrated to be proper descriptors of aromatic electrophilic substitution reactions, thereby strengthening the importance of the development of methods to understand electrostatic effects in such context. 55,56 Furthermore, two major points follow from the REG-IQF-D3 analysis. The first is the intramonomeric role of X−H (X = O, N), where its electrostatic energy helps the formation of the complex and its covalent energy thwarts it.…”

“… 53 – 55 Moreover, the quadrupolar electrostatics of carbon atoms of aromatic rings have been demonstrated to be proper descriptors of aromatic electrophilic substitution reactions, thereby strengthening the importance of the development of methods to understand electrostatic effects in such context. 56 , 57 …”

Isolation of an organometallic yttrium bismuth cluster and elucidation of its electronic structure

“…The lack of electron delocalisation is reflected in the curvature of electron density perpendicular to the ring critical points (RCPs, l p3 ) of the cubane faces, which is two orders of magnitude smaller than the value found for benzene. 20,21 The associated Mayer bond indices (MBOs) clarify the bond strengths, where values B1 are calculated for each Bi-Bi bond and B0.5 for each Y-Bi bond.…”