Description of the Acid/Base Behavior of Organic Phosphines Using ab initio and Chemometric Approaches

Abstract

The concept FERMO emerges as a tool to investigate the role of molecular orbitals used to describe the chemical bonds. Thus, calculations were carried out with a set of phosphines. Our data suggest that different molecular orbitals, beyond HOMO, can be used to describe the behavior of acid-base reactions.

Orbital Signatures as a Descriptor of Regioselectivity and Chemical Reactivity: The Role of the Frontier Orbitals on 1,3-Dipolar Cycloadditions

“…15,16 The MO shape and the atomic composition are very important parameters for analyzing FERMO. [17][18][19][20][21] Upon analyzing orbital localization and composition more deeply (Table 4), we can observe that there is an MO with energy quite close to the HOMO energy value and with a large contribution of the atoms present at the active site (APAS: 1, 2, 3, 4 and 5, see Figure 1). For the reactions A, B, C, and D the APAS contributions (%) were 78.58, 69.77, 91.10, and 77.34, respectively.…”

“…In this concept, the FERMO provides the adequate orbital shape and composition to correlate with reactive indexes. [15][16][17][18][19][20][21] It is important to mention that, in general, the reactivity indexes involving molecular orbitals are obtained from theoretical static calculation. However, the thermal effects might play an important role on the chemical reactivity.…”

“…The concept of the frontier orbital, introduced by Fukui around 1952, relates reactivity with the properties of two molecular orbitals: HOMO and LUMO. In fact, one application of the HOMO−LUMO argument is the description of the cycloaddition reactions. − It should be kept in mind, however, that the HOMO−LUMO argument has certain limitations and new efforts are necessary to understand when the HOMO energy works and when it does not; currently, that important topic in chemistry has been the target of several research groups. − More recently, the frontier effective-for-reaction molecular orbital (FERMO) concept has emerged as a powerful approach for studying this situation. − The localization and the composition of the orbitals can reveal a frontier molecular orbital close to the HOMO with large contribution in atoms present at the active site (APAS). Actually, a large MO contribution in APAS can fit our orbital choice criterion, because they are common to all of the studied compounds and are mainly located where the reaction takes place.…”

“…Therefore, this special orbital will be called FERMO. In this concept, the FERMO provides the adequate orbital shape and composition to correlate with reactive indexes. − …”

Rationalizing the regioselectivity of substituted phenols from the FERMO concept: stereoelectronic effects on protonation and functionalization

“…Even though these studies have shown the existence of several protonated isomers of many aromatic ions, and in some cases also the specific locations of the protons, the details of their structures constantly remained confused. For these cases, the structural attribution of the various isomers sometimes depended on computational chemical calculations [14,15,36,37].…”