Charge-based DFT descriptors for Diels-Alder reactions

Abstract

The geometries of 8 dienes and 18 dienophiles are optimized at the B3LYP/6-311 + G (d) level. The ionization potential (I), electron affinity (A), electronegativity (χ), hardness (η), chemical potential (μ), global electrophilicity (ω), electron accepting power (ω+) and electron donating power (ω−) values are computed employing ΔSCF method. The net reactivity index (Δurn:x-wiley:08943230:media:poc2987:poc2987-math-0001), electrophilicity difference of the reactants (Δω), the fractional number of electrons transferred (ΔN), energy change (ΔE) and electrophilicity-based charge transfer descriptor (ECT) for the Diels-Alder (DA) reactions are computed. Charge-based descriptors like ΔN, ΔE and ECT exhibit good quadratic / linear correlation with urn:x-wiley:08943230:media:poc2987:poc2987-math-0002 of the diene to dienophile electron flow (DDpF) type of DA reactions. Δω has also reasonably good quadratic / linear correlation with ΔN, ΔE ECT andurn:x-wiley:08943230:media:poc2987:poc2987-math-0003. Charge-based descriptors like ΔN, ΔE and ECT have relatively worse correlation (quadratic / linear) with urn:x-wiley:08943230:media:poc2987:poc2987-math-0004 of the dienophile to diene electron flow (DpDF) type of DA reactions. Δω has also similar poor correlation (quadratic / linear) with ΔN, ΔE, ECT and urn:x-wiley:08943230:media:poc2987:poc2987-math-0005 for these types of reactions. It can be concluded that charge-based Density Functional Theory (DFT) descriptors can illustrate the DDpF type of DA reactions properly. A possible reason for not so good correlation in the case of DpDF-type reactions is provided. The charges of the reactive sites of the dienes and dienophiles are also computed with the Mulliken population analysis and natural population analysis schemes at the same level of theory.