Charge-based DFT descriptors for Diels-Alder reactions

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 (chi), hardness (eta), chemical potential (mu), global electrophilicity (omega), electron accepting power (omega(+)) and electron donating power (omega(-)) values are computed employing Delta SCF method. The net reactivity index (Delta omega(+/-)(R)), electrophilicity difference of the reactants (Delta omega), the fractional number of electrons transferred (Delta N), energy change (Delta E) and electrophilicity-based charge transfer descriptor (ECT) for the Diels-Alder (DA) reactions are computed. Charge-based descriptors like Delta N, Delta E and ECT exhibit good quadratic / linear correlation with Delta omega(+/-)(R) of the diene to dienophile electron flow (DDpF) type of DA reactions. Delta omega has also reasonably good quadratic / linear correlation with Delta N, Delta E ECT and Delta omega(+/-)(R). Charge-based descriptors like Delta N, Delta E and ECT have relatively worse correlation (quadratic / linear) with Delta omega(+/-)(R) of the dienophile to diene electron flow (DpDF) type of DA reactions. Delta omega has also similar poor correlation (quadratic / linear) with Delta N, Delta E, ECT and Delta omega(+/-)(R) 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. Copyright (C) 2012 John Wiley & Sons, Ltd.