Orbital hybridization: a key electronic factor in control of structure and reactivity

Abstract

This review outlines fundamental factors responsible for hybridization trends in organic and main group compounds. Hybridization is a classic chemical concept that transcends textbook organic chemistry. Hybridization effects are omnipresent, and their understanding is essential for the unraveling of many structural and reactivity puzzles. Even when they are masked by a stronger effect (e.g., allylic delocalization), they still lurk below the surface. Overriding such effects comes with a penalty, whereas incorporation into reaction design provides an efficient tool for the control of reactivity.

The electronic mechanism ruling the dihydrogen bonds and halogen bonds in weakly bound systems of H3SiH···HOX and H3SiH···XOH (X = F, Cl, and Br)

“…in opposition to this, the frequency shifts observed in these bonds are from red nature. Regarding these results, they can be supported by the Bent's rule [99][100][101] of the chemical bond by which is affirmed that s-character of the hybrid orbitals is related to the contribution of the electropositive group or element. Although used successfully in recent intermolecular studies [49,73], we would like to consider that this conception of hybrid orbital enhancements should be used with some caution because some inconsistencies were found in this current research.…”

Heteroatom Substitution at Amide Nitrogen—Resonance Reduction and HERON Reactions of Anomeric Amides

“…This is likely to be a manifestation of the role of orbital size since the influence of second period elements is significant; nitrogen increases p-character in the bond to sulphur to effect better overlap with the larger, 3p orbital of sulphur. Consequently, the nitrogen lone pair gains more “s” character relative to the amide nitrogen in the NNO acetamide 15c , resulting in less amide resonance [36,37,70]. Comparing the M06 values, ONCl and ONO systems have about half the resonance of N , N -dimethylacetamide while NNO, NNCl, and ONS systems are computed to preserve some 60 to 70% of the resonance of N , N -dimethylacetamide.…”

Nitrenium Ion Analogues of Nonclassical Carbocations: Cyclopropylnitrenium, Allylnitrenium, and Azetidenium Ions and Mechanisms for Their Interconversion

“…To assess the feasibility of applying this methodology to larger nitrenium ions in the future, M06-2X results are compared to those from a more expensive, and accurate, complete basis set procedure (CBS-QB3) developed by Petersson et al 36 which provides excellent thermochemical predictions for cationic intermediates. 37 However, because it employs a geometry optimization different from that used in the M06-2X calculations, CBS-QB3 energies are not available for some transition states and shallow local minima. Singlet States.…”