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.

Trends in hybridization were systematically analyzed through the combination of DFT calculations with NBO analysis for the five elements X (X = B, C, N, O, and F) in 75 HnX-YHm compounds, where Y spans the groups 13-17 of the periods 2-4. This set of substrates probes the flexibility of the hybridization at five atoms X through variations in electronegativity, polarizability, and orbital size of Y. The results illustrate the scope and limitations of the Bent's rule, the classic correlation between electronegativity and hybridization, commonly used in analyzing structural effects in carbon compounds. The rehybridization effects are larger for fluorine- and oxygen-bonds than they are in the similar bonds to carbon. For bonds with the larger elements Y of the lower periods, trends in orbital hybridization depend strongly on both electronegativity and orbital size. For charged species, the effects of substituent orbital size in the more polarizable bonds to heavier elements show a particularly strong response to the charge introduction at the central atom. In the final section, we provide an example of the interplay between hybridization effects with molecular structure and reactivity. In particular, the ability to change hybridization without changes in polarization provides an alternative way to control structure and reactivity, as illustrated by the strong correlation of strain in monosubstituted cyclopropanes with hybridization in the bond to the substituent.

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FIGURE 7 Discharge power, pH, and liquid conductivity after discharge, as well as H 2 O 2 concentration for both gas and liquid scavengers. The liquid and gas flow rates were 0.75 ml min −1 and 0.4 L min −1 . For the pure water cases the discharge power, pH, liquid conductivity after discharge, and H 2 O 2 concentration were 0.6 W, 5.2, 12 µS cm −1 , 9.1 × 10 −8 mol s −1 for gas, and 9.8 × 10 −8 mol s −1 for liquid HSIEH ET AL.

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