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The s character rich O σ(out) lone pair orbital (also notated n O (σ)) is an ~sp 0.7 hybrid (~40% p character, 60% s character), while the p lone pair orbital (also notated n O (π)) consists of 100% p character. Both models are of value and represent the same total electron density, with the orbitals related by a unitary transformation.
This trend has been attributed to the amount of p-character on the nitrogen lone pair orbital - the higher p character corresponding to a greater nucleophilicity because the p-orbital would allow for donation into the alkene π- orbital. Analogously, if the N lone pair participates in stereoelectronic interactions on the amine moiety, the lone ...
The smallest singlet-triplet gap was calculated to be 8.2 kcal/mol for Me3Si-B. Aminoborylene (H 2 NB) is a slight exception to the above paradigm, as the nitrogen lone pair donates into an unoccupied boron p orbital. Thus, there is formally a double bond between boron and nitrogen; the π* combination of this interaction serves as the LUMO+1. [17]
However lone pairs do not always participate in a conjugated system. For example, in pyridine, the nitrogen atom already participates in the conjugated system through a formal double bond with an adjacent carbon, so the lone pair remains in the plane of the ring in an sp 2 hybrid orbital and does not participate in the conjugation. A ...
The 1b 1 MO is a lone pair, while the 3a 1, 1b 2 and 2a 1 MO's can be localized to give two O−H bonds and an in-plane lone pair. [30] This MO treatment of water does not have two equivalent rabbit ear lone pairs. [31] Hydrogen sulfide (H 2 S) too has a C 2v symmetry with 8 valence electrons but the bending angle is only 92°.
The original 1994 Denk at al. photoelectron spectroscopy communication relates this orbital to the π 2 diimine orbital, however a 1996 paper from Blakeman et al. designates this as the nitrogen lone pairs. Either way, both orbital assignments are symmetrically forbidden from overlapping with any Si orbital.
In the simplest case, the linear N–H molecule (imidogen) has its nitrogen atom sp hybridized, with two of its four non-bonded electrons as a lone pair in an sp orbital and the other two occupying a degenerate pair of p orbitals.
Bent's rule can be extended to rationalize the hybridization of nonbonding orbitals as well. On the one hand, a lone pair (an occupied nonbonding orbital) can be thought of as the limiting case of an electropositive substituent, with electron density completely polarized towards the central atom.