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In organic chemistry, neighbouring group participation (NGP, also known as anchimeric assistance) has been defined by the International Union of Pure and Applied Chemistry (IUPAC) as the interaction of a reaction centre with a lone pair of electrons in an atom or the electrons present in a sigma or pi bond contained within the parent molecule but not conjugated with the reaction centre.
The σ-symmetry lone pair (σ(out)) is formed from a hybrid orbital that mixes 2s and 2p character, while the π-symmetry lone pair (p) is of exclusive 2p orbital parentage. 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 ...
For instance, the lone pairs of water are usually treated as two equivalent sp x hybrid orbitals, while the corresponding "nonbonding" orbitals of carbenes are generally treated as a filled σ(out) orbital and an unfilled pure p orbital, even though the lone pairs of water could be described analogously by filled σ(out) and p orbitals (for ...
Gillespie terms the lone pair a lone pair domain and states that these lone pair domains push the ligands together until they reach the interligand distance predicted by the relevant inter-ligand radii. [1] An example demonstrating this is shown below, where the F-F distance is the same in the AF 3 and AF 4 + species :
For example, NH 3 is a Lewis base, because it can donate its lone pair of electrons. Trimethylborane [(CH 3 ) 3 B] is a Lewis acid as it is capable of accepting a lone pair. In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. [ 1 ]
[5] [22] For instance, a modification of this analysis is still viable, even if the lone pairs of H 2 O are considered to be inequivalent by virtue of their symmetry (i.e., only s, and in-plane p x and p y oxygen AOs are hybridized to form the two O-H bonding orbitals σ O-H and lone pair n O (σ), while p z becomes an inequivalent pure p ...
There are several variants of bending, where the most common is AX 2 E 2 where two covalent bonds and two lone pairs of the central atom (A) form a complete 8-electron shell. They have central angles from 104° to 109.5°, where the latter is consistent with a simplistic theory which predicts the tetrahedral symmetry of four sp 3 hybridised ...
The oxygen atom’s two lone pairs interact with a hydrogen each, forming two additional hydrogen bonds, and the second hydrogen atom also interacts with a neighbouring oxygen. Intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C) compared to the other group 16 hydrides , which have little capability to ...