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According to the sigma bond rule, the number of sigma bonds in a molecule is equivalent to the number of atoms plus the number of rings minus one. N σ = N atoms + N rings − 1. This rule is a special-case application of the Euler characteristic of the graph which represents the molecule. A molecule with no rings can be represented as a tree ...
This MO is called the bonding orbital and its energy is lower than that of the original atomic orbitals. A bond involving molecular orbitals which are symmetric with respect to any rotation around the bond axis is called a sigma bond (σ-bond). If the phase cycles once while rotating round the axis, the bond is a pi bond (π-bond).
Sigmatropic rearrangements are concisely described by an order term [i,j], which is defined as the migration of a σ-bond adjacent to one or more π systems to a new position (i−1) and (j−1) atoms removed from the original location of the σ-bond. [3]
A double bond has two shared pairs of electrons, one in a sigma bond and one in a pi bond with electron density concentrated on two opposite sides of the internuclear axis. A triple bond consists of three shared electron pairs, forming one sigma and two pi bonds. An example is nitrogen.
The reaction center can be a p-or sp n-orbital (Woodward-Hoffmann symbol ω), a conjugated system (π) or even a sigma bond (σ). The relationship is antarafacial when opposite faces of the π system or isolated orbital are involved in the process (think anti). For a σ bond, it corresponds to involvement of one "interior" lobe and one ...
For example, a bond between two s-orbital electrons is a sigma bond, because two spheres are always coaxial. In terms of bond order, single bonds have one sigma bond, double bonds consist of one sigma bond and one pi bond, and triple bonds contain one sigma bond and two pi bonds. However, the atomic orbitals for bonding may be hybrids.
In chemistry, sigma hole interactions (or σ-hole interactions) are a family of intermolecular forces that can occur between several classes of molecules and arise from an energetically stabilizing interaction between a positively-charged site, termed a sigma hole, and a negatively-charged site, typically a lone pair, on different atoms that are not covalently bonded to each other. [1]
The carbon–carbon single bond is a sigma bond and is formed between one hybridized orbital from each of the carbon atoms. In ethane, the orbitals are sp 3-hybridized orbitals, but single bonds formed between carbon atoms with other hybridizations do occur (e.g. sp 2 to sp 2). In fact, the carbon atoms in the single bond need not be of the ...