Csp2Csp2

Csp2Csp2 is a designation used in chemical notation to denote a covalent bond between two carbon atoms, each with sp2 hybridization. This situation is common in many unsaturated hydrocarbons, including alkenes and aromatic systems, where carbons involved in the bond are arranged in a plane.

The sp2 hybridization implies that each carbon forms three sigma bonds using sp2 orbitals, arranged in a roughly trigonal planar geometry with about 120-degree angles. The remaining unhybridized p orbital on each carbon participates in a pi system, which in alkenes contributes to the C=C bond and in aromatics participates in extended conjugation. The Csp2Csp2 sigma bond is formed by overlap of the sp2 hybrids from the two carbons and is generally shorter and stronger than a typical C−C single bond due to the higher s-character of the sp2 orbitals.

In terms of context, two sp2 carbons connected by a single Csp2Csp2 bond may be part of a larger conjugated system, where rotation about the bond is hindered by resonance. In alkenes such as ethene, the Csp2Csp2 sigma bond is the sigma component of a C=C double bond, with the pi bond providing the second linkage and restricting rotation. In aromatic rings like benzene, adjacent sp2 carbons are connected by Csp2Csp2 sigma bonds that form part of a delocalized π network, contributing to the planarity and rigidity of the structure.

Overall, Csp2Csp2 describes a common bonding situation that underpins much of organic chemistry, reflecting the planar geometry and enhanced bond strength associated with sp2 hybridization.