sp2centra

Sp2centra is a term used in chemistry to describe atoms in a molecule that are sp2-hybridized. An sp2 center uses three sp2 hybrid orbitals to form sigma bonds and may bear a lone pair, leaving one unhybridized p orbital for pi bonding. This arrangement gives a trigonal planar geometry with bond angles close to 120 degrees, and the center lies in a single plane with its substituents.

Common examples include carbon atoms in alkenes (C=C) and in carbonyl groups (C=O) such as aldehydes, ketones, esters, and other carboxylic derivatives, as well as carbons in imines (C=N). Nitrogen or oxygen can also be sp2 in certain conjugated systems or functional groups. The presence of a pi system means that sp2centra are often involved in resonance and conjugation, contributing to flat, extended structures.

Spectroscopically, sp2 centers show characteristic signals: 13C NMR shifts for sp2 carbons typically fall roughly in the range of 100–160 ppm (carbonyl carbons can resonate further downfield, around 160–200 ppm). Infrared spectroscopy can reveal C=C or C=O stretching modes associated with sp2 centers, and X-ray crystallography can confirm planarity around the center.

Reactivity is dominated by the pi bond: sp2centra participate in electrophilic additions to alkenes, nucleophilic additions to carbonyls, and various conjugation processes in aromatic and polyenes. The planarity and double-bond character influence molecular rigidity, electronic properties, and reaction pathways.

In summary, sp2centra denotes atoms with sp2 hybridization that create planar, pi-bonded centers central to the chemistry of many organic functional groups and materials.