singlebond

Single bond, in chemistry often written as a single covalent bond, is a chemical bond formed when two atoms share one pair of electrons. The bond is typically a sigma bond, produced by end-to-end overlap of atomic orbitals along the bond axis. Its bond order is 1, meaning a single shared electron pair holds the two atoms together. Bond strength and length vary with the atoms involved; for example, C–C single bonds are commonly about 1.54 Å long with bond energies around 340–350 kJ/mol, while H–H is about 436 kJ/mol.

A defining property of single bonds is that they permit rotation about the bond axis in many molecules, giving rise to different conformations such as staggered and eclipsed forms in acyclic alkanes. In some cases, rotation is hindered by steric clashes, conjugation, or rigid ring structures, which can restrict or fix certain conformations.

Hybridization often associated with single bonds is sp3, leading to approximately tetrahedral geometry with bond angles near 109.5°. Single bonds also occur between other types of atoms (e.g., C–N, C–O, C–X) and form the backbone of many saturated compounds, such as alkanes, along with molecules containing multiple single bonds.

Relationship to multiple bonds is a key contrast: double and triple bonds include pi components in addition to sigma bonds, are shorter, and restrict rotation. Single bonds can be broken by homolytic or heterolytic cleavage during chemical reactions, enabling radical or ionic pathways. In summary, a single bond represents the basic, rotatable covalent linkage characterized by a single shared electron pair.