English
Noun
catenation- the property of a few elements, most especially carbon, to yield chains and rings by forming covalent bonds with atoms of the same element
User Contributed Dictionary
Extensive Definition
Catenation is the ability of a chemical
element to form covalent
bonds with itself, resulting in ring, chain and cage
structures. The element most well known for its catenation is
carbon, with organic
chemistry being essentially the study of catenated carbon
structures (otherwise known as catenae). However, carbon is by no
means the only element capable of forming such catenae, and several
other main group elements are capable of forming an expansive range
of catenae.
The ability of an element to catenate is
primarily based on the bond energy
of the element to itself. This ability is also influenced by a
range of steric and electronic factors, including the electronegativity
of the element in question, the molecular
orbital hybridization and the ability to form different kinds
of covalent bonds. For example, carbon has the ability to form both
sigma and pi bonds to itself. This is due to an overlap between
pi-electron orbitals, allowing electron density to be shared and
thus stabilising the bond. Silicon, on the
other hand, has negligible overlap between pi-orbitals, and thus
tends to not form pi-bonds by preference. As a result, silicon has
a relatively poor capacity for catenation.
Silicon can form sigma bonds to other silicon
atoms (disilane is the
parent of this class of compounds). Even silicon–silicon pi bonds
are possible. However, these bonds are less stable than the carbon
analogs. Disilane is quite
reactive compared to ethane. Disilylenes are quite
rare, unlike alkenes. And
disilynes, unlike
alkynes, are too unstable
to be isolated except (possibly) for specially designed molecular
structures.
The ability of certain main group elements to
catenate is currently the subject of research into inorganic
polymers.