The Tendency for Catenation

In simple terms, “catenation” is related to the self-linking of an element’s atoms to form chains and rings.

Catenation is the process of chemical bonding between groups of atoms of the same element that happens only between atoms of an element with a valency of at least two and produces rather strong bonds with itself. This idea can encompass the formation of layers, such as two-dimensional catenation, and spatial lattices, such as three-dimensional catenation.

This feature is more noticeable in silicon and sulfur atoms, and it is most prevalent in carbon atoms. It is just faintly present in nitrogen, germanium, tellurium, and selenium atoms.

Examples of Catenation

The most common catenation examples are:

• Boron
• Carbon
• Sulfur
• Silicon

Catenation of carbon is quite common, where it forms covalent connections with other carbon atoms to form extensive chains. This is why nature contains such a large variety of organic chemicals. Carbon is best known for its catenation capabilities when it comes to understanding catenated carbon structures. 

However, carbon is far from the only element capable of creating such catenae. Silicon, sulfur, and boron are just a few of the main group elements that can generate a variety of catenae.

Catenation Property in Group 4

Catenation is a feature shared by all elements of the carbon family, sometimes known as Group 4. The family’s first member has the greatest proclivity to catenate.

The following is the tendency to catenate:

C > Si > Ge > Sn > Pb

The likelihood for catenation reduces as one moves down the group. This occurs as the atomic size decreases as the group progresses, reducing the strength of the covalent bond. As a result, the catenation property reduces as the group grows. The following is the catenation tendency in C, Si, and Ge:

Ge < Si < C

Ge has the lowest bond energy, and so it also has the lowest catenation propensity. Additionally, as the size and duration of the connection increase, the catenation propensity decreases.

Occurrence

• Carbon

With carbon atoms, catenation is easier, resulting in covalent bonds with more carbon atoms, resulting in structures and longer chains. This is the main reason for the large number of organic molecules found in nature.

Catenation of carbon properties are well-known, and organic chemistry is mostly concerned with the study of catenated carbon structures (also referred to as “catenae”). Carbon chains in biochemistry combine any other element onto the backbone of carbon, such as oxygen, biometals, and hydrogen.

The capacity to catenate is determined by an element’s binding energy to itself, which lowers when more dispersed orbitals (those with a higher azimuthal quantum number) overlap to form the bond. Lighter elements with larger valence shell orbitals create longer p-p sigma linked atom chains than carbon, which has the smallest diffuse valence shell p-orbital.

A mixture of electronic and steric variables, such as the element’s electronegativity, the molecular orbital n, and the capacity to form different types of covalent bonds, determine the ability to catenate. The sigma mismatch between neighbouring atoms is large enough for completely stable carbon chains to develop. Despite a mountain of evidence to the contrary, it was once considered that the other aspects would make it more difficult.

• Hydrogen

The 3-dimensional networks of chains and rings, as well as tetrahedra, which are joined via hydrogen bonding, make up the structure of the water theory.

In 2008, a polycatenated network was developed, comprising rings made from metal-templated hemispheres joined by hydrogen bonds.

Hydrogen bonding is known for aiding the formation of chain structures. For example, 4-tricyclanol C10H16O and crystalline isophthalic acid – C8H6O4 is made up of molecules united by hydrogen bonds, resulting in helical and endless chains.

The carbon nanotube is projected to become metallic at relatively low pressure, 163.5GPa, amidst the peculiar conditions of a one-dimensional succession of hydrogen molecules trapped within a single wall. This is up to 40% of the 400GPa pressure anticipated to be required to metalize ordinary hydrogen, a pressure that can be difficult to obtain experimentally.

• Silicon

Silicon atoms form sigma bonds with other silicon atoms (disilane is the parent of this compound’s class). However, preparing and isolating SinH2n+2 (which is equivalent to saturated alkane hydrocarbons) with n higher than or equal to 8 is difficult since their thermal stability declines as the number of silicon atoms grow.

Silanes break down to hydrogen and polymeric polysilicon hydride, which have a larger molecular weight than disilane. However, by substituting an appropriate pair of organic substituents on each silicon in place of hydrogen. 

Even silicon-silicon pi bonding is feasible. However, these bonds are less stable than carbon equivalents. Disilane is a far more reactive substance than ethane. Unlike alkynes and alkenes, disilynes and disilene are extremely rare. Disilynes, for example, has long been regarded to be too unstable to be isolated.

Conclusion 

In this article, we’ve covered the meaning, example, occurrences, and more about catenation. Catenation is shown in carbon and silicon both but carbon has more tendency for catenation due to small size.