Dhristi JEE 2022-24

Definition of Catenation

Catenation meaning or the catenation in chemistry is defined as a chemical linkage into the chains of atoms of a similar element, by only occurring among the atoms of an element, which contains a valence of at least two and that produces the relatively strong bonds with itself. This property is significant among the silicon and sulfur atoms, predominant among the carbon atoms, and slightly present among the atoms of nitrogen, germanium, tellurium, and selenium.


Occurrence

Carbon

Catenation takes place most readily with the carbon atoms, which produces the covalent bonds with the other carbon atoms to form structures and longer chains. This is the main reason for the presence of a huge number of organic compounds in nature. Carbon is well-known for its catenation properties, with organic chemistry importantly being the study of catenated carbon structures (also referred to as catenae). In biochemistry, carbon chains combine any of the different other elements, such as oxygen, biometals, and hydrogen, onto the backbone of carbon.


But, by no means carbon is described as the only element that is capable of forming such catenae, and the many other main-group elements are capable of producing an expansive range of catenae, including boron, hydrogen, phosphorus, sulfur, and silicon.


The element's ability to catenate is essentially determined by its bond energy to itself, which decreases as more dispersed orbitals (those with a higher azimuthal quantum number) overlap to form the bond. As a consequence, the carbon element, which has the least or minimal diffuse valence shell p-orbital, will form the longer p-p sigma bound chains of atoms compared to the heavier elements, which have higher valence shell orbitals.


The ability to catenate is influenced further by a combination of electronic and steric influences, such as the element's electronegativity, the molecular orbital n, and the ability to form different forms of covalent bonds. For the carbon atom, the sigma overlap between the adjacent atoms is strong enough that perfectly stable chains are formed. With the other elements, this was once thought to be not easier despite plenty of evidence to the contrary.


Hydrogen

The structure of the water theories involves the 3-dimensional networks of both chains and rings, and tetrahedra, which are linked via hydrogen bonding. A polycatenated network, with the rings produced from metal-templated hemispheres, which are linked by the hydrogen bonds, was reported in 2008.


In organic chemistry, hydrogen bonding is well known to facilitate the formation of chain structures. For example, 4-tricyclene C10H16O represents catenated hydrogen bonding between the hydroxyl groups by leading to the production of helical chains; crystalline isophthalic acid - C8H6O4 is built up from the molecules, which are connected by the hydrogen bonds, forming infinite chains.


Whereas in the unusual conditions, a one-dimensional series of hydrogen molecules confined within a single wall, the carbon nanotube can be expected to become metallic at relatively low pressure, at 163.5 GPa. This is up to 40% of the ~400 GPa thought to be needed to metalize ordinary hydrogen, a pressure that can be difficult to access experimentally.


Silicon

Silicon forms the sigma bonds to other silicon atoms (where the disilane is given as the parent of this compounds’ class). But, it is not easy to prepare and isolate SinH2n+2 (which is analogous to the saturated alkane hydrocarbons) with n greater than up to 8, as their thermal stability decreases with the increases in the number of silicon atoms. Silanes, which are higher in molecular weight compared to the disilane, decompose to hydrogen and polymeric polysilicon hydride. However, with the suitable pair of the organic substituents on each and every silicon in the place of hydrogen, it is also possible to prepare polysilanes (at times, the erroneous ones are referred to as polysilanes) that can be defined as the analogues of alkanes. These particular long-chain compounds contain surprising electronic properties - of high electrical conductivity, for example, arising from the sigma delocalization of electrons present in the chain.


Even the pi bonds of silicon-silicon are possible. But, these bonds are less stable compared to the carbon analogues. Disilane is quite reactive than ethane. Disilynes and disilene are quite rare, unlike alkynes and alkenes. Examples of disciplines long thought to be too unstable to be isolated, which were reported in 2004.


Example of Catenation

Most of the common examples of elements or catenation that exhibit catenation is given as follows:

  • Carbon

  • Silicon

  • Sulfur

  • Boron

Catenation takes place most readily in carbon by forming the covalent bonds to produce longer structures and chains with the other carbon atoms. This is the reason the huge number of organic compounds are found in nature. In organic chemistry, carbon is the best-known element for its catenation properties, with the analysis of catenated carbon structure.


By no means carbon is the only element capable of forming such catenae; however, and many other main group elements are capable of producing a wide range of catenae, including sulfur, boron, and silicon.


Carbon isn't the only element capable of generating catenae; silicon, sulfur, and boron are just a few examples.

In Group 4, there is a Catenation Property.

Catenation is a trait shared by all members of the carbon family, or group 4. Catenation is most likely to occur in the family's first member.

Catenation tendencies are as follows:

Si > Ge > Sn > Pb > C > Si > Ge > Sn > Pb > C > Si > Ge > S

The proclivity for catenation reduces as one progresses through life.


Atoms and Nuclei

In the 20th century, research on the material world changed to the atomic structure, which is the essence of the material world. In 1897, J.J.J. Thomson discovered the electron by showing that atoms have more elementary particles. Fourteen years later, Rutherford discovered that most of the mass of an atom lies in small nuclei with a radius  100,000 times less than atoms. A ray, on the other hand, turns out to be composed of photons, which correspond to particles in a wave. These discoveries gave birth to new concepts. When these concepts and discoveries are combined, new ideas emerge. The result is a quantum theory. This theory provides a good interpretation of the phenomena in the atomic and subatomic world. In this microscopic world, distances are measured in nanometers and phantom meters.


The electrons in the atoms are held together by the electromagnetic force of the nucleus of the atom. At this level, we need a quantum-mechanical approach to understand the energy states of the electrons in an atom. But I don't have time to discuss this in detail.

 

Quantum Numbers and Atomic Orbitals

Quantum mechanics of the structure of an atom is a mathematical approach that describes the behavior of electrons in atoms. The first is expressed as a wave function, each of which is characterized by a series of numbers. Each set of numbers represents a state, also known as an orbital state. Quantum Numbers and Atomic Orbitals is a page that provides additional information on this topic. The film shows the relationship between the periodic table of the elements and the shape and concept of atomic orbitals. These concepts are necessary to understand bonding. 


For example, bonds formed between carbon atoms in diamond, silicon, graphite, etc. 


Electronic Configuration

The electronic configuration of an element or atom describes the energy state of the electrons in it. Pauli's exclusion principle and Hund's law are some of the theories concerned with the assignment of electron configurations. An electron in a hybrid orbital atom can have multiple orbital properties and have similarities. That is, atomic orbitals can be combined into hybrid orbitals. These hybrid orbitals are especially useful when discussing chemical bonding. For carbon, the hybrid orbitals are made up of the 2s, 2p0, 2p + and 2p orbitals. Orbital 4 separating the symbols s and p is called an sp3 hybrid orbital because orbitals 1s and 3p are used. The shape and orientation of this orbit should have been explained in the lecture, but here we need a diagram. The diamond bond is perfectly explained by the sp3 hybrid orbital. 


Benzene and Graphite Bonds 

Benzene bonds should be discussed in detail in organic chemistry courses. Simply put, the orbital used to form a sigma bond is an sp2 hybrid orbital formed as a combination of 2s, 2p + and 2p orbitals. Also, when 2p0 orbitals overlap, a pi bond is formed. 


Resonance, Benzene and Graphite 

Again, the structure of benzene is a great example of the concept of resonance. If someone claims that the 3 double and 3 single bonds of benzene alternate along the ring, you could start with a single or double bond. Because the six bonds are about the same length, the substructure is a benzene structure. Therefore, the combination of the two structures is used to represent the structure of benzene, and the approach is called resonance. That is, the electrons in the double bond are delocalized throughout the ring. The description of benzene bonds applies to one sheet of graphite. In graphite, electrons are delocalized in two planes. So it's no surprise that graphite is an excellent sheet conductor. 


Buckminster Fullerene 

The graphite structure is the result of the expansion of pi electrons in the plane. Because all the rings in graphite are made up of 6 carbon atoms, the sheet is flat. If the hybrid orbital is somewhat flexible, it is easy to see that a five-membered ring is also possible. However, the formation of pentacyclic rings results in distortions of the planar structure that are not normally considered.

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FAQs (Frequently Asked Questions)

1. Explain the catenation Property in Group 4

All the elements of the group 4 family or carbon family exhibit the catenation property. The first member of this family contains the highest tendency to catenate.


The tendency to catenate is given as follows:

C > Si > Ge > Sn > Pb


The tendency of catenation decreases down the group. This occurs due to the reason the atomic size increases down the group, and also, the strength of the covalent bond decreases. Thus, the catenation property gets decreased down the group.

2. What are Semi-Metallic elements?

In recent years, a number of double and triple bonds between semi-metallic elements such as germanium, silicon, bismuth, arsenic, and others have been published. The ability of such primary group elements to catenate is the research subject into inorganic polymers currently.

3. Why does carbon exhibit a catenation property?

The catenation property of the carbon atom is greater compared to the other elements. Therefore, its bond with the other carbon atom is quite stronger as the shared pair of electrons is quite closer to the nucleus. Therefore, the catenation property is shown by carbon.

4. Give the importance of carbon’s catenation?

Catenation is defined as the linkage of atoms of a similar element into the longer chains. Catenation takes place most readily in carbon, which produces covalent bonds with the other carbon atoms to produce longer structures and chains. This is the main reason for the presence of a huge number of organic compounds in nature.

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