All About Stereochemistry in Cyclic Systems

Stereochemistry is the study of the three-dimensional structure of a molecule. The only structural variation between the cis and trans isomers is the orientation of the molecule’s atoms in three dimensions. 

Stereoisomers have different physical and chemical properties. The cis and trans isomers of butenedioic acid, for example, have significantly different physical and chemical properties.

Cyclic compounds are often known as ring compounds. Cyclic compounds are ones in which one or more atoms form a connection to create a closed ring, as their second name implies.

These compounds have an interesting property when their stereogenic centres are equivalent. In this case, there is at least one plane of symmetry.

What is Stereochemistry?

Stereochemistry dates back to 1842. A French chemist named Louis Pasteur found that salts of tartaric acid extracted from a wine-making vessel may rotate plane-polarised light, although identical salts from different sources cannot. The entire phenomenon is optical isomerism.

It is the study of three-dimensional molecule conformation. It has nothing to do with the number of atoms present or the order of their connection. Instead, it is all about the direction in which those connections point.

Stereochemistry, like conformational analysis (a sub-branch of stereochemistry), has its own vocabulary.

This definition of stereochemistry processes allows any chemist to work out the interactions between different compounds of the same category of atoms. 

They can even look at how these interactions alter a molecule’s physical or biological properties. The study of chiral compounds is an integral part of stereochemistry, and it is an important part of chemistry for students who will require it in the future. 

Types of Stereoisomers

• Atropisomers 

Any molecule or item that is non-superimposable on its mirror image is said to have atropisomerism. Example: Atropisomers of 6,6′-dinitro-2,2′-diphenic acid

• Cis-Trans Isomers 

The same atoms are joined in the same way but in a different configuration in cis-trans isomerism. Example: But-2-ene

Cis-but-2-ene trans-but-2-ene

• Conformational Isomers 

Technically single bond rotations can only transform isomers in conformational isomerism.

Example : Rotation about a single bond of butane to interconvert one conformation to another.

• Diastereomers

Isomers that are not enantiomers have more optically active diastereomers. They aren’t identical stereoisomers, don’t have mirror images, and you can’t superimpose them on one another. 

Diastereomers include cis and trans-2-butene, D-threose and D-erythrose, 2-chloro,3-bromobutane, and 2-chloro,3-bromobutane.

D-threose D-erythrose

• Enantiomers

One of two optical isomers, enantiomers are structures that one cannot superimpose on their mirror copies. Example,(S)-(+)-lactic acid (left) and (R)-(–)-lactic acid (right) are nonsuperimposable mirror images of each other.

(S)-(+)-lactic acid (R)-(–)-lactic acid

 When a carbon atom has four distinct groups bonded to it, this is the most prevalent sort of “chirality” (so it must be sp3 hybridised). A chirality centre is subsequently assigned to this carbon atom. 

Scholars used the phrases chiral, asymmetric, and stereogenic centre in the past. A stereocenter is another term for the latter phrase.

Besides their interactions with plane polarised light or other chiral compounds, enantiomers have the same chemical and physical properties (melting temperatures, boiling points, heat of combustion, reagents, solvents, catalysts, etc.).

Stereochemistry of Organic Compounds

The study of stereoisomers is known as stereochemistry. It includes all elements of organic, inorganic, biological, physical, and supramolecular chemistry. Stereochemistry is the study of how to determine and describe these relationships and how they affect physical and biological features.

Organic compounds contain carbon and other elements necessary for living beings to reproduce. Carbon is the most significant component because it has four electrons and can fit eight in an outer shell. As a result, several sorts of bonds with other carbon atoms and elements such as hydrogen, oxygen, and nitrogen are possible. 

Hydrocarbons and proteins are organic molecules capable of forming long chains and complex structures.

The organic components of these molecules constitute the basis for chemical reactions in plant and animal cells, providing the energy required to obtain food, reproduce, and execute other life-related tasks.

• Acyclic or Open Chain Compound 

Aliphatic chemicals have branching or straight chains and are also known as aliphatic compounds. Ethane and Isobutane are examples of open chain compounds.

• Aromatic Compound

They are unique compounds that contain benzene and other ring-related chemicals. They can have heteroatoms in the ring, just like alicyclic compounds. They are known as heterocyclic aromatic compounds. Benzene,Toluene and Aniline are aromatic compounds.

• Alicyclic or Closed Chain or Ring Compounds 

These compounds are cyclic, which means their carbon atoms are arranged in a ring (homocyclic). When atoms other than carbon are present, it is called heterocyclic. Cyclohexane and Cyclopentane are closed chain compounds.

Conclusion

Homocyclic compounds are cyclic compounds with a ring structure generated by the atoms, as opposed to heterocyclic compounds with a ring structure formed by the atoms. The atoms in this ring structure are all from the same element, carbon. They’re known as carbocyclic compounds.

Stereochemistry is a field of chemistry that studies and manipulates the relative spatial arrangement of atoms that make up a molecule’s structure. As a result, it’s sometimes referred to as 3D chemistry, with “stereo” standing for “three-dimensionality.”

Dynamic stereochemistry is another branch of stereochemistry that deals with three-dimensional chemistry. It studies how varied spatial arrangements of atoms in a molecule affect the rate of a chemical reaction.