Classification of Organic Compounds

What do you know about organic compounds? If we talk about in Chemistry terms, Organic compounds can be defined as any type of chemical compounds in which atoms of carbon, that could be one or more than one, are covalently linked to the other elements’ atoms. In very simple terms, you can say that organic compounds are simply any chemical compounds that have carbon, but it doesn’t mean that every carbon-containing compound can be known as organic, for e.g., cyanides, carbonates and carbides.

The best example of the simplest organic compound is Methane. A few examples of Organic compounds are cyclohexane, ethyne, ethane and ethane.

Classification of Organic Compounds

Organic Compounds can be classified on two bases. Firstly we will talk about organic compounds, which are based on “Structure,” and secondly, we will discuss the organic compounds, which are based on “Function.” Now we will study these classifications of organic compounds in detail.

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1. Classification based on the structure

Let us look at the classification of organic compounds based on structure.

1. Acyclic or open chain compounds

2. Cyclic or closed chain compounds

1. Acyclic or Open-chain Compounds

Acyclic compounds are just opposite to cyclic compounds because their molecules don’t form any ring. It is called open-chain compounds because they have a linear structure. The best examples of these compounds are acyclic aliphatic compounds and alkanes. Open-chain compounds can be understood by straight-chain compounds and branched-chain compounds. The straight-chain compounds don’t have any side chains, but branched-chain compounds’ atoms have the straight chain and one or more than one side chain are attached to it.

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2. Cyclic or Closed-chain Compounds

Cyclic compounds are also known as “Ring compounds.” As its second name suggests, cyclic compounds are those kinds of compounds where one or more than one number of atoms get connected to form a closed ring. It is not mandatory that every ring of these compounds is to be of the same size.

Cyclic or closed-chain compounds always have a prior place in human beings’ day-to-day life as humans encounter these compounds on a daily basis. They are also categorized into two divisions. The first division is about “Heterocyclic,” and the second division is about “Homocyclic.” Now we will discuss these categories one by one.

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1. Heterocyclic compounds

Heterocyclic compounds are a kind of cyclic compound in which the ring structure exists. We can understand these compounds in a very simple definition as it is like any other dominant branch of organic compounds in which two or more two atoms join in the ring shape in their molecules. Although they have atoms of carbon, it must be noticed that at least one atom of another element also exists. The very familiar examples of these compounds are synthetic dyes, nucleic acids and most drugs.

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2. Homocyclic compounds

If we talk about organic chemistry, Homocyclic compounds are the type of cyclic compounds, unlike heterocyclic, in which the ring structure is formed by the atoms. This ring structure is made up of the same elements’ atoms and this element is the carbon. These are called Carbocyclic compounds. No element other than carbon can exist in this compound. Although in inorganic chemistry, homocyclic compounds have ring structures that have been formed by diff-diff elements’ atoms like boron, sulphur, phosphorus and so on. The best examples of this compound are naphthalene, tetracene, benzene and so on.

Heterocyclic Compounds

Heterocyclic compounds are divided into two broad categories, which are named Alicyclic heterocyclic compounds and Aromatic heterocyclic compounds. Now, we will discuss these categories in brief.

Classification of Heterocyclic Compounds

1. Alicyclic Heterocyclic Compounds

We can understand these compounds by simple lines. Ring structures of these compounds have one or more than one heteroatom. We can understand these compounds by a few examples, which are tetrahydrothiophene, tetrahydrofuran and so on.

2. Aromatic Heterocyclic Compounds

These compounds can be easily defined by simple understanding. Unlike Alicyclic heterocyclic compounds, molecules of these compounds have one or more than one heteroatom. Examples of these compounds are thiophene, furan and so on.

Homocyclic or Carbocyclic Compounds

Homocyclic or carbocyclic compounds are basically divided into two compounds. The first compound is known as Alicyclic compound and the second is known as Aromatic compound. Now we will discuss these compounds in detail.

Classification of Homocyclic compounds

1. Alicyclic Compounds

The alicyclic compound is that kind of compound that is aliphatic and cyclic too. This compound has one or more than one all-carbon ring that can be saturated or unsaturated. The bonds which exist in pairs of atoms can be any type of bond like single, double or triple.

2. Aromatic Compounds

Aromatic compounds are those cyclic compounds that are unsaturated, unlike alicyclic compounds, which are either saturated or unsaturated. These compounds are also called aromatics or arenas. They are pleasant in the smell, as their Greek meaning suggests, which is “aroma.” These compounds can be distinguished by one or more than one planar ring of atoms linked by covalent bonds of two different types. A few examples of these compounds are benzene and toluene.

Classification of Aromatic Compounds

Aromatic compounds have distinctive stability and this is why they are referred to as aromaticity which is majorly concerned with odour. Now we will discuss the classification of these compounds, which are basically Benzenoid Aromatic Compounds and Non-Benzenoid Aromatic compounds. Further, we will discuss them in detail.

1. Benzenoid Aromatic Compounds

These aromatic compounds are mainly obtained from benzene. These compounds are distinguished by the existence of one or more than one isolated or fused benzene rings and their derivatives additionally in the structure. These compounds can be arranged as Monocyclic, Bicyclic and Tricyclic on the basis of the number of benzene rings which are fused together in the structure. In bicyclic and tricyclic compounds, there are two or more than two rings present in the structure. A few examples of these compounds are Phenanthrene, Naphthalene, Anthracene. In addition, a few of such compounds are represented below.

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2. Non-benzenoid Aromatic Compounds

These aromatic compounds consist of other unsaturated rings instead of benzene rings. These aromatic compounds have special stability. Some examples of these compounds are Tropolone and Azulene.

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2. Classification based on the functional groups

A functional group can be defined as a process in which a molecule receives its characteristic chemical properties from one or group of atoms that exist in the molecule. Now we must understand why we need to classify organic compounds on the basis of functional groups. The answer is very simple because it classifies the chemical behaviour of an organic compound. We need to understand that the nature of functional groups draws impacts on the reactions of compounds and at some level, their physical properties.

There are numerous organic reactions, which involve functional group transformation, and have no effect on the rest of the molecules. There are so many examples in the functional group case, such as the carboxylic acid group (-COOH), the hydroxyl group (-OH) and the aldehyde group (-CHO).