Organic Chemistry

Classification of Organic Compounds

Organic compounds constitute about 90% of all compounds. That’s quite a lot, isn’t it? In order to study such a vast number of compounds, it is necessary to classify them into categories. Let us know more about the Classification of Organic Compounds as well as the general categories into which organic compounds are divided.

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Classification of Organic Compounds

Depending upon the arrangement of carbon atoms in their structure, organic compounds are broadly categorized into

  • Acyclic or Open Chain compounds
  • Cyclic or Closed Chain compounds

The following diagram will give you a clear idea about the classification of organic compounds:

Classification of Organic Compounds

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The carbon atoms are present in the form of an open chain.This chain may either be a straight chain or a branched chain. These were initially known as Aliphatic compounds because the compounds of this class were derived from either animal or vegetable fats

  • Straight Chain Compounds: The carbon skeleton is in the form of a straight chain. Examples:

n-Propane  CH3-CH2-CH3

Propene      CH2=CH-CH3

  • Branched Chain Compounds: The carbon skeleton is in the form of a branched chain. Examples: IsobutyleneClassification of Organic Compounds

Cyclic or Closed Chain Compounds

They are marked by the presence of one or more closed chains or ring of atoms in their structure. Depending on whether there is a presence of any other atom apart from carbon in the constitution of the ring, they are further classified as:

  • Homocyclic or Carbocyclic Compounds
  • Heterocyclic Compounds

Homocyclic or Carbocyclic Compounds

The rings in these compounds are entirely made up of carbon atoms. No other atom is present in the ring skeleton.These can be further divided into two sub-classes:

  • Alicyclic Compounds
  • Aromatic Compounds

Alicyclic Compounds

Their name is attributed to their resemblance to Aliphatic compounds in their properties. The examples of this category include cyclopropane, cyclobutane, cyclopentane, cyclohexane, etc.

Classification of Organic Compounds

Aromatic Compounds

These are cyclic unsaturated compounds. They derive their name from the Greek word Aroma which means “fragrant smell” since most of these compounds bear a pleasant smell. These are further classified into two types:

  • Benzenoid Aromatic Compounds: They are characterized by the presence of one or more fused or isolated benzene rings as well as their derivatives in their structure. Depending upon the number of benzene rings that are fused together in their structure, they can be further classified as Monocyclic, Bicyclic, Tricyclic.
  • Non-Benzenoid aromatic Compounds: They are characterized by the presence of a single benzene ring to which other groups are attached.

Classification of Organic Compounds

Classification of Organic Compounds


Bicyclic and Tricyclic Compounds

These are characterized by the presence of two or more rings in their structure.Examples include Naphthalene, Phenanthrene as well as Anthracene.

Classification of Organic Compounds


Classification of Organic CompoundsPhenanthrene

Classification of Organic Compounds


Non-Benzenoid Aromatic Compounds

Aromatic compounds that contain other highly unsaturated rings in place of the benzene ring are called non-benzenoid aromatic compounds. Examples include

Classification of Organic Compounds


Classification of Organic Compounds


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Organic Compounds

Heterocyclic Compounds

When one or more heteroatoms such as oxygen, nitrogen, sulphur, boron, silicon etc, are present in the ring such compounds are known as heterocyclic compounds.

  • Alicyclic heterocyclic compounds: Aliphatic heterocyclic compounds that contain one or more heteroatoms in their rings are called alicyclic heterocyclic compounds.

Classification of Organic Compounds

  •  Aromatic heterocyclic compounds Aromatic heterocyclic compounds that contain one or more heteroatoms in their ring skeleton are called aromatic heterocyclic compounds.

Classification of Organic Compounds

Solved Questions For You

Que: Which of these is not an aromatic compound?


Classification of Organic Compounds


Classification of Organic Compounds


Classification of Organic Compounds


Classification of Organic Compounds

Ans: The correct answer is option b. It is the structure of cyclohexane which is an alicyclic compound.

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