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:
Browse more Topics under Organic Chemistry
- General Introduction to Organic Compounds
- Isomerism
- Nomenclature of Organic Compounds
- Purification of Organic Compounds
- Qualitative Analysis of Organic Compounds
- Quantitative Analysis of Organic Compounds
- Structural Representations of Organic Compounds
- Types of Organic Reactions
- Fundamental Concepts of Organic Reaction Mechanism
Acyclic or Open Chain Compounds
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: Isobutylene
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.
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.
Aniline
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.
Naphthalene
Phenanthrene
Anthracene
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
Azulene
Tropolone
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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.
- Aromatic heterocyclic compounds Aromatic heterocyclic compounds that contain one or more heteroatoms in their ring skeleton are called aromatic heterocyclic compounds.
Solved Questions For You
Que: Which of these is not an aromatic compound?
a.
b.
c.
d.
Ans: The correct answer is option b. It is the structure of cyclohexane which is an alicyclic compound.
