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Classification of organic compounds

There are millions of organic compounds and this makes it physically impossible to study each individual compound. To facilitate their study, organic compounds are classified into various groups and sub-groups.

They may be broadly classified into the following classes:

* Open chain or acyclic compounds.

* Closed chain or cyclic (or ring) compounds.

These compounds contain an open chain system of carbon atoms. The chains may be either straight chains (non-branched) or branched. The open chain compounds are also called aliphatic compounds. The name aliphatic is derived from the Greek word aleiphar meaning fats, as the earlier known compounds of this class were either obtained from animal or vegetable fats, or had fat like character.

Straight chain (or non-branched) compounds

CH3-CH2-CH2-CH3 CH3-CH2-CH2-CH2OH H2C = CH2

Butane 1- butanol ethene

Branched chain compounds

These compounds contain one or more closed chains (rings) of atoms and are known as cyclic or ring compounds.

These are of two types:

* Homocyclic compounds, or carbocyclic compounds

* Heterocyclic compounds.

Homocyclic or Carbocyclic compounds

The compounds in which the ring consists of only carbon atoms are called homocyclic or carbocyclic compounds. Homocyclic compounds or carbocylic compounds are further divided into:

(a) Alicyclic compounds (b) Aromatic compounds

Alicyclic compounds

When a ring of three or more carbon atoms resembling aliphatic compounds are contained in homocyclic or carbocyclic compounds, they are called alicyclic compounds. The saturated alicyclic hydrocarbons have the general formula CnH2n. Typical alicyclic compounds are given below.

cyclopropane cyclobutane cyclohexane

cyclopropene cyclohexene cyclohexa-1,4-diene cyclopentene

Aromatic compounds

These carbocylic compounds contain at east one benzene ring i.e., a ring of six carbons atoms with alternate double and single bonds. Aromatic compounds are...