Classification of Organic Compounds

Science > Chemistry > Introduction to Organic Chemistry > Classification of Organic Compounds

In the last artivle we have studied what is organic chemistry? Why it is termed as chemistry of carbon compounds nowaday? In this article we shall study classification of organic compounds. Depending upon the structure organic compounds are classified into two types. viz. open-chain organic compounds or aliphatic organic compounds or Acyclic organic compounds and closed chain organic compounds or cyclic organic compounds

Open Chain Organic Compounds:

Open chain organic compounds are organic compounds that contain an open chain of carbon atoms which may be straight-chain or branched-chain.

Closed Chain Organic Compounds:

Closed chain organic compounds are organic compounds that contain one or more closed chains or rings of carbon atoms. Closed chain organic compounds are further classified into two types. viz. homocyclic organic compounds or carbocyclic organic compounds. and heterocyclic organic compounds

Homocyclic Carbon Compounds: 

Homocyclic organic compounds are organic compounds that contain one or more closed rings of carbon atoms only. Homocyclic organic compounds are further classified into two types. viz. alicyclic organic compounds and aromatic organic compounds

Alicyclic Organic Compounds: 

Alicyclic organic compounds are homocyclic organic compounds that have properties similar to that of aliphatic compounds.

Aromatic Organic Compounds:

Aromatic organic compounds are homocyclic organic compounds that contain at least one benzene ring.

Heterocyclic Organic Compounds: 

Heterocyclic organic compounds are organic compounds that contain at least one atom other than a carbon atom in the ring.

Homologous Series:

A series of organic compounds which have a common general formula and in which the two successive members of the series differ by – CH₂ – is known as homologous series. The individual member of the homologous series is called homologue.

Alkane Series:

Sr. No.	Alkane	Molecular Formula	Difference with last alkane	Molecular mass	Difference w.r.t. last alkane
1	Methane	CH4	–	16	–
2	Ethane	C2H6	– CH2 –	30	14
3	Propane	C3H8	– CH2 –	44	14
4	Butane	C4H10	– CH2 –	58	14

Alcohol Series:

Sr. No.	Alcohol	Molecular Formula	Difference with last alcohol	Molecular mass	Difference w.r.t. last alcohol
1	Mehanol	CH3OH	–	32	–
2	Ethanol	C2H5OH	– CH2 –	46	14
3	Propanol	C3H7OH	– CH2 –	60	14
4	Butanol	C4H9OH	– CH2 –	74	14

Characteristics of Homologous Series:

• Members of the same homologous series are represented by the same general formula. E.g. all alkanes are represented by the same general formula C_nH_{2n + 2}.
• They can be prepared by similar methods of preparation.
• They have the same functional group hence have a number of chemical properties in common which are called the general properties.
• They show a regular gradation in physical properties such as melting and boiling points.
• Each member of the homologous series is known as the homologue of the other elements and differs from its next higher or next lower homologue by a common difference –CH₂–
• Each member of the homologous series differs from its next higher or next lower homologue in molecular weight by 14.

Science > Chemistry > Introduction to Organic Chemistry > Classification of Organic Compounds