1.1 Organic chemistry

  General Organic Chemistry

There is no fundamental difference between organic and inorganic compounds. The main reasons for the need of separate branch of organic chemistry are,

1. Number of compounds: There are a large number of organic compounds due to the property of the carbon atoms to combine with one another to form long chains and rings. This property of carbon atoms is called catenation.

2. Composition: Organic compounds are made up of few elements only like carbon, hydrogen, oxygen, halogen, sulphur, phosphorus etc. where as inorganic compounds may contain any two or more than two of various known elements.

3. Complexity of molecules: Although organic compounds are made up of few elements yet many of the organic molecules have complex structure and very high molecular masses.

For example molecules of proteins are made up of thousands of atoms.

4. Types of linkages: Organic compounds generally contain covalent linkages in their molecules while inorganic compounds are generally ionic in nature.

5. Stability: The organic compounds are relatively less stable than inorganic compounds. The organic compounds usually decompose on heating. For some compounds, the decomposition starts even below the room temperature.

6. Isomerism: Organic molecules are capable of exhibiting the phenomenon of isomerism. Isomerism is the phenomenon by virtue of which two or more compounds have different properties but same molecular formula.

For example: The formula $C_2H_6O$ represents two compounds $CH_3OCH_3$ and $C_2H_5OH$ having different properties.

7. Melting and boiling points: Organic compounds usually have low melting and boiling points because of their covalent nature. Inorganic compounds usually have high melting and boiling points.

8. Nature of reactions: Organic reactions are generally complicated and slow. They involve breaking of old bonds in reacting molecules and formation of new bonds in product molecules. Inorganic reactions, on the other hand, are generally ionic.

9. Origin: Organic compounds are mostly obtained from the living sources: animals or plants. Inorganic compounds, on the other hand, find their origin from minerals.

10. Combustibility: Organic compounds are combustible. Inorganic compounds are generally non-combustible.

Reasons for the existence of such a large number of organic compounds

The number of organic compounds is more than 5 million. The existence of such a large number of organic compounds is due to the following properties of carbon.

1. Catenation: The property of atoms of an element to link with one another forming chain of identical atoms is called catenation.

Carbon exhibits catenation to maximum extent because of strong carbon-carbon bond and tetra covalency. Due to the property of catenation carbon atoms can form a various type of straight chain, branched chain and ring structures. Thus giving rise to a large variety of compounds.

2. Isomerism: It is defined as the different compounds having same molecular formula are called isomers and the phenomenon is called isomerism.

The organic compounds exhibit isomerism i.e. for a particular molecular formula two or more different organic compounds may be possible.

3. Formation of multiple bonds: Due to the small size of carbon atom, it is capable of forming multiple bonds with other carbon atoms. This further give rise to a large variety of compounds. Some examples are given as under: