CLASSIFICATION AND NOMENCLATURE
1. KEKULE’S PRINCIPLE
  • Carbon has four valencies.
  • Carbon has a property of catenation. It can make a large chain with addition of other carbons.
  • A carbon atom can share 2, 4 or 6 electrons with other carbons & can form single, double or triple bond.
  • For a carbon atom, it is not possible to make more than 3 bonds with adjacent carbon atom because a carbon atom complete its octet from overlapping which consists directional property.

2. THE FOUR VALENCIES OF CARBON ATOM CAN BE REPRESENTED BY FOLLOWING WAY



3. CLASSIFICATION OF CARBON

There are four types of carbon present in organic compounds. The carbon which is directly attached with one, two, three and four carbon atoms are known as primary, secondary, tertiary and quarternary carbon atom respectively. On the basis of carbon atom, hydrogen atoms bonded with 1º, 2º or 3º are named as primary, secondary or tertiary hydrogen atom respectively.


4. CLASSIFICATION OF ORGANIC COMPOUNDS:


IMPORTANT POINTS :

 Saturated compounds having carbon-carbon single bonds.
e.g. CH4, CH3–CH3, CH3–CH2–CH3

 Unsaturated compounds having atleast one carbon-carbon multiple bond (= or =)

e.g.

 
Homocyclic compounds having similar types of atoms in the complete cycle. Whereas heterocyclic compounds having atleast one different atom (O, S, N) in the cycle.

Alicyclic = Aliphatic + homo/hetero cyclic
                         ?
                 (Alipher = Fats)




Aromatic compounds having sweet smell (aroma), cyclic resonance and follow Huckle's rule (4n + 2 = p electrons) e.g. Benzenoid compounds :





5. HOMOLOGOUS SERIES

The organic compounds which are structural ly similar having same functional groups, combinedly gives a series known as homologous series and the members as homologues.
The homologous series is characterised by :

(i) The two adjacent members are differ by a – CH2 – group or 14 atomic mass unit.

(ii) All the members of a series have same general formula, general methods of preparation and similar chemical properties due to same functional group.

(iii) The homologues shows difference in physical properties due to change in molecular mass and structural arrangement of molecule.



6. NOMENCLATURE OF ORGANIC COMPOUNDS


Mainly three system are adopted for naming of an organic compound :

(a) Common Name or Trivial Name System
(b) Derived Name System
(c) IUPAC Name or Jeneva Name System

COMMON NAMES