Chains, Branches and Rings

Saturated and Unsaturated Hydrocarbons

Saturated hydrocarbons: These hydrocarbons have all carbon-carbon single bonds. These are known as alkanes. General formula = C_nH_2n+2 where n = 1, 2, 3, 4.…..
Unsaturated hydrocarbons: These hydrocarbons have at least one carbon-carbon double or triple bond.
Hydrocarbons with at least one carbon-carbon double bond are called alkenes. General formula = C_nH₂n where n = 2, 3, 4…..
Hydrocarbons with at least one carbon-carbon triple bond are called alkynes. General formula = C_nH_2n−2 where n = 2, 3, 4…..

Chains, Rings and Branches

Carbon chains may be in the form of straight chains, branched chains or rings.

In cyclic compounds, atoms are connected to form a ring.

Structural Isomers

The compounds with the same molecular formula and different physical or chemical properties are known as isomers and the phenomenon is known as isomerism.
The isomers that differ in the structural arrangement of atoms in their molecules are called structural isomers and the phenomenon is known as structural isomerism.

Benzene

Benzene is the simplest organic, aromatic hydrocarbon.
Physical properties: colourless liquid, pungent odour, flammable, volatile.
Structure:
Cyclic in nature with chemical formula, C₆H₆, i.e., each carbon atom in benzene is arranged in a six-membered ring and is bonded to only one hydrogen atom.
It includes 3-double bonds which are separated by a single bond.
Hence, this arrangement is recognized to have conjugated double bonds and two stable resonance structures exist for the ring.