What is isomerism?

Isomerism is the phenomenon where two or more different compounds have the same molecular formula but different arrangements of atoms (different structures or spatial arrangements), leading to different physical and chemical properties.

Example:

Ethanol and dimethyl ether both have molecular formula $\mathrm{C_2H_6O}$.

Ethanol: $\mathrm{CH_3-CH_2-OH}$

Dimethyl ether: $\mathrm{CH_3-O-CH_3}$

Types of Isomerism:

1. Structural (Constitutional) Isomerism: Same molecular formula, different connectivity of atoms.

2. Stereoisomerism: Same connectivity, different spatial arrangement.

   • Geometrical (cis-trans)
   • Optical (enantiomers)

Isomerism is the existence of two or more compounds with the same molecular formula but different structures.