Isomers are compounds which have the same molecular formula. Constitutional isomers have different connectivity; the atoms are connected in different ways.
1. (CH₃)₃COCH₃
2. (CH₃)₂CHOCH3₃
3. (CH₃)₂CHOCH₂CH₃
Molecules 1 and 3 have the same formula (C₅H₁₂O) and are isomers. Molecule 2 is not an isomer. From the structural formula, it is clear that Molecules 1 and 3 have different connectivity.
