1. Structural Isomers
Compounds that have the same molecular formula, but different structural formula (arrangement of atoms), are called structural isomers
have different properties, such as b.p., m.p., and reactivity

2. Examples of Isomers CH3 The formula C4H10 has two different structures
CH3CH2CH2CH3 CH3CHCH3
Butane methylpropane
When a CH3 is is used to form a branch, it makes a new isomer of C4H10.

3. Learning Check
Write the structural formulas of 3 isomers that have the formula C5H12. Name each.

4. Solution CH3CH2CH2CH2CH3 pentane CH3CHCH2CH3 2-methylbutane
CH3CCH3 2,2-dimethylpropane