butane and isobutane are structural isomers. Isobutane is produced by the isomerization reaction of butane. CH3CH2CH2CH3--(t°,AlCl3)-›CH3CH(CH3)-CH3. They have the same chemical formula C4H10.But structural formulas are different Butane CH3CH2CH2CH3 Isobutane CH3CH(CH3)CH3 Isobutane has methyl radical.
