Identify each set of equivalent carbon atoms in butane and count the number of equivalent carbon atoms in each set. Do the same for 2-methylpropane. Draw structural formulas for the four isomeric compounds with the molecular formula C_4H_9Br. Name each isomer. How many sets of equivalent carbon atoms are there in each isomer? Draw the structural formulas for the nine isomers with the molecular formula C_4H_8Br_2. Name each isomer.