Predict the number of constitutional isomers that can form when butane reacts with chlorine, according to the equation given. Draw the structural formula(s) for the possible isomer(s). \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}+\mathbf{C l}_{2} \longrightarrow

\mathbf{C}_{4} \mathbf{H}_{9} \mathbf{C l}+\mathbf{H C l}