$\begin {array} {1 1} (1)\;BrCH_2-CH_2-CH_2-CH_2Br & \quad (2)\;H_3C-CH-CH_2-CH_3 \\ (3)\;H_3C-Ch_2-CH_2-CH_2Br & \quad (4)\;H_3C-CH_2-CBr_2-CH_3 \end {array}$