12.试写出下列各反应生成的一卤代烷,预测所得异构体的比例。-|||-(1) (H)_(3)C(H)_(2)C(H)_(3)+(Cl)_(2)xrightarrow [高温](hv)-|||-(2)(CH3)3 CCH(CH3)2室温,CCl4-|||-CH3-|||-(3) _(3)C-C-Hdfrac ({Br)_(2),(h)_(2)}(UND),C(Cl)_(4)-|||-CH3