CH3 CH3 CH3 H Br HBr H Br Br H HO H Br -H H -Br CH3 CH3 CH3 CH3 CH3 H Br HBr H Br H OH H Br CH3 CH3 (d) ↓H CH3 CH3 CH3 BI 81 Br Br H H H H& H20 Br CH3 H20 CH3 CH3 CH3 BrCH3 OH CH3 H H Br CH3 CH3 Br Br H H HBr HO CH3 CH3 H Br H HBr CH3 CH3 Br Br H H CH3 CH3 Br Br H H + CH3 CH3 H H Br H2O+ H2O CH3 CH3 Br H H + H+ CH3 CH3 Br Br H H CH3 CH3 Br Br H H + （dl）