At 0C 1.2-addition is favored H H HH Br H H Br H+HBr H H H H H H H H H H H 1,3-Butadiene 3-Bromo-1-butene 1-Bromo-2-butene (a conjugated diene) (71%;1,2 addition) (29%;1,4 addition) e2004 Thomson-Brooks/Cole At 0oC 1,2-addition is favored