2.亲电加成反应( Electrophilic Addition): C=C +Y-Z Y Z Mechanism R H R H A C-C-H R R H R H R B C-C-H R R H2. 亲电加成反应(Electrophilic Addition) ： - C = C- + Y - Z - C - C - Y Z Mechanism: C C H H R R Y Z C C H H H R R + C C H H H R R + Z - C C H H H R R Z A: B: