Abstract Electronic effect and conjugative effect are the key factors in organic reactions. The aspect of alternating polarity in the conjugative system is very obvious in the reactions such as 1,2-addition and 1,4-addition of conjugative alkadiene or α,β-unsaturated aldehyde and ketone, electrophilie substitution of benzene direvatives. Mastering the characteristics of alternating polarity in the conjugative system can get twice the result with half the effort in studying these reactions mentioned above.
