Following the completion of organic reaction，the next task is to deal with the reaction mixture. To fulfil this work, the first thing is to choose a suitable quencher. It is crucial to the success of the experiment. This article mainly discusses how to choose various quenchers for different reactions.

The elements of teaching and the structure of system is the fundamental subject of the teaching theory .Based on the new realization of teaching procedure essence and teaching system elemenu, the article describes that the instruction procedure in chemistry teaching situation involves six elemenu, including instructors, students, text, experiments and teaching environment and teaching theory，constructs the concise chemistry teaching system model.It also explains the theortical significance in theory and practical value of the system.