有机化学中常见的反应像取代反应（substitution），消去反应（elimination），加成反应（addition），酯化反应（esterification），水解反应（hydrolysis），氧化反应（oxidation），还原反应（reduction），缩合反应（condensation）等等，既多且难区分。
要想理解反应机理，为大家总结16个定义！
1、Functional group
a group of atoms responsible for the characteristic reactions of an organic compound.
2、Homolytic fission
the splitting of a covalent bond where each atom retains one electron from the bonding pair.
3、Heterolytic fission
the splitting of a covalent bond where one atom retains both electrons from the bonding pair.
4、Free radical
an uncharged molecule with an unpaired electron.
5、Initiation
an initial chemical reaction which triggers further reactions.
6、Propagation
a secondary reaction where there is no net gain or loss of free radicals.
7、Termination
the final step in a chain reaction where a reactive intermediate is rendered inactive.
8、Nucleophile
a molecule or substance that donates electrons.
9、Electrophile
a molecule or substance that acts as an electron pair acceptor.
10、Addition
a reaction where two or more molecules react to form a larger molecule.
11、Substitution
a reaction where an atom or group is replaced by another atom or group.
12、Elimination
a reaction in which two substituents are removed from a molecule in a mechanism with one or two steps.
13、Hydrolysis
the splitting up of a compound or molecule using water.
14、Condensation
the formation of a compound with the release of water.
15、Oxidation
the formation of a compound with the release of water.
16、Reduction
gain of electrons.
如果你想了解更多A-level课程，留学规划或者有任何疑问，欢迎联系新航道重庆学校。
新航道重庆学校官网：cq.xhd.cn
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