应用取代法推断有机物分子的同分异构体时,首先要确定被取代的分子中氢原子的种数,通常有几种位置不同的氢原子,则会有几种相应的取代产物。在被取代的分子中,处于分子对称位置上的氢原子或按系统命名位置等同的碳原子上的氢原子即为等效氢。同一取代基不能重复取代等效氢。在同种取代基进行多元取代时,首先要确定一元取代物有几种,然后在这几种一元取代物上进行二元取代。对第一种一元取代物进行二元取代时,只需注意不取代等效氢。但对第二种一元取代物进行二元取代时,不仅不能取代等效氢,而且还不能 When using substitution method to infer the isomers of organic molecules, we must first determine the number of hydrogen atoms in the substituted molecules. Usually there are several hydrogen atoms in different positions, and there will be several corresponding substitution products. In a substituted molecule, a hydrogen atom at the symmetric position of the molecule or a hydrogen atom on a carbon atom that is equivalent in position to the system is equivalent hydrogen. The same substituent cannot replace the equivalent hydrogen repeatedly. When multiple substitutions of the same kind of substituents are performed, it is first necessary to determine several kinds of monovalent substitutions, and then perform binary substitutions on these kinds of monovalent substitutions. When binary substitutions are made for the first one-membered metabolites, it is only necessary to take care not to replace the equivalent hydrogen. However, when the binary substitution of the second one-membered substitution is performed, it cannot only replace the equivalent hydrogen, but it cannot