This action assigns map numbers to the corresponding atoms on the two sides of the reaction arrow.
Options:

• Select the mapping style as Complete, Matching, or Changing.

• "Map reaction" can also Mark bonds that have changed in the reaction.

• Keep existing mapping (on by default)

Note : Reactions are mapped by the AutoMapper tool.
Action "mapreaction" considers only reactions; molecules or multiple fragments are not mapped.

Example :