entering group

https://doi.org/10.1351/goldbook.E02130
An atom or group that forms a bond to what is considered to be the main part of the @S06082@ during a reaction. For example: the attacking @N04249@ in a @M03989@ nucleophilic @S06078@.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1113 [Terms] [Paper]