reference atom

in organic reaction mechanisms
https://doi.org/10.1351/goldbook.R05227
The atom to which a @[email protected] is nucleophilic, electrophilic, nucleofugal or homolytic.
Source:
PAC, 1989, 61, 23. (System for symbolic representation of reaction mechanisms (Recommendations 1988)) on page 55 [Terms] [Paper]