pro-R, pro-S

https://doi.org/10.1351/goldbook.P04889
A @[email protected] group c (as in tetrahedral Xabc2) is described as pro-R if, when it is arbitrarily assigned @[email protected] over the other @[email protected] group c, the configuration of the thus generated @[email protected] centre is assigned the @[email protected] R. The other group c is then described as pro-S. This method for distinguishing between @[email protected] groups can be applied to other kinds of prochiral molecular entities or @[email protected] parts of molecular entities considered on their own.
See:
prochirality centre
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2214 [Terms] [Paper]