Q.The IUPAC name of the following compound is (a chiral carbon bonded to Br, CH3, OH and H)

A carbon bearing four different groups is a stereocentre, and the Cahn-Ingold-Prelog (CIP) rules assign it an unambiguous $R$ or $S$ label based purely on priority: rank the four attached groups by the atomic number of the directly attached atom (breaking ties by comparing what those atoms are in turn attached to, moving outward), orient the molecule with the lowest-priority group pointing away from the viewer, then trace the remaining three groups from highest to lowest priority -- a clockwise path is $R$ (rectus), a counterclockwise path is $S$ (sinister). Because CIP priority depends only on what atoms are actually attached (not on which particular group left or arrived in a reaction), it is possible for a leaving group and an incoming nucleoph …