Revised Cahn-Ingold-Prelog Rules - 1982

The lower numbered rule precedes the higher.

Rule Description
0 Nearer end of axis or side of plane precedes farther. Applied to even numbered cumulenes (allenes) and biphenyls with restricted rotation.
1 Higher atomic number precedes lower. Br > Cl > O > N > C > H
2 Higher atomic mass precedes lower. D > H; 81Br > 79Br
3 Seqcis precedes Seqtrans. Z precedes E
4 Like pair R,R or S,S precedes unlike pair R,S or S,R; and M,M or P,P precedes M,P or P,M; and R,M or S,P precedes R,P or S,M; and M,R and P,S precedes M,S or P,R; also, r precedes s
5 R precedes S; and M precedes P