Revised Cahn-Ingold-Prelog (CIP) 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=lk or S,S=lk precedes unlike pair R,S=ul or S,R=ul; and M,M=lk or P,P=lk precedes M,P=ul or P,M=ul; and R,M=lk or S,P=lk precedes R,P=ul or S,M=ul; and M,R=lk and P,S=lk precedes M,S=ul or P,R=ul; also, r precedes s |
| 5 | R precedes S; and M precedes P |