-Disubstituted:trans more stable than cis steric repulsion ethylene, unsubstituted 2.7 kcal (11kJ) monosubstituted R 4.2 kcal H (18kJ) K8Jeua 4.8 kcal cis (20kJ) 5.2 kcal R (22kJ) =0 H 5.9 kcal disubstituted geminal trans (25kD 6.2 kcal c=c R (26kJ) C=c R trisubstituted c=c R、 tetrasubstituted R H R、 CR R R Disubstituted: trans more stable than cis steric repulsion C C H H H H H H H H C C H H H H H H H H Relative Stabilities