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