MO Energy Diagram CE butadiene ethylen The average energy of electrons is antibonding energy of bonding isolated lower in the o or conJugated compound > Chaper 15
Chaper 15 11 MO Energy Diagram The average energy of electrons is lower in the conjugated compound. =>
Conformations of H 1.3-Butadiene s-trans conformer is more stable than the s-cis by 2.3 kcal Easily interconvert at room temperature H H H H H H H S-trans H Chaper 15 12
Chaper 15 12 Conformations of 1,3-Butadiene • s-trans conformer is more stable than the s-cis by 2.3 kcal. • Easily interconvert at room temperature. H H H H H H s-trans s-cis H H H H H H =>
H H H Allylic Cations Carbon adjacent to C=C is allylic Allylic cation is stabilized by resonance Stability of1° allylic≈2° carbocation. Stability of2° allylic≈3° carbocation H H,C=C-CH, H2C一C=CH2 Chaper 15 13
Chaper 15 13 Allylic Cations • Carbon adjacent to C=C is allylic. • Allylic cation is stabilized by resonance. • Stability of 1 allylic 2 carbocation. • Stability of 2 allylic 3 carbocation. H2 C C H CH2 + H2 C C H CH2 + =>