1. Multiple Bonds, Pi MOs, Delocalization

2. Permanganate Test Results Hexane, C 6 H 14 Hexene, C 6 H 12 Limonene Blank Pinene, C 10 H 16

3. Trigonal Planar Electron Group Geometry Methanal (Formaldehyde) Ethene (Ethylene) 120 o Perfect Trigonal Planar Arrangement

4. Bond Angles Deviate From 120 o Methanal (Formaldehyde)Ethene (Ethylene)

5. Two Models for Ethene

6. Sigma Bonding Orbital Between C Atoms in Ethene

7. Pi Bonding Orbital Formation at C Atoms in Ethene

8. The Double Bond in Ethene sigma orbital for first part of bond pi orbital for second part of bond

9. The Sigma Framework in Ethene

10. The Pi Bond in Ethene

11. The 5 Sigma and 1 Pi Bonding Orbitals in Ethene

12. Isomerism Same number, kind of atoms Different connectivity Non-superimposable mirror images Same connectivity but different spatial arrangement e.g., cis,trans Isomers Structural Isomers Stereoisomers Geometric Isomers Optical Isomers Conformational Isomers Interconvert by sigma bond rotation

13. Cis-Trans Isomerism Trans Cis Interconversion Requires Breaking the Pi Bond

14. Conformational Isomerism Interconversion Requires Only Sigma Bond Rotation Same Molecule, Just Different Rotations 1,2-dichloroethane