Multiple Bonds, Pi MOs, Delocalization

Permanganate Test Results

Hexane, C6H14

Hexene, C6H12

Limonene

BlankPinene, C10H16

Trigonal Planar Electron Group Geometry

Methanal (Formaldehyde)

Ethene

(Ethylene)

120o

Perfect Trigonal Planar Arrangement

Bond Angles Deviate From 120o

Methanal (Formaldehyde)Ethene (Ethylene)

Two Models for Ethene

Sigma Bonding Orbital Between C Atoms in Ethene

Pi Bonding Orbital Formation at C Atoms in Ethene

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

The Double Bond in Ethene

sigma orbitalfor first part

of bond

pi orbitalfor second

part of bond

The Sigma Framework in Ethene

The Pi Bond in Ethene

The 5 Sigma and 1 Pi Bonding Orbitals in Ethene

IsomerismSame 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

Cis-Trans Isomerism

Trans Cis

Interconversion Requires Breaking the Pi Bond

Conformational Isomerism

Interconversion Requires Only Sigma Bond Rotation

Same Molecule, Just Different Rotations

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

1,2-dichloroethane