Structure and Bonding in Organic Chemistry

Electron ConfigurationsLewis Dot Structures

HybridizationOrbital depictions

Organic Chemist’s Periodic Table

Molecular Model of Aspirin

Nucleus is a Tiny Fraction of the Volume of an Atom

Orbitals are Probabilities

2s Orbital Has a Node

Bonding in H2

Sigma (Bond

Wave Depiction of H2

Molecular OrbitalsMathematical Combination of Atomic Orbitals

Antibonding Molecular Orbital Destructive Overlap Creates Node

and * of H2

Energy Released When Bond Forms

Electron Configurations

Ground State Electron Configurations

The p Orbital

px, py, pz

Electron Configuration of Carbon

Lewis Dot Structure of Methane

C... .

carbon - 4 valence e hydrogen - 1 valence e

H.

1s22s22p2 1s

All Have the Same GeometryAll Have 4 Regions of Electron Density

Tetrahderal Geometry

Methane Representations

In Ground State2 bonding sites, 1 lone pair

ground state

zyx2p2sH

HH

H

CCH4

sp3 Hybridization 4 Regions of electron Density link

4

tetrahedral geometryexcited state

hybridize

4 identical sp3 orbitalszyx2p2s

4 sigma bonds requires 4 hybrid orbitals

CH4 C

H

HH

H 2s2p x y z

ground state

sp3

Hybridization of 1 s and 3 p Orbitals – sp3

sp3 is Tetrahedral GeometryMethane

Ammonia Tetrahedral Geometry

Pyramidal Shape

Orbital Depiction of Ethane, C2H6 , the bond

Depictions of 2-Methylbutane

Bonding Characteristics of Period 2 Elements

“Saturated” with Hydrogen

A Model of a Saturated Hydrocarbon

sp2 Hybridization3 Regions of Electron Density

pz

H

HC

H

H

CH2=CH2

C

3 sigma bonds requires 3 hybrid orbitals

2s2p x y z

ground state

2s2p x y z 3 identical sp2 orbitals

hybridize

excited statetrigonal planar geometry

3sp2 pz

Hybridization of 1 s and 2 p Orbitals – sp2

An sp2 Hybridized Atom

The bondOverlap of 2 parallel p Orbitals

Ethylene CH2=CH2

Views of Ethylene, C2H4

Ethylene

Formaldehyde

sp Hybridization2 Regions of Electron Density

py

H C HC

pz

2 sigma bonds requires 2 hybrid orbitals

2s2p x y z

ground state

2s2p x y z 2 identical sp orbitals

hybridize

excited statelinear geometry

2

The sp Orbital

Acetylene, C2H2, 1 bond

2 perpendicular bonds

Drawing Structures

CC

CC

H

H

H

H

HH H

HH

H

Butane, C4H10

CC

C

C

H

H H

HH

H H

HHH

Methylpropane, C4H10

CH3CH2CH2CH3 CH3CH(CH3)CH3

Octane Representations

CC

CC

CC

CC

H

HH

H H

H H

H H

H H

H H

HHH

HH

CH3CH2CH2CH2CH2CH2CH2CH3

CH3(CH2)6CH3

Lewis structure condensed structural formula

C8H18 is molecular formula but there are 18 possible structural isomers

Condensed Formulas

Line-Angle Structures are Often Used as a Short-hand

Line-angle or "zig-zag" structures

Lewis structure

CC

CC

CC

CC

H

HH

H H

H H

H H

H H

H H

HHH

HH

Line-Angle Structures

CC

CC

CC

C

CC

C

CC

HH

H

H

H

H

H HH

H H

H

H

H

H

H

HH

HH

H

H H

HH

H

HH

H

H

H

H

H HH

H H

H

H

H

H

H

HH

HH

H

H H

HH

H

C12H26

HH

H

H

H

H

H HH

H H

H

H

H

H

H

HH

HH

H

H H

HH

H

At the end of every line and at the intersection of any lines there is a carbon atom with 4 bonds. Hydrogen atoms

are mentally supplied to fill the valency to 4.

Line-Angle structure Superimposed on Lewis Structure

CC

CC

CC

C

CC

C

CC

HH

H

H

H

H

H HH

H H

H

H

H

H

H

HH

HH

H

H H

HH

H

Double Bonds are Shown

Depictions of trans 2-pentene

C C

H

CC

H H

H

HH

C

H

HH

H

Lewis Structure

CCH3

HC

H

CH2CH3

condensed structural formula

line-angle or zig-zag structure

For Cyclic Structures, Draw the Corresponding Polygon

Cyclohexane

CC

CC

C

C

HHH

HH

HHHH

HH

H

Drawing Clear Structures

Structures take Cues from Models

Some Steroids

HOCholesterol

C27H44O

OH

OTestosterone

C19H26O2

Benzene can be drawn as one of two resonance structures

CC

CC

C

C

H

H

H

H

H

H

CC

CC

C

C

H

H

H

H

H

H

Some Line-Angle Structures