Structure and Bonding in
Organic Chemistry
Electron Configurations
Lewis Dot Structures
Hybridization
Orbital 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 (s) Bond
Wave Depiction of H2
Molecular Orbitals
Mathematical Combination of Atomic Orbitals
Antibonding Molecular Orbital
Destructive Overlap Creates Node
s and s* 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
carbon - 4 valence e
hydrogen - 1 valence e
.
.C.
.
H.
1s22s22p2
1s
All Have the Same Geometry
All Have 4 Regions of Electron Density
Tetrahderal Geometry
Methane Representations
In Ground State
2 bonding sites, 1 lone pair
H
CH4
2p
C
H
H
H
2s
x
y
z
ground state
3
sp
Hybridization
4 Regions of electron Density
link
H
CH 4
2p
C
H
2s
H
H
x
y
z
ground state
hybridize
2p
2s
x
y
z
excited state
4 identical sp 3 orbitals
4 sigma bonds requires 4 hybrid orbitals
tetrahedral geometry
4
sp3
Hybridization of 1 s and 3 p
Orbitals – sp3
sp3 is Tetrahedral Geometry
Methane
Ammonia
Tetrahedral Geometry
Pyramidal Shape
Orbital Depiction of Ethane,
C2H6 , the s bond
Depictions of 2-Methylbutane
Bonding Characteristics of Period 2
Elements
“Saturated” with Hydrogen
A Model of a Saturated Hydrocarbon
sp2 Hybridization
3 Regions of Electron Density
CH 2=CH 2
H
2p
H
C
2s
C
H
x
H
hybridize
2p
2s
x
y
z
excited state
y
z
ground state
pz
3 identical sp 2 orbitals
3 sigma bonds requires 3 hybrid orbitals
trigonal planar geometry
3
sp2 pz
Hybridization of 1 s and 2 p
Orbitals – sp2
An
2
sp
Hybridized Atom
The p bond
Overlap of 2 parallel p Orbitals
Ethylene CH2=CH2
Views of Ethylene, C2H4
Ethylene
Formaldehyde
sp Hybridization
2 Regions of Electron Density
H
C
2p
C H
x
2s
y
z
ground state
hybridize
2p
2s
x
y
z
excited state
py
pz
2 identical sp orbitals
2 sigma bonds requires 2 hybrid orbitals
linear geometry
2
The sp Orbital
Acetylene, C2H2,
1 s bond
2 perpendicular p bonds
Drawing Structures
H
H
H
C
H
H
H
C
H
C
H
H
C
H
Butane, C 4H10
CH3CH2CH2CH3
H
H
H
H C C C
H
H
H
C
H
H
H
Methylpropane, C 4H10
CH3CH(CH3)CH3
Octane Representations
C8H18 is molecular formula but there are 18 possible structural isomers
H
H H H H H H
H
C
C
C
C
H
C
C
C
C
H
H H H HH H
HH
Lewis structure
CH3CH2CH2CH2CH2CH2CH2CH3
CH3(CH2)6CH3
condensed structural formula
Condensed
Formulas
Line-Angle Structures are
Often Used as a Short-hand
H
H H H H H H
H
C
C
C
C
H
C
C
C
C
H
H H H HH H
HH
Lewis structure
Line-angle or "zig-zag" structures
Line-Angle Structures
C12H26
H
H
H
H
H
C
H
H
H
C
H H
C
C
H
H
H
H
C
C
H
H
H
H
H
C
C
H
H
H
H
H
C
H
C
H
C
H
H
H
C
H
H
H
H
H
H H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
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.
H
H
H
H
H
H
H
H
H H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Line-Angle structure
Superimposed on Lewis Structure
H
H
H
C
H
H
H
C
H H
C
C
H
H
H
H
C
H
C
H
H
C
C
H
H
H
H
C
H
C
H
C
H
H
C
H
H
H
Double Bonds are Shown
Depictions of trans 2-pentene
H
H
H
C
C
H
H
H
C
C H
H
C
H H
Lewis Structure
CH3
H
C
C
H
CH2CH3
condensed structural formula
line-angle or zig-zag structure
For Cyclic Structures, Draw the
Corresponding Polygon
Cyclohexane
H H
H
H
C
C H
H C
H C
C H
C
H
H
H
H
Drawing Clear Structures
Structures take Cues from Models
Some Steroids
OH
O
HO
Cholesterol
C27H44O
Testosterone
C19H26O2
Benzene can be drawn as one of
two resonance structures
H
H
H
C
C
C
C
H
H
C
C
H
H
H
H
C
C
C
C
H
C
C
H
H
Some Line-Angle Structures