Structure and Bonding in Organic Chemistry - La Salle …price/Structure and Bon… · PPT file ·...
Transcript of Structure and Bonding in Organic Chemistry - La Salle …price/Structure and Bon… · PPT file ·...
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