Structure and Bonding in Organic Chemistry Electron Configurations Lewis Dot Structures...

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 (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

zyx2p

2sH

HH

H

CCH4

sp3 Hybridization 4 Regions of electron Density link

4

tetrahedral geometryexcited state

hybridize

4 identical sp3 orbitalszyx2p

2s4 sigma bonds requires 4 hybrid orbitals

CH4C

H

HH

H 2s

2p 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

2s

2p x y z

ground state

2s

2p x y z3 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

2s

2p x y z

ground state

2s

2p x y z2 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

C

CH3

H

C

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

HHH

H

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