SCH4U - Introduction to
Organic Chemistry
*S*T*A*R*R*I*N*G*
The ALKANES
The ALKENES
The ALKYL Groups
The Aromatic Compounds
And all Their Little ISOMERS !
1
And Co-Starring
*S T R U C T U R E S*
and
Formulas
With special mention to
The International Union of Pure and
Applied Chemistry
2
Structural Features of
Carbon Compounds
•
•
•
•
The compound may be open-chained or cyclic.
Chains may be straight or branched.
May be saturated or unsaturated.
Rings can be carbocyclic or heterocyclic.
•
You will be dealing with ALL these cases at one time
or another in this class!
3
Structures and Chemical Formulas
• Molecular formulas are only useful for the very simplest
compounds such as CH4 or C2H6, since they give no
information on how atoms connect.
• There is usually more than one way to arrange the
atoms listed in the molecular formula
• Expanded molecular formulas show atoms in the order
that they appear, with brackets to indicate groups
attached to chains.
–ie) CH3C(CH3)2CH2CH3
4
More ways to represent...
Organic compounds can be very
complex!
• A system is needed that shows structure.
Skeleton structures
Expanded structures (full structural formulas)
Condensed structural formulas
Line representations
Skeleton Structures
• Skeleton structure or skeleton formula
•
•
•
Leaves out the hydrogen atoms.
For hydrocarbons, only the carbon skeleton and connecting bonds are
shown.
Bonds are represented as lines.
.
•
– Example: Isobutane
C
C-C-C
6
Expanded Structural
Formulas
• Expanded structural formula
•
•
Shows all atoms with bonds.
Bonds are represented as lines
– Example Isobutane
• Also called a full structural formula.
7
Condensed Formulas
• Condensed formula
•
•
•
Shorthand way of writing formula.
Lists all atoms in order and tells how they are bound together.
C-H bonds are assumed, not shown
– Example: Isobutane
8
Line Structural Diagrams
• Line formula or line representation
•
•
•
•
The end of each line or meeting point represents a carbon atom
Hydrogen not shown, assumed
Zig zag pattern for single and double bonds, triple bonds are in
straight line
Example: Isobutane
9
Isomers
• Structural Isomers: Compounds with the same
number of atoms and bonds but with different
arrangements.
– CH3CH2CH2CH2CH3 CH3CH(CH3)CH2CH3
10
(CH3)4C
Geometric Isomers
Compounds which have the SAME
molecular formula, but different
arrangements of atoms around a double
carbon-carbon bond
• These exist when two or more arrangements are possible due
to the type of bond.
• Alkanes - can rotate about all bonds
–
no geometric isomers
• Alkenes - rigid bond
–
can have geometric isomers
• Alkynes - rigid bond but linear
–
no geometric isomers
Geometric Isomers
(continued)
There are two possible arrangements
Example
H3C
H
C=C
2-butene
CH3
H3C
H
H
cis
Two methyl groups are
on the same side (and
so are the two H’s.
12
H
C=C
CH3
trans
Two methyl groups
are on opposite
sides.