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Organic Chemistry
Introduction
Alkanes
to Organic Chemistry
What is Organic Chemistry?
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What do you think of when you hear
the word organic?
Inorganic?
Organic Chemistry is the study of
carbon containing compounds
Inorganic Chemistry is the study of the
rest of the elements
What is Organic Chemistry?
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Historically, organic compounds were
obtained naturally from plants and
animals
We now have found ways of
synthesizing these organic compounds
(with the desirable properties of the
natural compounds)
Why is Carbon so Special?
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The unique characteristics of carbon
allow for large number of organic
compounds
Carbon forms a total of four covalent
bonds
Thus it can bond to itself or many
different atoms
Forms single, double or triple bonds
Representing Structures

There are a number of different ways
to draw our compounds
Structural Formula
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Shows all the atoms in a structure and
how they are bonded to one another
Are 2-D drawings of 3-D objects thus
they are not totally accurate
“—” A single line represents one pair of
electrons (a single bond)
“=” A double line represents two pairs
of electrons (a double bond)
“≡” A triple line represents three pairs
of electrons (a triple bond)
Condensed Structural
Formula
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Shows the kind and number of atoms
present
Only shows bonds between carbon
atoms
The bond between hydrogen and
carbon is assumed to be present
Expanded Molecular
Formula
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Shows the kind and number of atom
present in the compound
Does not show the actual bonds that
occur, however they are assumed to
be present
When written as a molecular formula,
the above example becomes C3H8
Skeletal Formula
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The end of each line, and the points
where lines meet, represent carbon
atoms
Hydrogen atoms are assumed to be
present in the correct number
You may see this in some books and
online etc but we will not focus on
this!
Terms
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Saturated: organic compounds in
which each carbon atom is bonded to
the maximum number of hydrogen
atoms, thus containing only single bonds
Unsaturated:
organic compounds in
which the carbon atoms do not have the
maximum number of hydrogen atoms
and thus have double or triple bonds
Terms
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Hydrocarbons: organic compounds
consisting of only carbon and hydrogen
– Straight Chain: all C bonded to only 2
other C
eg. C-C-C-C
– Branched Chain: one or more C bonded
to 3 or 4 other C’s
eg.
C
|
C–C–C
|
C
Classifying Hydrocarbons
Look at the following compounds. If you
were to classify them, how would you do it?
Single Bond Compounds
These are called Alkanes!
Double Bond Compounds
These are called Alkenes!
Triple Bond Compounds
These are called Alkynes!
Classifying Hydrocarbons

These are the three groups of
hydrocarbons
1. Alkane
2. Alkene
3. Alkyne
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We will now look at these further
Alkanes
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Single Bonds C—C
Are saturated hydrocarbons
Each molecule differs from the next by the
structural unit –CH2–
This is a homologous series – when
each member increases by the same
structural unit
The General formula for an alkane is
CnH2n+2
Properties of Alkanes
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Non-polar
Thus are soluble in non-polar solvents
and not soluble in polar solvents
Remember: Like Dissolves Like
Have relatively low boiling points
Boiling points, melting points and
densities of straight-chain alkanes
increase with increasing chain length
Naming Straight-Chain
Alkanes
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All alkanes end with the suffix –ane
Root of the name is based on the
number of carbons in the chain
Examples:
Methane
Ethane
1 Carbon
2 Carbon
What is the molecular formula of each?
Prefix
# Carbon Atoms
Meth
1
Eth
2
Prop
3
But
4
Pent
5
Hex
6
Hept
7
Oct
8
Non
9
Dec
10
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What is the name of this compound?
CH3—CH2—CH2—CH2—CH3
Draw the structure for this compound.
Octane
Naming Branched-Chain
Alkanes
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These molecules have side chains
(branches) that can be made up of alkyl
groups or halogens
We name these based on their parent
chain (longest alkane) and side chains
Naming follows the general formula:
Prefix + Root + Suffix
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Prefix: the branches attached to the
parent chain
Root: the longest continuous chain in
the hydrocarbon (the parent chain)
Suffix: for all alkanes, the suffix is –ane
Alkyl Branches
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Alkyl groups are alkanes with one less
hydrogen
They are named as alkanes are, with
the ending –yl
Eg. Alkane:
Alkyl Group:
Propane CH3CH2CH3
Propyl
CH3CH2CH2
Halogen Branches
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Halogen branches are given names
based on their element name, with any
ending removed
Eg.
Br
Cl
Bromo
Chloro
Naming the branches
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Prefixes are numbered based on their
position along the parent chain – these
numbers are always given such that the
branch has the lowest possible number!
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When putting prefixes together in the
name:
– Numbers are put in ascending order
– Hyphens separate numbers and words
– Commas separate numbers
How does this go together?
CH3–CH–CH2–CH3
|
CH3
Steps for Naming
1.
2.
3.
4.
Find the root – locate the parent alkane
Find position numbers – number the
parent chain starting with the end
closest to the branch
Find the prefix – name the branches
Put it together!
Prefix + Root + Suffix
Try One More
Cl
|
CH3–CH—CH—CH2CH3
|
CH2–CH3
Recap of Naming
1.
Find the root – locate the parent alkane (the
longest carbon chain – it is not always a
straight line!)
2.
Find position numbers – number the parent
chain starting with the end closest to the
branch
3.
Find the prefix – name the branches
4.
Put it together!
Prefix + Root + Suffix
When putting a name together…
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Commas separate numbers from
numbers
Hyphens separate numbers from
letters
Numbers are put in ascending order
ie. 1,2,3
When putting a name together…
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Branch names are placed in alphabetical
order
Except!!!!
When using di and tri for multiple branches,
we order by the branch name and not the
prefix
eg. dimethyl - order by the “m” not the “d”