HYDROCARBONS
ALKANES, ALKENES AND ALKYNES
ORGANIC COMPOUNDS
• Carbon based compounds
• Can be bonded to other elements (H, O, N,
S and halogens)
• Carbon makes 4 bonds, which can be
single, double or triple
• Isomers: same molecular formula (# of each
atom) but different arrangement
TYPES OF HYDROCARBONS
• Saturated: Contain the maximum number of
hydrogens, single bonds between all carbons
• Unsaturated: Contain 1+ double or triple bonds
TYPES OF HYDROCARBONS
• Aliphathic Carbons are arranged in chains
• Cyclic: Carbons are arranged in rings
• Aromatic: Contain a benzene ring
TYPES OF HYDROCARBONS
Name
Alkane
Alkene
Alkyne
Definition
Hydrocarbon with only
single bonds between
carbon atoms.
Hydrocarbon with at
least one double bond.
Hydrocarbon with at
least one triple bond.
General
Formula
C2H2n+2
C2H2n
C2H2n-2
STRUCTURAL SHORTHAND
Explicit hydrogens (those required to complete
carbon’s valence) are usually left off of
drawings of hydrocarbons
H
CH3
H
H
H
H3C
H
C1 C2 C3 C4
H
H
H
H
H
C1 C2 C3
C4
Line intersections represent carbon atoms
HYDROCARBON ROOT NAMES
# of Carbons
1
2
3
4
5
6
7
8
9
10
Root Name
methethpropbutpenthexheptoctnondec-
NAMING ALKANES
Based off the number of C atoms in the
longest chain
1. Count the number of C’s in the longest
chain
2. Determine the appropriate root
3. Add the suffix “ane”
1. 3 carbons
2. 3 Carbons = Prop
3. Propane
NAMING BRANCHED ALKANES
Based off the number of C atoms in the
longest chain
1. Count the number of C’s in the longest
chain
2. Determine the appropriate root
3. Use the numbered C’s to give the
branches a position number add “yl” suffix
4. Add the suffix “ane”
RULES FOR NAMING ALKANES
(NOMENCLATURE)
For a branched hydrocarbon, the longest
continuous chain of carbon atoms gives the
root name for the hydrocarbon
H3C1
2
3
4
H3C
CH3
4 carbon chain = butane
NAMING BRANCHED ALKANES
Important Rules:
1. Start numbering from the end that will give
you the lowest number of branches
2. If there is more than one type of branch,
name the branches in alphabetical order
3. If there is more than two of the same type
of branch, give the branch a position
number and prefixes “di”, “tri” “tetra” etc.
4. Put commas between numbers and
hyphens between numbers and letters
RULES FOR NAMING ALKANES
(NOMENCLATURE)
When alkane groups appear as substituents, they
are named by dropping the -ane and adding -yl.
—CH3 Methyl
—CH2CH3 Ethyl
—CH2CH2CH3 Propyl
—CH2CH2CH2CH3 Butyl
H3C
H3C
Methyl
CH3
RULES FOR NAMING ALKANES
(NOMENCLATURE)
The positions of substituent groups are specified
by numbering the longest chain of carbon atoms
sequentially, starting at the end closest to the
branching.
H3C1
2
3
4
H3C
Methyl
CH3
RULES FOR NAMING ALKANES
(NOMENCLATURE)
The location and name of each substituent are
followed by the root alkane name. The substituents
are listed in alphabetical order (irrespective of any
prefix), and the prefixes di-, tri-, etc. are used to
indicate multiple identical substituents.
H3C1
2
3
4
H3C
Methyl
CH3
Name: 2-methylbutane
NOMENCLATURE PRACTICE
Name this compound
CH3
H3C1 2
Cl
3 4
5
CH3
6
7
9 carbons = nonane
8
H3C9
Step #1: For a branched hydrocarbon, the longest
continuous chain of carbon atoms gives the root name
for the hydrocarbon
NOMENCLATURE PRACTICE
Name this compound
CH3
H3C1 2
Cl
3 4
5
CH3
6
7
8
9 carbons = nonane
CH3 = methyl
chlorine = chloro
H3C9
Step #2: When alkane groups appear as substituents, they are named by
dropping the -ane and adding -yl.
NOMENCLATURE PRACTICE
Name this compound
CH3
H3C1 2
Cl
3 4
5
6
7
9 carbons = nonane
CH3
CH3 = methyl
chlorine = chloro
8
H3C9
1
9 NOT
9
1
Step #3: The positions of substituent groups are
specified by numbering the longest chain of carbon
atoms sequentially, starting at the end closest to the
branching.
NOMENCLATURE PRACTICE
Name this compound
CH3
H3C1 2
Cl
3 4
5
CH3
6
7
9 carbons = nonane
CH3 = methyl
8
chlorine = chloro
H3C9
2-chloro-3,6-dimethylnonane
Step #4: The location and name of each substituent are
followed by the root alkane name. The substituents are
listed in alphabetical order (irrespective of any prefix),
and the prefixes di-, tri-, etc. are used to indicate
multiple identical substituents.
NAMING CYCLIC ALKANES
ADD PREFIX “CYCLO”
Cyclopropane, C3H6
Cyclobutane, C4H8
Cyclopentane, C5H10
Cyclohexane, C6H12
Cycloheptane, C7H14
Remember, explicit hydrogens are left out
NAMING ALKENES & ALKYNES
1. Count the number of C’s in the longest chain
containing the double/triple bond.
•
•
This is the parent chain, determine the root
Number the parent chain so that the double/triple bond
has the lowest possible position number
2. Identify the position numbers of branches
•
Same rules as before
•
Add the prefix “cyclo” if its cyclic
3. Write the branches in alphabetical order
4. Write the root, including a prefix that
identifies the position of the double/triple
bond
5. Add the suffix “ene” if double bond or “yne”
if triple bond
NAMING AROMATICS
Benzene: Cyclic 6 carbon ring of alternating
single and double bonds (which gives it special
properties)
1. Same rules
2. If benzene is the parent chain “benzene”
suffix
3. If benzene is a branch group “phenyl”
CIS/TRANS ISOMERS
Cis
Trans
NAMING HALOALKANES/ALKENES/ALKYNES
• Halogen: group 17, 7 valence shell electrons, form 1
single bond
NAMING HALOALKANES/ALKENES/ALKYNES
• Same rules as a side change
• Side chain name: First part of halogen with –o:
• Fluoro, Chloro, Bromo, Iodo
• Often Represented as R-X
• R = any hydrocarbon chain
• X = halogen
• Ex:
1. Longest chain is 5
carbons = pentane
2. Only side chain is
bromine = bromo
3. Bromine at carbon 1 =
1-bromopentane