Classifying Hydrocarbons
Organic Chemistry: Defined as the study of carbon compounds.
Most organic compounds are classified as hydrocarbons. (Hydrocarbon--- hydrogen
bonded to carbon)
The molecular structures of hydrocarbons determine how they are classified.
(Diagram needed here)
Properties of Hydrocarbons
Alkanes
(Parafins)
CnH2n+2
C1H4 CH4
Methane
C2H6
Ethane
C3H8
Propane
Hydrocarbon
with only
single bonds
Alkenes
(Olefins)
CnH2n
Hydrocarbon
with at least
one double
Non-polar
molecules;
low
solubility
in water
Low
boiling
points
(boiling
point
increases
as the size
of the
molecule
increases)
Generally
not very
reactive
(when they
do react, it
is very
slow) An
exception
is a
complete
combustion
reaction
which is
very fast
and very
explosive
Slow substitution
reactions in the
presence of light
Boiling
points are
slightly
Much more
reactive
than
Fast addition
reactions
Propene
C3H6
bond;
unsaturated
Alkynes
CnH2n-2
C3H4
Propyne
Hydrocarbon
with at least
one triple
bond
less than
those of
alkanes
alkanes
Slow substitution reaction:
light
CH3-CH3 + Br-Br ----------- CH3-CH2Br + HBR
Colourless orange (slow) colourless turns litmus paper red
Fast Addition reaction:
CH2-CH2 + Br-Br ---------------- CH3-CH2Br
Colourless orange fast colourless
Hydrocarbons
Organic Chemistry: Defined as the study of carbon compounds.
Most organic compounds are classified as hydrocarbons (hydrocarbon ---- hydrogen
bonded to carbon).
Hydrocarbon: An organ (living compound that contain on carbon and hydrogen atoms in
their structure.
The molecule structures of hydrocarbons determine how they are classified.
Classifications:
A. Aliphatic Compounds: Organic compounds with a molecular structure in which the
carbon chains are straight or ringed (cyclic). They include:
1. Alkanes
2. Alkenes
3. Alkynes
B. Aromatic Compounds: Organic Compounds that contain a benzene ring (C6H6(1))
Organic Nomenclature
The system of nomenclature developed for organic compounds is called the IUPAC
system.
Hydrocarbons are studied and named based on:

Bond (single/double/triple)

Atom arrangement

Number of atoms
In this course, we will look at 4 classes of hydrocarbons;
1. Alkanes (straight chained, single bonds)
2. Alkenes (straight chained, double bonds)
3. Akynes (straight chained, triple bonds)
4. Cyclo”_____” (ring/cyclic structure)
Alkanes
Alkanes (Parafins) --- CnH2n+n
Alkanes ------ aliphatic hydrocarbons that are composed of only hydrogen and carbon
atoms, held together by single bonds.
HHH
H-------C-------C-------C-------H CH3---CH2----CH3
HHH
Alkanes are named according to the number of carbons with the compound. All alkane
names end in “ane”.
# of
Carbons
Formula
Name
1
CH4
Methane
2
C2H6(CH3CH3)
Ethane
3
C3H8(CH3CH2CH3)
Propane
4
C4H10(CH3(CH2)2CH3)
Butane
5
C5H12(CH3(CH2)3CH3)
Pentane
6
C6H14(CH3(CH2)4CH3)
Hexane
7
C7H16(CH3(CH2)5CH3)
Heptane
8
C8H18(CH3(CH2)6CH3)
Octane
9
C9H20(CH3)(CH2)7CH3
Nonane
10
C10H22(CH3)CH2)8CH3)
Decane
Lewis Diagram
Most organic compounds have side chains or branches. These side chains are known as
alkyls and the main chain is called the parent.
When naming alkyl side chains, the same nomenclature seen for the alkanes is used. Only
the “ane” ending become the “yl” ending.
The procedure to be followed when naming branched alkanes is as follows:
1. Find the longest continuous carbon-carbon chain. This is the parent chain. (Not always
straight line).
2. Number the parent chain, starting at the end closest to the 1st branch.
3. Identify the branch and its numerical position.
4. Attach the number and name of the branch in front of the name of the parent.
5. When more than one branch exists, arrange them in alphabetical order.