Unit 2
Introduction to
Hydrocarbons
Differences between organic
and inorganic compounds:
1. Organic compounds are mostly covalent
molecules where most inorganics are ionic
2. Most organics don’t dissolve in water
and most inorganics do
3. Organic compounds decompose on
heating easier than inorganics
4. Organic reactions are much slower
(min, hours, days) than inorganic
reactions (seconds)
Fun Facts (Don’t have to Copy)
More than 18 Million organic
compounds [with 10,000
new ones discovered each
year]
1.7 Million inorganic
compounds so about 85% of
compounds are organic
2 Reasons for the abundance of
organic compounds:
Carbon atoms bond to each other to form
long chains(up to 200 carbons)
Catenation – the ability of an element to bond
to itself
The same number of carbon atoms can
rearrange to form different structures
(isomers)
Isomer – compounds with the same molecular
formula but different structures
Isomer Example
 C5H12
C
 -C-C-C-C-C-
-C-C-C-C-
C
-C-C-CC
How Carbon Bonds
 C ground state is 2s22p2 but bonds as
*2s12p3 giving 4 sp3 hybrid orbitals
 Hybrid orbitals – orbitals of equal energy
formed by mixing orbitals of different
energies
 Hybridization – the mixing of orbitals of
different energies to give orbitals of equal
energy
How Carbon Bonds
Carbon’s 4 covalent bonds
form a tetrahedron (109.5°
bond angle)
Hydrocarbons!
Hydrocarbons – compounds
containing only hydrogen
and carbon
Alkanes – hydrocarbons
that have all C-C single
bonds
Naming
# of
C
Name
1
Structural
Formula
Methane -C-
Condensed
Formula
CH4
Molecular
Formula
CH4
2
Ethane
CH3CH3
CH3CH2 CH3
CH3(CH2)2 CH3
CH3(CH2)3 CH3
CH3(CH2)4 CH3
CH3(CH2)5 CH3
CH3(CH2)6 CH3
C2H 6
C3H 8
C4H10
C5H12
C6H14
C7H16
C8H18
CH3(CH2)7 CH3
C9H20
CH3(CH2)8 CH3
C10H22
3
4
5
6
7
8
9
10
-C-CPropane -C-C-CButane
-C-C-C-CPentane -C-C-C-C-CHexane -C-C-C-C-C-CHeptane -C-C-C-C-C-C-COctane
-C-C-C-C-C-C-CCNonane -C-C-C-C-C-C-CC-CDecane -C-C-C-C-C-C-CC-C-C-
Naming
*Know roots and endings*
 Each step, you add a CH2 group
 Homologous Series – a series of
compounds where each member
differs from the next by a constant
unit (CH2)
 Members are called homologous
 Since alkanes are homologous – we
can write a General Formula = CnH2n+2
Naming
Alkanes are Saturated
Hydrocarbons –
hydrocarbons where each C
has 4 single covalent bonds
(no more atoms can be
added)
Alkenes
 Alkenes – hydrocarbons with one C=C double
bond – sp2 hybridization on the 2 C atoms in
the double bond.
 Ethene
C=C
CH2CH2
C2H4
 Propene
C=C-C
CH2CHCH3
C3H6
 Butene
C=C-C-C
CH2CHCH2CH3
C4H8
 Octene
C=C-C-C-C-C-C-C-
CH2CH(CH2)5CH3 C8H16
Ways to Show Organics
Line
Bond
Form
Space Filling
Model
Ball and Stick
Form
Structural
Formula
Skeletal Form
Alkenes
Also a homologous series General
Formula CnH2n
Unsaturated hydrocarbons – have C-C
multiple bonds which can be broken to add
more atoms to the molecule
H
Ex:
H
C=C
H
H
H
+ H2 
H
H-C -C-H
H
H
Alkynes
 Alkynes – hydrocarbons containing a C = C
triple bond – sp hybtidization
 Ethyne
-C=C-
CHCH
C2H2
(acetylene)
 Propyne -C=C-C-
CHCCH3
C 3 H4
 Butyne
-C=C-C-C-
CHCCH2CH3
C 4 H6
 Heptyne
-C=C-C-C-C-C-C-
CHC(CH2)4CH3
 General Formula = CnH2n-2
C7H12
Alkadienes
 Alkadienes – hydrocarbons containing two
C=C double bonds
 Butadiene
-C=C-C=C-
 Pentadiene -C=C-C=C-C-
CH2(CH)2CH2
C4H6
CH2(CH)3CH3
C5H8
 Heptadiene
-C=C-C=C-C-C-CCH2(CH)3(CH2)2CH3
General Formula = CnH2n-2
C7H12
Alkadienes
3 placements for the two double bonds
Conjugated double bonds (most
common) – two double bonds separated
by one singe bond
Isolated double bonds – two double
bonds separated by more than one
single bond
Allenes – hydrocarbons that have two
consecutive double bonds
The first 4 Series of
hydrocarbons are Aliphatic
Hydrocarbons
Aliphatic hydrocarbons –
hydrocarbon where carbon
atoms bond together in open
chains
Arenes
 Aromatic Hydrocarbons – hydrocarbons
containing rings of 6 carbon atoms joined
by alternating single and double bonds
 Simplest aromatic hydrocarbon = benzene
Arenes
All bonds are actually identical (C-C
and C=C “mixed”)
Can also be shown as
Arenes
We use
The e-‘s are actually shared by all 6
carbons and move freely around the
ring (delocalized)
This makes benzene behave like
saturated hydrocarbons
Resonance
Compounds like these are
resonance hybrids (compounds
that can be represented by
more than one Lewis structure)
General Formula = CnH1/2n+3
Resonance examples
IUPAC Naming Rules
1. Name the longest chain (the parent chain) first.
2. Label the chain to give the lowest numbers to
groups or bonds. Priority  C=C then C=C You
give the number for the carbon where the multiple
bond begins. (Separate numbers and words with a
hyphen, and numbers and numbers with a
comma).
6 5 4 3 2 1
 C-C-C-C=C-C
2 –hexene
 C-C-C=C-C-C-C
3 – heptyne
IUPAC Naming Rules
3. Give the numbers for any attached groups
for the carbons they are attached to, a
number for each attached group. Use the
number with the groups name. [in front of
“main” chain]
a) If more than one of any group = di-, tri-,
tetra-, penta-, hexa-, etc.
b) Group Names:
 F = fluoro
I = iodo
 Cl = chloro
OH = hydroxo
 Br = bromo
NO2 = nitro
IUPAC Naming Rules
c. If there is more than one group
attached, the names are listed in
alphabetical order (ignore prefixes) in
front of the “main” chain
d. If the numbers for the side groups
are the same from either side of the
chain, # from the side that gives the
lowest # to the first group in the
alpha order.
Summary
Hydrocarbons (straight chains)
Locate and name attached groups
Locate multiple bonds (priority for
numbering)
Name base/parent chain
IUPAC Naming Rules
4. Branched chains
Longest continuous chain containing
any multiple bonds (if present)
# to give multiple bonds lowest
numbers (priority)
Name side groups (alphabetical order)
IUPAC Naming Rules
1-chloro-3,5 - dimethylbezene
5. Benzene
Number starting with a C bonded to an
attached group and then continue around
the ring
Use the lowest set of #’s possible
IUPAC Naming Rules
 1,3 – dibromo – 2 – fluorobenzene
IUPAC Naming Rules
c. If there are just two of the same group
attached, we can use the following terms
to simplify the bonding positions
Ortho = 1, 2 bonding position
Meta = 1, 3 bonding position
Para = 1, 4 bonding position
O,M, P
Isomer Practice
Isomers – compounds having
the same molecular formula but
having different structures
 Example: C5H11Cl
 Draw all isomers by moving
Cl (we are only going to use
straight chains for C’s)
Isomer Practice
Cl

C–C–C–C–C
Cl

C –C – C – C – C
Cl
 C–C–C–C–C
Isomer Practice
C4H8Cl2
Isomer Practice
Try C4H8ClI, C4H7I3,
C5H10FBr, and C4H7F2Br