CHAPTER 3
BY
MAHWASH HAFEEZ
They are also called paraffins because of their little affinity to
react with others as the word paraffin is a combination of two
words. i.e. “Para” meaning “little” and “affinity” means “reacting
power”.






For naming the alkanes sytematically first we have to
study about the following four features:
(a) Root word
(b)Primary suffix
(c)Secondary suffix
(d)Prefix
ROOT WORD:(PARENT CHAIN/MAIN CHAIN)
It means the carbon chain. Some commonly used
root words in alkanes are:











Chain length
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
Root Word
MethEthPropButPentHexHept
OctNonDec-
Name of Carbon Chain
 (1) Saturated
(CH3 – CH3)
Primary Suffix
-ane
IUPAC name
Alkane







Functional Group
Alcohol ( -OH )
O
Aldehyde( -C - H )
O
Ketone(-C-)
O
Carboxylic acid ( -C - OH)
Amine(-NH2)
O
Amides(-CNH2 )
Secondary Suffix
-ol
-al
-one
-oic acid
-amine
-amide








Prefixes are added to the root word to indicate the
presence of one or more substituents on the main
carbon chain. These prefixes include:
fluoro(-F)
Chloro(-Cl)
bromo(-Br)
Ido(-I)
Nitro(-NO2)
Alkoxy(-O-R)
Alkyl groups


The prefixes, root words, primary and secondary
suffixes are arranged as follows while writing the
name of an alkane.
IUPAC name = Prefixes + Root word + Primary
Suffix + Secondary suffix
The base or parent chain of alkane is determined by the
longest chain of carbon atoms in the formula. The longest
chain may be bend or twist. It is seldom horizontal.
CH3
CH3-CH2-CH2-CH2-CH2
|
|
CH3-CH2-CH2
CH2
CH2
|
|
|
CH3-CH2-CH-CH2-CH-CH3
CH3
7 CARBON CHAIN
8 CARBON CHAIN

If one substituent or functional group is attached to the
parent chain, then numbering should start from the side
to give minimum number to the substituent. e.g.
1
CH3
|
8CH -7CH -6CH
2 CH
3
2
2
2
|
|
5CH -4CH -3CH-CH
2
2
3
The name of this compound is 3- methyl- octane.
If we start the numbering from left side, it will
give “6” position to methyl group. So that will be wrong.

If more than one similar prefixes are attached to the
same parent chain, then the words “di”, “tri”, “tetra”
etc. are added depending upon how many times the
prefix is attached.e.g.
The name of this compound will be:
3,5-dimethyl octane.
CH3
|
CH3-CH2-CH2
CH2
|
|
CH3-CH-CH2-CH-CH3

If more than one similar functional groups are
attached to the same parent chain, then the words
“di”, “tri”, “tetra” etc. are added depending upon how
many times the functional group is attached.e.g.
The name of this compound will be:
Octa-3,5-di-ol.
CH3
|
CH3-CH2-CH2
CH2
|
|
HO-CH-CH2-CH-OH
6
5
4
3
2
1
CH3-CH2-CH-CH2–CH2-CH2-OH
|
CH3
In the above given example
 Prefix= Methyl
 Root word = Hex (because number of Carbons = 6)
 Primary suffix= ane (because all the bonds are single)
 Secondary suffix = ol ( the functional attached is OH)
 Hence the name of the given compound is
4-methyl hexane-1-ol

6
5
4
3
2
1
CH2-CH-CH2-CH –CH2-CH2-OH
|
|
|
OH CH3
CH3
3,5-dimethyl-hexane-1,6-di-ol.
Draw the following compounds
3,4-diethyl-5-methyloctane
Solution
Name
3,4-diethyl -5-methyl
oct
Prefix
+ parent

ane
+ suffix
C-C-C-C-C-C-C-C octane
CH2-CH3 CH3
CH3- CH2- CH- CH - CH - CH2- CH2- CH3
CH2-CH3
Number of
carbon atoms

Compound
Alkane
name
1 (meth)
2(eth)
CH4
C2H6
Methane
Ethane
3(prop)
C3H8
4(but)
C4H10
5 (pent)
6 (hex)
7(hept)
8 (Oct)
9 (non)
10 (dec)
11 (undec)
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
C11H24
Application
Found in natural gas
Found in natural gas
And used for making ethylene
Propane
Used in heating as liquefied
petroleum gas (LPG)
Butane
Used in heating as liquefied
petroleum gas (LPG)
Pentane
Part of gasoline
Hexane
Part of gasoline
Heptanes
Part of gasoline
Octane
Part of gasoline
Nonane
Part of gasoline
Decane
Part of kerosene
undecane
Part of kerosene
The structure of molecules determines their physical
properties and the way one molecule interacts with
another molecule. Because molecules are normally too
small to see, chemists have devised ways to visually
represented molecules

Alkane also exist in a ring form namely cycloalkane.
Cyclopropane
Cyclobutane
Cyclopentane Cyclohexane
To name the cycloalkane use the following steps:
1) Determine the parent name of compound
2) Add the prefix cyclo to the parent name
3) Name any alkyl group substituent
4) Determine the position of alkyl group or group in the ring
a) For a ring with one alkyl group attached, you don’t
need a number to designate the group's position
Methylcyclohexane
b) When a ring has more than one group attached, number the
ring to give the lowest sum of numbers, assign the groups
alphabetically:
2
3
4
1
6
5
1-ethyl-2-methylcyclohexane
c) If the sum number of groups is identical either direction
around the ring then count towards the second group
alphabetically on the ring
3
4
2
5
1
6
1-ethyl-5-methyl-3-propylcyclohexane
5) The more complex ring containing alkanes need the
following addition steps to name compound
i) When the alkane chain is complex or has more carbons than
the ring, name the ring as substituent
3-cyclobutylheptane
3-cyclopropylpentane
When one ring is attached with to another ring consider the
larger ring the parent name
Cyclopropylcyclobutane
 Hydrogenation
of alkenes:
Alkanes can be prepared by
catalytic hydrogenation of alkenes. i.e.
Ni (or Pt)
CH2 = CH2 + H2
CH3 – CH3
25 oC
Corey House Reaction:
An alkane can be formed by reacting lithium
dialkylcopper i.e. R2CuLi(organometallic compound)
with alkyl halide.
R2CuLi + R – X  R – R + RCu + LiX

 Wurtz
Reaction:
When an alkyl halide is treated with sodium metal
in the presence of ether, an alkane is formed.
R – X + Na ether
R – R + NaX
Kolbe’s reaction:
Electrolysis of a concentrated solution of sodium salt of
carboxylic acid gives an alkane.
O
electric current
R – C – ONa
R – R + CO2 + H2O + NaOH

Physical State:
Alkanes with 1-4 Carbon atoms are gases.e.g.
Natural gas.
Alkanes with 5-7 Carbon atoms are liquids. e.g.
petroleum, gasoline.
Alkanes with more than 8 Carbon atoms are solids.
e.g. paraffin wax.
 Boiling Point:
Boiling point of alkanes increase with increasing
molecular mass.

 Melting
Point:
Melting points of the alkanes also increase with the
increase in the number of carbon atom. Moreover the
branched chain alkanes are likely to have high melting
points than straight chain alkanes of the same molecular
weight.
 Solubility:
Alkanes being non-polar, are soluble in non-polar
solvents such as CCl4, ether and benzene. They are
generally insoluble in water.
 Density:
The density of liquid alkanes increases slightly with
increase in the size of the molecules due to the
increasing intermolecular van der Waals’ forces
which cause the alkanes to be more compact in the
condensed liquid state.
1. Halogenation
2. Combustion (oxidation)
1) Halogenation
If there is one type of the carbon atoms in the molecule
(e.g. methane and ethane)
Alkanes react slowly or not at all with bromine at room
temperature in the dark, but in the presence of sunlight,
substitution is fairly rapid:
R-H + Br2 /light R-Br + HBr
(a substitution reaction)

If there is one type of the carbon atoms in the molecule
(e.g. methane and ethane)
H
H
H – C – H + Cl – Cl  H – C – Cl + HCl energy
H
H
Methane
methyl chloride
Cl
H–C–H
Cl
Dichloromethane
(Methylene
chloride)
Cl
Cl – C – H
Cl
Trichloromethane
(Chloroform)
Cl
Cl – C – Cl
Cl
Tetrachloromethane
(Carbontetrachloride)
If there are different types of carbon atoms in the molecule
(Selectivity issue)
When alkanes larger than ethane are halogenated, isomeric
products are formed. Thus chlorination of propane gives both
1-chloropropane and 2-chloropropane as mono-chlorinated
products.
H3C1
2
1CH3+
Cl – Cl Heat or UV light H3C
CH3+H3C
Cl
Cl
Propane
Major
Minor
It is the detailed, step. by step description of chemical reaction.
1- Cl2
2Cl
Chain initiating step
.
.
 2- Cl + CH4
HCl + CH 3
Chain propagating step
.
.
 3- CH 3 + Cl2
CH3Cl + Cl Chain propagating step



Then step 2, step 3, step 2, step 3, etc.
.
.
4- Cl + Cl
Cl2
terminating step
.
.
5- CH 3 + CH 3
CH3- CH3
terminating step
.
.
6- CH 3 + Cl
CH3- Cl
terminating step
2. COMBUSTION:
a) In complete combustion :
2C8H18 + 17O2
16CO
+
18 H2O
carbon monoxide
b) Complete combustion:
Alkanes readily burn in the presence of oxygen
or air and are oxidized to carbondioxide and water with
the evolution of large amount of heat.
For example:
CH4 + O2 flame CO2 + H2O + 891Kj/mol

Catalytic Reforming:
When alkanes containing 6 or more carbon atoms
are heated at 450 – 500oC under pressure in the presence
of a catalyst, they form aromatic compounds.
For example:
CH3-CH2-CH2-CH2-CH2-CH3
Hexane

+ 4H2
Benzene
Isomerization:
Straight chain alkanes in the presence of
aluminium chloride, small amounts of hydrogen
chloride and any alkene at 300 oC isomerize to branched
chain alkanes.
For example:n-butane isomerize to iso butane.
CH3-CH2-CH2-CH3 RCH=CH2+HCl CH3-CH-CH3
AlCl , 300oC
3
CH3
Example : Complete the combustion reaction for
C3H8 + O2
+
Balance your equation
Example2 :Complete and balance the reaction for the
complete combustion of C7H16
Combustion In the Cell
Metabolic oxidation is combustion
C6H12 O6 + 6O2
6CO2 + 6H2O + heat
glucose
 2-bromo-2-chloro-1,1,1-trifluoroethane
is used as anethetic.
Cl F
H–C–C–F
Br F
2-bromo-2-chloro-1,1,1-trifluoroethane
 Chloral hydrate induce sleep and prevent convulsions.
Cl OH
Cl – C – C – H
Cl OH
Chloral hydrate
 Polyvinyl
chloride is used in making plastics container
and pipes
H
C
H
 Fereon-12
H
C
Cl
n
is used in aerosol container, refrigerator and
in air condition.
Cl
F
H
C
C
H
Cl
F
Fereon – 12

Teflon is used as coating material for cooking
utensils
F
C
F
F
C
H n


The main sources of hydrocarbons are petroleum and natural gas
The Petroleum is a mixture of hydrocarbon that formed over millions
years.
Petroleum fraction
fraction
Boiling point
Molecular
size
Natural gas
-164 oC
C1-C2
LPG
C3-C4
Gasoline
30-200 oC
C5-C12
Kerosene
175-275 oC
C12-C16
o
Solar(diesel oil) Up to 375 C
C15-C18
Lubricating oil
˃350 oC
C16-C20
Greases
Semisolid
˃ C18
Paraffin
Melts 52-57
˃ C20
Pitch and tar
Residue in boiler
high
Typical uses
Heating-cooking
Motor fuel
Fuel for stoves & jetengine
Furnace oil
Lubrication
Lubrication
Candles, toiletries
Roofing, Asphalt, paving
One measure of quality of gasoline is octane number
 Octane number of a gasoline refer to how smoothly it burns
 A low octane number of gasoline burns too rapidly and causes the
engine to knock
 A high octane number gasoline delivers power smoothly to the
piston.

CH3
CH3
CH2– CH
CH3
CH3
CH3-CH2 - CH2 - CH2 - CH2 - CH2 - CH3
CH3
Isooctane
2,2,4-trimethylpentane
octane number 100%
n-heptane
octane number 0%