LOGO
Lecture 4 :
Alkanes
Organic Chemistry – FALL 2015
Course lecturer :
Jasmin Šutković
4th November 2015
Contents
International University of Sarajevo
Book chapter 12
12.1 Introduction
12.2 Simple Alkanes
12.3 An Introduction to Nomenclature
12.4 Alkane Nomenclature
12.5 Cycloalkanes
12.6 FOCUS ON THE ENVIRONMENT:
Fossil Fuels
12.7 Physical Properties
12.8 FOCUS ON THE ENVIRONMENT:
Combustion
Introduction
 Alkanes are hydrocarbons having only
C-C and C-H single bonds.
 The carbons of an alkane can be joined together to
form chains or rings of atoms.
 Alkanes that contain chains of carbon atoms but no
rings are called acyclic alkanes.
 An acyclic alkane has the molecular formula CnH2n + 2,
where n is the number of carbons it contains.
 Acyclic alkanes are also called saturated
hydrocarbons because they have the maximum
number of hydrogen atoms per carbon.
Simple Alkanes – Acyclic alkanes
We will start with smaller molecules, small number
of C atoms.
Mehane (CH4) and Ethanne (C2H6)
Common fetures of Alkanes
Single bonds!
Have isomers ...starting with Propane, Butane ....
Isomer = samle molecular formula but different
structures
Constitutional isomers
Cis and Trans isomerism
Alkanes having 5 or more
C atoms
Example problem
The most common multiple bond between C and a heteroatom is
carbon – oxygen double bond.
Carbon forms 4 stable bonds with itself and other elements. Carbon
atoms bind together to fotm RINGS or CHAINS
CLASSIFICATION OF
Carbon atoms
Functional groups
 The structural features that make it
possible to classify compounds into
families are called functional groups.
 A functional group is a group of atoms
within a molecule that has a characteristic
chemical behavior
-
Nomenclature
 Hydrocarbon chains where all the bonds
between carbons are SINGLE bonds
 Name uses the ending –ane
 Examples: Methane, Propane, Butane, Octane,
2-methylpentane
Summary: IUPAC Rules
for Alkane Nomenclature
1. Find and name the longest continuous carbon chain. This is called
the parent chain. (Examples: methane, propane, etc.)
2. Number the chain consecutively, starting at the end nearest an
attached group (substituent).
3. Identify and name groups attached to this chain. (Examples:
methyl-, bromo-, etc.)
4. Designate the location of each substituent group with the number
of the carbon parent chain on which the group is attached. Place a
dash between numbers and letters. (Example: 3-chloropentane)
5. Assemble the name, listing groups in alphabetical order.
The prefixes di, tri, tetra etc., used to designate several groups of
the same kind, are not considered when alphabetizing. Place a
comma between multiple numbers. (Example: 2,3-dichloropropane)
Step 1. Find the parent
chain.
 Where is the longest continuous chain of
carbons?
Prefixes for # of Carbons
1
Meth
6
Hex
2
Eth
7
Hept
3
Prop
8
Oct
4
But
9
Non
5
Pent
10
Dec
Endings
 Alkanes (all C-C single bonded parent chain)
end in –ane
 Methane CH4
 Ethane C2H6
 Propane C3H8
 Attached carbon groups (substituents) end in –yl
 Methyl CH3  Ethyl CH3CH2 Propyl CH3CH2CH2 –
3-ethylpentane
Step 2. Number the
parent chain.
 Number the parent chain so that the
attached groups are on the lowest
numbers
Methyl is on carbon #2 of the parent chain
Methyl is on carbon #4 of the parent chain
1
5
1 8
2
4
3
3
4
2
3 6
7 2
8 1
4 5 5 4
6 3
5
1
GREEN is the right
way for this one!
27
Groups on 4, 6, and 7
Groups on 2, 3, and 5
1
7
2
6
3
5
4
4
Groups on 2 and 5
Groups on 3 and 6
5
3
6
72
1
Step 3. Name the attached
groups.
 Carbon (alkyl) groups
 Methyl CH3  Ethyl CH3CH2 Propyl CH3CH2CH2 –
 Halogens




Fluoro (F-)
Chloro (Cl-)
Bromo (Br-)
Iodo (I-)
Step 4. Designate where the group
is attached to the parent chain.
 Use the numbers of the parent chain from
step 2 to designate the location of the
attached groups to the parent chain.
2-methyl
1
2
3
4
5
Step 5. Alphabetize the groups,
combine like groups, and assemble.
 The prefixes di, tri, tetra
etc., used to designate
several groups of the
same kind
 Prefixes are not
considered when
alphabetizing (Example:
dimethyl = m for
alphabetizing)
 Parent chain goes LAST
1,1,1-trichloro-1fluoromethane
1,1-dichloro-1,1difluoromethane
CYCLOALKANES
Examples of cycloalkanes
 The smallest alkane that can form a ring is
cyclopropane, C3H6, in which the three
carbon atoms lie in the same plane.
 The angle between adjacent CC bonds is
only 60° as seen in the model below:
Molecular models of
cycloalkanes
cyclohexane
cyclobutane
cyclopropane
cyclopentane
Naming the cycloalkanes:
 Find the longest continuous loop of carbon
atoms in the skeleton structure.
 Name the compound as a derivative of the
cycloalkane with this number of carbon
atoms: 3-C = cyclopropane
4-C = cyclobutane
5-C = cyclopentane
Name the following
cycloalkanes:
Rings (or cyclic compounds) are composed of rings of carbon and
sometimes oxygen or nitrogen. For example, cyclohexane has a ring of six
carbon atoms.
cyclopropane
cyclobutane
cyclopentane
cyclohexane
cyclohexane
bromocyclohexane
cyclohexene
Examples
Give the IUPAC name
Human life – fossile fuels
• Alkanes are found in nature, natural gas and petroleum.
• Natuaral gas and petroleum represents fossile fuels and are used as
energy sources
• Natural gas in composed minimum of 60% methane , rest is
ethane, propane and butane.
• Petroleum is a complex mixture of compounds ( up tp 40 C atoms),
giving FUELS .
Focus on environment combustion
Combustion is a form of REDOX reaction – Oxidation – Reduction
Physical properties
• Alkanes are used primarily as fuels, solvents, and lubricants. Natural gas,
gasoline, kerosene, heating oil, lubricating oil, and paraffin “wax” are all
composed primarily of alkanes, with different physical properties resulting
from different ranges of molecular weights.
• Alkanes are hydrophobic
•Alkanes are good lubricants and preservatives for metals because they
keep water from reaching the metal surface and causing corrosion.
Boiling point
Major uses of Alkanes
Chemical reactions
Homework 2
1. Combustion
2. Halogation
3.Use of Methane
2 page essay with few examples !!!!