Fuels and Heats of Reaction
Chapter 21
What is organic chemistry?
Organic Chemistry
• Organic means living
• Organic Chemistry is the study of the compounds of
carbon
• Covalent compounds C bonding with itself and other
elements
• Organic chemistry is the study of pharmaceuticals,
detergents, synthetic fibres, dyes, paints, fossil
fuels, explosives and adhesives
1. Hydrocarbons
A hydrocarbon is a compound that contains only
hydrogen and carbon
Sources: coal, natural gas (methane) and petroleum
(crude oil)
Formed millions of years ago and referred to as fossil
fuels.
Fossil Fuels are fuels that were formed from the
remains of plants and animals that lived millions
of years ago
1. Hydrocarbons
Three main classes:
– Alkanes
– Alkenes
– Alkynes
Alkanes
•
CnH2n+2
The bond between
atoms are all single : Saturated compound
A saturated compound is one in which there are
only single bonds between the atoms in the
molecule
Names and formulas of first 10
alkanes:
1.
Methane – CH4
2.
Ethane – C2H6
3.
Propane – C3H8
4.
Butane – C4H10
5.
Pentane – C5H12
6.
7.
8.
9.
10.
Hexane – C6H14
Heptane – C7H16
Octane – C8H18
Nonane – C9H20
Decane – C10H22
Properties
1.
Good fuels: - lots of heat energy made
- COMPLETE COMBUSTION  H2O + CO2
- Short chains are best (cleaner + less energy to
break)
2.
Do not dissolve or react with water or reactants dissolved in
water: - no energy to break the unreactive C-C or C-H bonds.
3.
Oily
4.
Naturally occuring
Properties
• The first four (methane – butane) are gases at
RTP
• As the number of carbon atoms increases, the
melting points, boiling points and densities
increase
• 5-17 C atoms = liquids
• 18+ C atoms = solids
• C-C bonds and C-H bonds are very strong, so
alkanes are not very reactive
Homologous Series
Definition
• A series of compounds of similar chemical
properties
• Showing graduations in physical properties
• Having a general formula for it members
• Each member having similar preparation
method
• Each member differing from the previous by a
CH2 unit
Make a model of C4H10
Is it possible to build more than one structure?
Isomers
Butane
Methylpropane
2 different compound with different physical
properties : Structural Isomers
Structural Isomers
Structural isomers are compounds with the
same molecular formula but different structural
formula
How many isomers has C5H12?
Naming Alkanes
Note for side chains :
• Alkyl group – alkane with H removed
• Methyl group – CH3
• Ethyl group – C2H5
• Propyl group – C3H7
If 2 alkyl groups present – di- prefix i.e. dimethyl
IUPAC System of Naming Organic Compounds
IUPAC System of Naming Organic Compounds
Naming Branches as “Groups”
Naming Branches as “Groups”
Other Groups We May Encounter
Group Formula
Name
Structure
Group Formula
Name
Structure
–C4H9
iso-butyl
–F
fluoro
–F
–C4H9
sec-butyl
–Cl
chloro
–Cl
–C4H9
tert-butyl
–Br
bromo
–Br
–C5H11
neo-pentyl
–I
iodo
–I