Transcript Document

Hydrocarbons
Compounds containing hydrogen and carbon only
We get them from crude oil
They are made up of molecules
A molecule is made up of 2 or more atoms joined
by covalent bonds.
Hydrogen is in group 1 and has 1 outer electron
Hydrogen can form one bond
Carbon is in group 4 and has 4 outer electrons
Carbon can form 4 bonds
ALKANES
H
A family of hydrocarbons
Methane
Name
Ethane
H
CH4
H
H
Structural
Formula
H H
Molecular
Formula
C2H6
C
H
C
C
H
H
H
ALKANES
Propane
C3H8
Butane C4H10 H
H
H
H
H
C
C
C
H
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
H
ALKANES
Pentane
H
C5H12
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
Hexane – How many hydrogens?
C6
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H H
H
H
H
H
Each carbon in the chain has a hydrogen above
and below so multiply 6 by two = 12
There is also a hydrogen at each end. Add 2.
Total number of hydrogens
H
= (2x6) + 2
= 12 + 2
=14
H
H
H
H
H
H
C
C
C
C
C
C
H
H H
H
H
H
H
Give the complete formula for each of these hydrocarbons. You
are given the number of carbons.
C8
H18
(2 x 8) + 2
= 16 + 2 =18
C10
H22
(2 x 10) + 2
= 20 + 2 = 22
C15
H32
(2 x 15) + 2
= 30 + 2 = 32
C31
H64
(2 x 31) + 2
= 62 + 2 = 64
C100
H202
(2 x 100) + 2
= 200 + 2 = 202
Cn H2n + 2
(2 x n) + 2
Hydrocarbons
Hydrogen and carbon only
Methane
CH4
My
Ethane
C2H6
Elephant
Propane
C3H8
Prefers
Butane
C4H10
Buns
Pentane
Alkanes
C5H12
Pity
C6H14
He
Heptane
C7H16
Has
Octane
C8H18
Only
Nonane
C9H20
Nice
Decane
C10H22
Doughnuts
Hexane
General
formula
CnH2n+2
H
H
H
C
C
H
H
H
Shortened
structural formula
Structural formula
H
H
H
H
C
C
C
H
H
H
CH3CH3
H
CH3CH2CH3
H
H
H
H
H
C
C
C
C
H
H
H
H
Isomers
H
H
H
H
C C
H
H C
C
H
H
H
H
Both butane
Both C4H10
Same molecular
formula
H
Different structural
formula
In your jotter:
Draw the 3 isomers of pentane
At least 3 isomers of hexane
CYCLOALKANES
Cycloalkanes are ring compounds
The first cycloalkane is:
H
H
C
H
C
C
H
H
Cyclopropane
H
C3H6
The second cycloalkane is:
H
H
H
C
C
H
H
C
C
H
H
H
Cyclobutane
C4H8
The third cycloalkane is:
H H
H
H
H
C
C
H
H
C
C
C
H
H
H
Cyclopentane
C5H10
The fourth cycloalkane is:
H
H
C
H
H H
C
C
H H
C
C
H
H
C
H
H
H
Cyclohexane
C6H12
Cycloalkane
Molecular Formula
Cyclopropane
C3H6
2x3=6
Cyclobutane
C4H8
2x4=8
Cyclopentane
C5H10
2 x 5 = 10
Cyclohexane
C6H12
2 x 6 = 12
Cycloheptane
C7H14
2 x 7 = 14
Cyclooctane
C8H16
2 x 8 = 16
General
formula
CnH 2n
ALKENES
Alkenes are hydrocarbons which have a double bond
H
H
C
C
H
H
Ethene
Double
bond
C2H4
H
H
C
C
C
H
H
H
H
C
H
C
H
H
C3H6
H
H
C
C
H
Propene
H
H
Butene
C4H8
Alkene
Molecular Formula
Ethene
C2H4
2x2=4
Propene
C3H6
2x3=6
Butene
C4H8
2x4=8
Pentene
C5H10
2 x 5 = 10
Hexene
C6H12
2 x 6 = 12
General
formula
CnH 2n
1
2
3
4
a)
b)
5
6
7
8
9
10
Write the molecular formula of:
a) the alkane with 6 carbons b) the alkane with 24 hydrogens
c) the cycloalkane with 20 carbons
d) the alkene with 100 hydrogens
Draw the structural formula of:
a) the alkene with 5 carbons b) the cycloalkane with 7 carbons
Give the general formula of
a) the alkanes
b) the alkenes
c) the cycloalkanes
Copy and complete:
Isomers have the same ____ formula but different ___ formula
Draw 2 isomers of heptane and 2 isomers of butene and 2 isomers
of cyclopropane
What is meant by a hydrocarbon?
What is meant by a molecule?
What is produced when a hydrocarbon burns?
Which would have higher boiling point propane or pentane?
Which would be more flammable octene or butene?
Which would be more viscous cyclopropane or cyclooctane?
Hydrocarbons
Alkanes
Alkenes
-ANE
-ENE
A
E
Single
bond
H
H
H
C
C
H
H
Ethane
H
H
H
C
C
H
H
Ethene
Double
bond
The Bromine Water Test
Place a small amount of each hydrocarbon in a test tube. To each
add a little bromine water. Bromine water is a brownish colour and
when dilute is yellowish.
Set out your results by drawing up a table as shown below
Hydrocarbon
Hexane
Hexene
Heptane
Octane
Hexane
Cyclohexane
Formula
C6H14
C6H12
C7H16
C8H18
C6H14
C6H12
Result of test
Test for ALKENES
H
H
C
C
H
H
Br Br
Br2
H
C
C H
H
H
ETHENE
Bromine water
Decolourised
1
Write out full structural formulae to show the reaction
between:
a) Propene and bromine water
b) Butene and bromine water
2
Complete the following equations by putting in the missing
compounds (first one is done for you).
a)
b)
c)
d)
e)
C5H10 (pentene) + Br2
C6H12 (hexene) + Br2
_____ (_______) + Br2
C4H8 (butene) + Cl2
C5H10 (pentene) + ____





C5H10 Br2
C6H12 Br2
C8H16 Br2
_________
C5H12
ALKANE
H
H
H
C
C
H
H
H
ethane
Single bonds
only
Saturated
ALKENE
H
H
C
C
H
H
ethene
Unsaturated
Has a C=C
double bond.
Hydrocarbon
Cracking
Aluminium oxide
oil (C12H26)
catalyst
Product gas
Heat
water
Do not remove heat before taking the tube out of the water!
The gas produced decolourised bromine water – it contained an
alkene.
The large liquid molecules have been broken (cracked) into smaller
gas molecules.
Thermal cracking produces more useful small molecules from less
useful large molecules.
1
C12H26 
C10H22 +
______ (
)
2
C18H38 
C12H26 +
______ (
)
3
C20H42 
C10H20 +
______ (
)
4
C30H62 
C10H22 + C11H22 + ______ (
5
C19H40 
C12H24 + C6H12 +
6
______ (
) 
)
______ (
C4H8
+ C4H10
)
H
H
C
H
H
C
H
C
H
H
H
C
C
C
H
H
H
H