Fuels
A “fuel” is something that can be burned to release heat and
light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In
other words, they were made from fossils.
H
Lots of
oxygen:
H
H
O
H
H
+
H
H
H
H
O
H
H
Methane
H
H
O
C
+
H
H
Methane
+
O
C
H
Carbon
dioxide
+
O
C
O
C
O
O
O
Oxygen
O
H
O
O
O
Oxygen
O
C
O
Oxygen
O
C
H
Little
oxygen:
O
C
Methane
Some
oxygen:
Burning Fuels
Carbon
monoxide
+
C
Carbon
+
O
H
H
Water
H
O
H
O
H
O
H
O
H
H
H
H
Water
H
O
H
O
Water
H
H
Alkanes and alkenes combust in Oxygen
Complete combustion in excess oxygen produces a hotter, clean
burning flame.
CH4(g)
+
2O2(g)  CO2(g) + 2H2O(g)
Incomplete combustion - occurs when the combustion is
carried out in a limited supply of air or oxygen. The flame is not
clean burning, but is sooty and yellow coloured. The poisonous
gas carbon monoxide, CO, can also be produced.
CH4(g)
+ 1 ½ O2(g) 
or CH4(g)
+
O2(g)
CO(g) + 2H2O(g)
 C(s) + 2H2O(g)
Pollutants from burning fuels
O
C
O
Carbon dioxide is a _________
greenhouse
gas and contribute to global
warming
_______
Carbon monoxide combines with
haemoglobin in the _____
blood and
___________
reduces the ability for red blood
oxygen
cells to carry _______.
O
C
Fractional distillation
Crude oil can be separated by fractional distillation. The oil is evaporated
and the hydrocarbon chains of different lengths condense at different
temperatures:
Fractions with
low boiling
points condense
at the top
Fractions with
high boiling
points condense
at the bottom
Summary Properties of Alkanes






Insoluble in water
Soluble in non polar solvents
Don’t conduct – no free electrons
Float on water because H2O is polar and more
dense
Boiling/melting point increases with chain length
because as molecular mass increases the
intermolecular forces between molecules
increases
All alkanes are saturated hydrocarbons because
they are saturated with H atoms
Structural isomers
The alkanes we have looked at so far are all called ‘straight
chained alkanes.
 Alkanes with 4 or more C atoms can also exist as
branched chained molecules as shown in the following
example:
CH3 - CH2 – CH - CH2 - CH3
|
CH3

Like hexane, this molecule has molecular formula C6H14
but its structural formula is different making it a different
substance with different melting and boiling points.

It is called a structural isomer of hexane, since it has
the same molecular formula but a different structural
formula.
Isomer starter
Structural isomers have the same
m________ formula but a different
s________ formula. These isomers have
different p_________ p_________ like
m_____ and b______points
Naming alkanes –
Example Name the following alkane
• CH3- CH2- CH - CH2 - CH3
|
CH2-CH2- CH3
Steps in naming alkanes –
1.Identify the longest continuous chain of C atoms.
• CH3- CH2- CH - CH2 - CH3
|
CH2-CH2- CH3
hexane
Steps in naming alkanes –
2. Identify the longest continuous chain of C atoms. This
is called the parent chain 6 C’s ie hexane
Identify any branches off the parent chain.
Number the parent chain to give the branch the lowest
possible number.
1
2
3
CH3- CH2- CH - CH2 - CH3
|
CH2-CH2- CH3
4
5
6
2 carbon ethyl
branch
Steps in naming alkanes –
3. We now write the name as
3 – ethylhexane (don’t forget the hyphen
between letters and numbers and commas
between numbers)
1
2
3
CH3- CH2- CH - CH2 - CH3
|
CH2-CH2CH3
4
5 6
Side chain
3 – ethyl hexane
number
side chain
Parent chain
Names of alkyl side chains
CH3
- methyl
C2H5
- ethyl
C3H7
- propyl
etc - get the idea!
Name the following alkane –
1
2
3
4
5
CH3- CH- CH2 - CH2 - CH3
|
CH3
Side chain
2 – methyl pentane
number
side chain name
Parent chain
Name the following haloalkane –
5
4
3
2
1
CH3- CH2- CH - CH2 - CH3
|
|
CH3
Cl
Which way to
number eh?
What takes priority?
(think alphabetical)
2 – Chloro-2-methylpentane
Name the following alkane (tricky) –
CH3
|
1
3
4
5
CH3- C- CH2 - CH2 - CH3
|2
CH3
2,2-dimethylpentane
What alkane is 2,2-dimethylpentane an
isomer of?
Naming alkanes –
Example Name the following alkane
• CH3- CH2- CH - CH2 - CH3
|
CH2-CH2- CH3
Naming alkanes –
Example Now name the following alkane
CH3
|
CH3- CH2- CH - CH2 – CH2-CH3
|
CH2-CH3
Tricky Task:
Draw and Name all the possible structural isomers
of hexane
Remember a structural isomer has the same
molecular formula but a different structure
Alkane Reactions
Halogenationof an alkane - is the reaction
occurring when a halogen (X) eg bromine,
(Br2),Chlorine (Cl2) or (F2) reacts with an alkane.
The reaction is usually very slow.
But it can be dramatically sped up with the
addition of ultraviolet light (sunlight) which acts
as a catalyst. This is important.
Alkane Reactions
Halogenation of an alkane:
eg Bromine added to ethane
The reaction that occurs is a substitution in which an H
atom is replaced by a Br atom from each Br2 molecule.
H
H
H
C
C
H
H
ethane
H
+
Br2

Only with
UV light!
H
H
H
C
C
H
H
Br +
H-Br
bromoethane
Note: Only one of the Br atoms from each Br2, not both,
is substituted!
ALKENES
Alkenes are unsaturated hydrocarbons.
This is because they contain double C=C bonds
(alkenes).
Alkenes have the general formula CnH2n
H
H
C
H
C
H
H C
C H
The simplest alkene ethene a gas at RT
A different looking alkene
H
H
H
H
H
H
H
H
H
H
Cyclohexene
(C6H10)
Why are these
different to
normal alkanes
and alkenes?
A different looking alkane
H
H
H
H
H
H
H
H
H
H
H
H
Cyclohexane (C6H12)
The first 2 alkene structures are listed below,
name them and give the condensed structural
formula for each
H
C
H
CH2CH2
H
H
H
C
C
H
ethene
H
C
H
Name
Condensed
structural
Formula
H
C
propene
H
CH3CHCH2
H
H
H
H
H
C
C
C
C
H
H
Name
H
But-2-ene
Condensed
structural
Formula
CH3CHCHCH3
H
H
H
H
H
C
C
C
C
H
H
H
H
C
Pent-1-ene CH3CH2CH2CHCH2
H
Draw Hex-3-ene, Hept-2-ene
Draw and name this tricky one
CH3CH2
CH3
C
H3C
C
2,3-dimethylpent-2-ene
CH3
Alkene Properties
Alkenes have very similiar chemical and
physical properties to alkanes
 They are all insoluble in water
 Don’t conduct electricity
 Completely combust to form CO2 andH2O
 Melting and boiling points increase with
carbon chain length
Because of their double bond Alkenes can exist as geometrical
or cis-trans isomers, a special form of isomerism caused by
the non rotation of groups around the double bond
A simple example is but-2-ene.
CH3
H 3C
C
H
H
H 3C
C
C
H
cis - but-2-ene
H
C
CH3
trans -but-2-ene
To exist as geometrical isomers the C atoms at both ends of the
double bond must each have two different groups (or atoms)
attached.
Here’s another example. One of the molecules below have
geometrical isomers the other one won’t can you choose and then
name them
CH3
H 3C
C
H
C
H
H 3C
C
H
cis - but-2-ene
H
C
CH3
trans -but-2-ene
To exist as geometrical isomers the C atoms at both ends of the
double bond must each have two different groups (or atoms)
attached.
Identify whether cis trans isomers occur with in
the following molecules
H3C
CH3
C
Cl
C
Cl
C
CH3
No
H3C
H
C
Cl
C
CH3
Yes
HO
H
C
CH3
Yes
•The reactions of unsaturated hydrocarbons
like alkenes can be classed as either
•combustion
•addition - a molecule is added across the
multiple bond.
Balance the following alkene incomplete combustion
reactions
C2H4(g) +
2 O2(g)
1
1
C3H6(g) +
O2(g)
2
C5H10(g) +
5 O2(g)
 2 CO(g)
+ 2 H2O(g)
 3 C(g)
+
 5 CO(g)
3 H2O(g)
+ 5 H2O(g)
Alkene Addition Reactions
1. Hydrogenation
H3C
H
Pt
C
H
C
+ H2
H
H
Hi
temp
prop-1-ene
H
H
H
C
C
C
H
H
H
propane
H
Alkene Addition Reactions
2. Halogenation - addition of Cl2 or Br2
H3C
H
C
H
C
+ Cl2
H
prop-1-ene
Occurs spontaneously!
H
H
H
H
C
C
C
H
Cl
Cl
H
1,2-dichloropropane
haloalkane
Alkene Addition Reactions
2. Halogenation - addition of Cl2 or Br2
H3C
H
C
H
C
+ Br2
H
prop-1-ene
Occurs spontaneously!
H
H
H
H
C
C
C
H
Br
Br
H
1,2-bromopropane
How to distinguish between alkenes and alkanes
H
Br H
H
H
Br
H
H
H
H
H
H
+ Br2
H
H
H + Br
2
H
H
H
H
H
H
Cyclohexane (C6H12)
addition!
H
1,2-dibromocyclohexane
H
H
H
H
H
H
H
H
H
H
Cyclohexene (C6H10)
H
H
Very fast
H
Br
H
H
H
H
H
H
H
H
H
+ HBr
H Very slow
substitution
bromocyclohexane
Starter draw
1,4-dichloropentane
H
H
H
H
H
H
C
C
C
C
C
H
Cl
H
H
Cl
H
1,2-dibromoethene
One of these exists as geometric isomers
– draw and name both geometric isomers
Br
H
C
C
H
Br
trans-1,2-dibromoethene
H
H
C C
Br
Br
cis-1,2-dibromoethene
Alkanes vs alkenes page 189 in lab book
There is always a question related to this in
almost all yr 12 organic exams
So don’t muck around
Do it!
Alkene Addition Reactions
3. Unsymetrical Molecules such as HCl and H2O can also be
added to alkenes resulting in the formation of two possible
products. e.g. as propene is an unsymetrical hydrocarbon, the
two possible products are:
H3C
H
C
C
+ HBr
H
H
H
prop-1-ene
H3C
C
H
H
prop-1-ene
H
H
C
C
C
H
H H Br
1-bromopropane
H
C
H
+ HBr
H
H
H
H
C
C
C
H Br H
2-bromopropane
H
H3C
C
H
H
C
+ HBr
H
prop-1-ene
H3C
H
C
H
prop-1-ene
+ HBr
H
H
H
C
C
C
H
H
H
C
C
C
H
H H Br 10%
1-bromopropane minor
H
C
H
H
H
H Br H 90%
2-bromopropane major
The major product is the one in which the H atom of HBr
attaches to the C atom on the double bond with the most H
atoms
(Markovnikov’s rule - sometimes called the “rich get richer”). This
means that in the reaction above the major product will be
2-bromopropane.
Can you apply Markovnikov’s rule to the next alkene
addition reaction (hint H2O splits to give an H and OH)
H3C
C
H
H
C
Hi temp
Acid
+ H2O catalyst
H
H
prop-1-ene
H3C
H
C
H
C
H
prop-1-ene
Hi temp
Acid
+ H2O catalyst
H
H
H
H
C
C
C
H
H
H
C
C
C
H
H H OH 10%
propan-1-ol minor
H
H OH H 90%
propan-2-ol major
Another test for alkenes is using aqueous
potassium permanganate
H
H3C
C
H
C
H
H
H
H
H
C
C
C H
H
OH OH
Another important reaction of unsaturated hydrocarbons
is their reaction with dilute aqueous solutions of purple
potassium permanganate, KMnO4.
The alkene is converted to a diol in this reaction.
H3C
C
H
H
C
H
prop-1-ene
purple
acidic
KMnO4
H
H
H
H
C
C
C
H
OH OH
1,2-propandiol
colourless
H
Preparation of Ethene.
The dehydration of ethanol, CH3CH2OH,
by heating it with a dehydrating agent such as
conc sulfuric acid.
conc H2SO4
CH3CH2OH
CH2 = CH2
heat
+
H2O
Make a model of Ethane and ethene
Try and rotate one of the carbons
What do you notice?
Now make ethene and try and do the same
What do you notice?
Alkenes form geometrical isomers
because they cannot rotate around the
double bond
This is very important!
Saturated unsaturated Fat Expt
all students get 2 tts
1.Weigh each TT- record mass
2.Place ½ a pea size of butter in a tt
3.Weigh find mass of butter –record mass of butter
4.Then place same mass of marg in other TT
5.Add Hexane until both butter and marg are in solution
(shake with bungs on)
6.Then add (counting in lots of 10) drops of Br2 water to
butter tube shake with bung on until Br2 totally
decolourises - record number of drops
7.Then add (counting in lots of 10) drops of Br2 water to
marg tube shake with bung on until Br2 totally decolourises
- record number of drops
8.Write down your observations
9.What does this tell you about butter and oil?
Alkenes make up a large
number of common plastics
Many alkene monomers (single
alkene molecules) can be joined
together to form polymers (or
plastics) by a process called addition
polymerisation
The ethene
H
H
C
monomer
C
H
H
H
H
C . .C
H
H
H
H
C. . C
H
H
We can draw the
ethene molecule
with one of the
bonds in the
double bond as
two electrons so
it looks like this
The process involves the breaking of the double bond in each
alkene molecule, each of the two electrons from the bond go to
each end of the molecule to create a bond with another molecule
that has undergone the same process. This creates long chains
of joined monomers which create a polymer.
H
H
H
H
H
H
C. . C
C. . C
C. . C
H
H
H
H
H
3 ethene
monomers
H
Heat and a catalyst added
H
H
H
H
H
H
C. . C
C. . C
C. . C
H
H
H
H
H
H
Makes polyethene
Aka polyethylene : a
plastic used in pipes
and plumbing fittings
Changing the alkene
CH3 H
monomer creates a
C
C
H
H
Propene monomer
new polymer
CH3 H
CH3 H
CH3 H
C. . C
C. . C
C. . C
H
H
H
H
H
Repeating
monomer unit
CH3 H
C. . C
H
H
Heat and a catalyst added
CH3 H
C. . C
H
H
H
CH3 H
Makes polypropene
C. . C
Aka polypropylene
H
H
Used in plastic coke
bottles and polar fleece
Changing the side chain of the monomer in the
reaction gives different polymers ie
Cl
H
Cl
H
Cl
H 3 chloroethene
(aka vinyl
C chloride)
monomers
C. . C
C. . C
C. .
H
H
H
Repeating
monomer
unit
Cl
Cl H
H
H
H
Heat and a catalyst added
Cl
H
H
Cl
H
H
C
C. . C
C
C. . C
C
C
C . .C
C
H
H
H
H
H
H
H
H
H
H
H
H
Polyvinylchloride
Polymer
Aka PVC used in glues
and many manufacture
plastics
Haloalkanes
This family is essentially an alkane where one hydrogen
atom has been replaced by a halogen (X) (usually chlorine,
bromine,iodine or fluorine ). Haloakanes are non polar and
are not soluble in water.
Haloalkanes are named by using the prefixes chloro,
bromo etc using numbers where necessary to indicate on
which carbon the halogen is located, as shown in the
example below.
H
H3C
Name ?
H
H
H
H
CH2 CH2 CH3
C
H
C C C C C
HC CH2
CH3
H Cl H CH3 H
Cl
2-chloro-4-methylhexane
H
C
H
H
Aphabetical
order
ALKENES AND ALKYNES
Alkenes and alkynes are both families of unsaturated
hydrocarbons.
This is because they contain double C=C bonds (alkenes)
or triple CC bonds (alkynes).
Alkenes with one double bond have the general formula
CnH2n (all have empirical formula CH2), while alkynes with
one triple bond have the general formula CnH2n-2.
H
H
C
H
C
H C
C H
H
Ethene a gas at RT
Ethyne a gas at RT
Commonly called acetylene
Alkynes
H
C
C
H
ethyne
H3C
C
C
H
propyne
H3C
C
C
but-2-yne
CH3
Name?
H3C
CH2
C
H
H
C
H
but-1-ene
(number from RHS as this gives
double bond the lowest number)
Alkyne Reactions
H
C
C
H
Br2 H
C
Br
ethyne
H
Br2
C
Br
Br
H C
Br
Br
C H
Br
cis1,2-dibromoethene 1,1,2,2-tetrabromoethane
H
C
C
ethyne
H+/
H
H
C
KMnO4
OH
H
C
H+/
OH KMnO4
OH
OH
H C
OH
C H
OH
cis1,2-ethene-diol
1,1,2,2-tetrahydroxyethane
Haloalkanes
This family is essentially an alkane where one hydrogen atom
has been replaced by a halogen (usually chlorine or bromine).
The resulting C – Cl bond is slightly polar which makes the overall
molecule slightly polar. Apart from the first two, haloakanes are
not polar enough to be soluble in water.
Haloalkanes are named by using the prefixes chloro, bromo
etc using numbers where necessary to
indicate on which
carbon the halogen is located, as shown in
CH CH CH CH
H C HC CH
the example
below.
Cl
CH
3
2
2
2
3
3
2-chloro-4-methylpentane
H3C
HC
Cl
CH2
CH CH2 CH2 CH3
CH3
Exercise 1: Draw the structural formulae for each of the
following molecules.
2,3-dimethylpentane
3-ethyl-2-methylheptane
2,2,4-trimethylhexane
Preparation of ethyne (lets have a break and
make some ethyne)
Write the structural formula for ethyne
In the laboratory ethyne is prepared by the reaction of
water with calcium carbide.
CaC2(s)
+
2H2O(l) 
C2H2(g) + Ca(OH)2(aq)
The ethyne produced is collected by the downward
displacement of water.
Turn to page 204 in your lab book and read the
instructions carefully
Properties of Alkynes page 204 in lab
book
Read instructions carefully
Make ethyne by the following reaction
CaC2 + 2H2O
Ca(OH)2 + C2H2
Then carry tests out for alkynes
ALCOHOLS
•Alcohols are a homologous series of
molecules that have the -O-H functional group.
• They are named as for alkanes but with the
final -e replaced by ol.
•Smaller alcohols are polar because of polar
• –OH group and are soluble in polar solvents
•Smaller alcohols are liquids at room
temperature
ALCOHOLS
H
H
CH3OH
methanol
CH3CH2OH
ethanol
C OH
H
H
H C
H
H
H C OH
H H
H
H C C OH
H
C OH
H
H H
H HH
H C C C OH
H H H
H H H
H
H3C
C
CH3
H
propan-1-ol
OH
H C C C OH
H H H
CH3CH2CH2OH
H3C
C
propan-2-ol
CH3
OH
CH3CHOHCH2OH
Name and label each of the following alcohols as primary,
secondary or tertiary.
tertiary
H3C
OH
C
CH3CH2CH2OH
primary
Propan-1-ol
CH3
CH3
2-methylpropan-2-ol
CH2
H3C
CH3
CH
CH2
OH
H3C
CH3
CH
OH
Butan-2-ol
secondary
Draw and Name the following
CH3
H3C HC
HC
CH
C
CH
CH3
CH3
H3C CH CH CH
2
CH2
2-methylhex-3-ene
CH3
•propyne
CH
5-methylhex-2-ene
CH3
Alcohols are classified as
primary (1°), secondary
(2°), or tertiary (3°),
according to the number
of carbon atoms bonded
to the carbon atom
attached to the –OH
group.
Methanol is considered a
1° alcohol.
Each class of alcohols has
characteristic chemical
properties.
Oxidation of Alcohols
Primary alcohols can be oxidised to form carboxylic acids. For
example when ethanol is oxidised by an acidified solution of
potassium dichromate it is converted to ethanoic acid, CH3COOH,
a carboxylic acid.
The equation for the oxidation of the primary alcohol ethanol is
CH3CH2OH(l)
CH3COOH(l)
Acidified
potassium
dichromate
H+/ K2Cr2O7
Cr2O72-
Orange
Cr 3+
Green
This colour
change is
important
Oxidation of alcohols – primary alcohols can
be oxidised to form carboxylic acids
Ethanol
Acidified
potassium
dichromate
Ethanoic acid
H+/ Cr2O72-
CH3CH2OH
CH3COOH
O
This is the
carboxylic
functional
group
C
R
OH
When this reaction occurs, the colour change observed is from
orange, (colour of dichromate ion Cr2O72), to green (colour of
Cr3+). (This is the reaction observed in a positive test using
the old breathalyser).
Oxidation of alcohols
Primary and secondary alcohols are oxidised by acidified
potassium dichromate. (changes from orange to green)
A beaker of hot water speeds up the reaction.
There is no reaction with tertiary alcohols.
Oxidation of Primary Alcohols
H+/ Cr2O72-
H+/ Cr2O72-
Aldehydes are the
intermediate
product – smell
detected these are
not examinable at
yr12
Cr 3+
Oxidation of Secondary Alcohols
H+/ Cr2O72-
Cr 3+
Smell detected
Know this reaction occurs. You do not need to
know the structure of a ketone at yr12
Tertiary Alcohols do not oxidise
Draw structural formulae for these compounds and
classify any alcohols as primary, secondary or tertiary :
butan-2-ol
Secondary alcohol
H
Oxidises to ketone
3-methylpentan-1-ol
Primary alcohol
H
H
H
H
C
C
C
C
H
H
OH H
H
Oxidises to carboxylic acid
2-methylhexan-2-ol
Tertiary alcohol
Does not oxidise
H
H
H
H
H
H
H
C
C
C
C
C
H
H
CH3 H
H
OH
H
H
H
H CH3 H
C
C
C
C
C
H
H
H
H
OH H
C
H
Properties of Alcohols:
As the non-polar alkyl chain increases in length the molecules
become more non-polar and increasingly insoluble in water. Like
the hydrocarbons, the melting and boiling points increase with
molar mass.
Important Alcohol Reactions
Ethanol is produced by anaerobic (without oxygen) fermentation
of sugars in cereals, grapes, sugar beet etc. This is the method of
producing ethanol for drinking in wine, beer etc.
yeast
C6H12O6(aq)

2CO2(g) + 2CH3CH2OH(aq)
Hydration of ethene (ie adding an – OH) using a catalyst, high
temperature and pressure. This is the method of producing
industrial ethanol.
CH2 = CH2(g) + H2O(g)

CH3CH2OH(g)
2,2-dichloro – 3,3-diiodoheptanol
Draw
these
structures
and
classify
them
H
Primary alcohol
H
H
H
H
I
Cl
H
C
C
C
C
C
C
C
H
H
H
H
I
Cl
H
2,3-dibromohexene
H
H
H
H
Br Br
H
C
C
C
C
C
H
H
H
H
C
H
alkene
OH
Properties of Alcohols:
The smallest alcohols are all liquids and are soluble in
water (because of the polar O-H bond).
Polar
–OH bond
Intermolecular hydrogen
bond
Demo oxidation of alcohols
CARBOXYLIC ACIDS
molecules containing the functional group - COOH, or written
structurally as
O
C
R
OH
Carboxylic Acids
•When naming carboxylic acids it is important to remember
to include the C atom of the COOH group when finding the
parent name.
•The systematic name is the parent alkane with the -e
removed and replaced by -oic acid.
•NOTE: A number is not needed to locate the COOH group
as the chain is always numbered from the C of the COOH
CH3CH2COOH
propanoic acid
Structural formula
Name
Condensed
Structural
Formula
O
H
C
methanoic acid
HCOOH
propanoic
CH3CH2COOH
butanoic acid
CH3CH2CH2COOH
OH
O
CH3CH2 C
OH
O
CH3CH2CH2 C
OH
How do you make the following name all
compounds and reagents and observations
propanol (primary alcohol)
CH3CH2CH2OH(l)
propanoic acid
CH3CH2COOH(l)
Acidified
potassium
dichromate
H+/ Cr2O72Cr2O72-
Orange
Cr 3+
Green
Carboxylic Acid Properties
Short chain carboxylic acids are soluble in water
because the COOH group is polar. As the alkyl chain
increases in length the acids become increasingly
non-polar and less soluble in water.
Exercise: Draw the structural formula for:
3,3-dichlorobutanoic acid
Cl
O
CH3C CH2 C
OH
Cl
2-hydroxypropanoic acid.
OH
CH3CH
O
C
OH
2,2-dichloro-3,4-dimethylpentanol
H
H
H CH3 Cl
H
C
C
C
C
C
H
CH3 H
Cl
H
OH
Carboxylic Acid Properties
Like all acids, aqueous solutions of carboxylic acids have the
following properties.
They turn blue litmus pink.
They conduct electricity as the dissociation in water
produces ions that are free to move.
They react with metals forming hydrogen gas and a solutio
of the metal salt. The reaction equation can be written as
follows:
2CH3COOH(aq) + Mg(s)  Mg(CH3COO)2(aq) + H2(g)
They also react with carbonates to give a salt CO2 and water
ESTERS
Carboxylic acids react with alcohols, in the presence of
concentrated sulfuric acid as a catalyst, to form esters.
The reagents are heated together to bring about a reaction
Any excess acid is neutralised by the addition of sodium
carbonate. If ethanoic acid is reacted with methanol the
ester, methyl ethanoate is formed.
O
H3C
C
methanol
H C C
O
O
3
O
HCH3O+
3
+ CH3OH
OH
ethanoic acid
heat
H3C
C
+ H2O
O
CH3
methyl ethanoate
Alcohol – carboxylic acid
1)Write equations using structural formulae for the
formation of the following esters
a) ethyl methanoate from ethanol and methanoic acid
b) butyl propanoate from butan-1-ol and propanoic acid
Many esters occur naturally and can often be identified
by their fruity odour, although they may also smell like
glue, nail polish remover, linament or blue cheese.
Many are used as flavourings and perfumes.
Esters are non polar and will from a layer when added to
water
2)Name the ester that would be formed by reacting
a) propan-1-ol and ethanoic acid
propylethanoate
b) butanoic acid and methanol
methylbutanoate
Name the alcohol and carboxylic acid that would react
together to form
ethyl pentanoate
pentanoic acid
butyl octanoate
octanoic acid
Hydrolysis of esters
The hydrolysis (breaking up) of an ester results in the formation of
an alcohol and the carboxylic acid
(a)Hydrolysis in acid produces the alcohol + carboxylic acid
CH3CH2COOCH3
+
methyl propanoate
H2O / H+ 
CH3CH2COOH + CH3OH
propanoic acid
methanol
(b) Hydrolysis in NaOH or KOH solution gives alcohol + the
sodium salt of the carboxylic acid.
CH3CH2COOCH3 + NaOH  CH3CH2COONa+ + CH3OH
methyl propanoate
sodium propanoate
methanol
Fats and oils
Fats and oils (lipids) are all triesters made from glycerol
(propane-1,2,3-triol) and three long chain carboxylic acids (fatty
acids) as shown below.
Glycerol is an example of a ”triol” which has three -OH groups
present. Each of these can form an ester link with a different
carboxylic acid.
O
H
H C
OH
+ R1COOH
H C
OH
+ R2COOH 
H C
OH
H
Glycerol
H2C
O
C
O
R1
O
HC
C
O
R2
O
C
R3
+ R3COOH
H2C
3 fatty acids
+ 3H2O
Oil or Fat (triester)
Soap
The three ester links present in these molecules can be
broken (or hydrolysed) by heating with sodium hydroxide
solution.
This releases the original glycerol molecule plus the
sodium salts of the long chain fatty acids which are
soaps. This “saponification” process is shown in the
diagram below.
O
H2C
O
HC
O
C
O
H2C
O
C
H2C
HC
H2C
R1
C
O
OR
2
R3
O
O
H
O
C
O
R1
C
O
R2
C
R3
H C
OH
H C
OH
H C
OH
H
+ 3NaOH
Heat
H
+ R1COONa+
H C
OH
H C
OH + R 2COONa+
H C
OH
H
+ R 3COONa+
3 soap molecules
Soaps work because the tail of the molecule is a long
non-polar hydrocarbon chain (from the fatty acid) which
readily dissolves grease and dirt (as “like dissolves
like”). Then the ionic carboxylate ion readily dissolves in
water (which is also polar) and is able to carry away the
grease with it in the rinse water.
_
Na+ HO
O
CH2
C
CH2
CH2
CH
CH2
CH2
CH
CH
CH
CH2
CH2
CH2
CH2
O
polar carboxylate
head (dissolves in
water)
non-polar hydrocarbon
tail (dissolves grease/dirt)
CH3
CH2
Soaps work because the tail of the molecule is a long
non-polar hydrocarbon chain (from the fatty acid) which
readily dissolves grease and dirt (as “like dissolves
like”). Then the ionic carboxylate ion readily dissolves in
water (which is also polar) and is able to carry away the
grease with it in the rinse water.
HO
CH2
C
CH2
CH2
CH
CH2
CH2
CH
CH
CH
CH2
CH2
CH2
CH2
O
polar carboxylate
head (dissolves in
water)
non-polar hydrocarbon
tail (dissolves grease/dirt)
CH3
CH2